STATUTORY INSTRUMENTS. S.I. No. of 2011 BUILDING REGULATIONS (PART A AMENDMENT) REGULATIONS 2011

Transcription

1 STATUTORY INSTRUMENTS S.I. No. of 2011 BUILDING REGULATIONS (PART A AMENDMENT) REGULATIONS 2011 (Prn. / )

2 S.I. No. of 2011 BUILDING REGULATIONS (PART A AMENDMENT) REGULATIONS 2011 I, XXXX XXXXXX, Minister for the Environment, Heritage and Local Government, in exercise of the powers conferred on me by sections 3 and 18 of the Building Control Act 1990 (No. 3 of 1990), hereby make the following regulations: - Citation 1. (1) These Regulations may be cited as the Building Regulations (Part A Amendment) Regulations (2) These Regulations and the Building Regulations 1997 (S.I. No. 497 of 1997) may be cited together as the Building Regulations 1997 to 2011 and shall be construed together as one. Commencement 2. Subject to Regulation 3, these Regulations shall come into operation on 1 January Application 3. These Regulations shall apply to works, or buildings in which a material alteration or change of use takes place, where the works, material alteration or change of use takes place, as the case may be, on or after 1 January Amendments to the Building Regulations The Building Regulations 1997 are amended by substituting for Part A of the Second Schedule the following: - PART A STRUCTURE Loading. A1 (1) A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that the loadings that

3 are liable to act on it are sustained and transmitted to the ground: - (a) (b) safely, and without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building. (2) In assessing whether a building complies with subparagraph (1), regard shall be had to the variable actions to which it is likely to be subjected in the ordinary course of its use for the purpose for which it is intended. Ground movement. A2 A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that movements of the subsoil caused by subsidence, swelling, shrinkage or freezing will not impair the stability of any part of the building. Disproportionate A3 (1) A building shall be designed and constructed, with collapse due regard to the theory and practice of structural engineering, so as to ensure that in the event of an accident the structure will not be damaged to an extent disproportionate to the cause of the damage. (2) For the purposes of subparagraph (1), where a building is rendered structurally discontinuous by a vertical joint, the building on each side of the joint may be treated as a separate building whether or not such joint passes through the substructure. Definitions for A4 In this Part: this Part. loadings on the building will comprise actions that may be applied both separately and in various combinations; actions means: (a) (b) a set of forces (loads) applied to the structure (direct action), a set of imposed deformations or accelerations (indirect actions).

4 Given under my Official Seal, XX XXXXXX XXXX XXXXXX, Minister for the Environment, Heritage and Local Government.

5 EXPLANATORY NOTE (This note is not part of the Instrument and does not purport to be a legal interpretation.) These Regulations amend Part A of the Building Regulations 1997 (S.I. No 497 of 1997) and are necessary to ensure consistency with the Structural Eurocodes (i.e. a set of harmonised structural design codes for building and civil engineering works) in Ireland. The Regulations come into effect on 1 January 2012.

6 A PUBLIC CONSULTATION DRAFT February 2011 Structure Building Regulations 2011 Technical Guidance Document

7 Contents Building Regulations 2011 Technical Guidance Document A Structure Page Introduction 3 The Guidance 3 Existing Buildings 3 Technical Specifications 3 Materials and Workmanship 4 Interpretation 4 Part A: The Requirement 5 Section 1 Structure Loading and ground movement 6 Introduction 6 Other approaches 7 Definitions 8 Sub-section 1 Sizes for certain structural elements for houses and other small buildings Part 1 Basic requirements for stability Part 2 Sizes of certain timber floor, ceiling and roof members in houses 9 Application 9 The use of this part Part 3 Thickness of walls in houses with not more than two floors including the ground floor 1x Application 1x The use of this part 1x Wall types 1x Wall construction 1x External walls 1x Internal load-bearing walls 1x Materials 1x Maximum loads 1x Wind loads 1x Retained earth 1x Limitations on building geometry 1x Lateral support and end restraint 1x Buttressing 1x Openings and chases in walls 1x Interaction of elements 2x 1

8 Contents Part 4 Proportions for masonry chimneys above the roof surface Height to width relationship 2x 2x Part 5 Strip foundations of plain concrete 2x Conditions relating to the sub-soil 2x Design provisions 2x Minimum width of strip foundations 2x Sub-section 2 Design and construction of all building types - codes, standards and references Introduction Codes, standards and references Sub-section 3 Recovering of existing roof structures and structural safety of external wall cladding Recovering of existing roof structures Structural safety of external wall cladding Technical approach Codes and standards Section 2 Disproportionate collapse Codes and standards Additional information Introduction Disproportionate collapse Determine building consequence class Assess additional measures Design and construct additional measures Definitions Standards and publications other references 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 4x 2

9 Building Regulations Technical Guidance Document A - Structure Introduction This document has been published by the Minister for the Environment, Heritage and Local Government under article 7 of the Building Regulations It provides guidance in relation to Part A of the Second Schedule to the Regulations. The document should be read in conjunction with the Building Regulations , and other documents published under these Regulations. In general, Building Regulations apply to the construction of new buildings and to extensions and material alterations to buildings. In addition, certain parts of the Regulations apply to existing buildings where a material change of use takes place. Otherwise, Building Regulations do not apply to buildings constructed prior to 1 June, Transitional Arrangements In general, This document applies to works, or buildings in which material changes of use takes place, where the works or the change of use commence or take place, as the case may be, on or after 1 January Technical Guidance Document A - Structure, dated also ceases to have effect from that date. However, the latter document may continue to be used in the case of works, or buildings in which a material change of use takes place - (a) (b) where the works or the change of use commence or takes place, as the case may be, before 31 December 2011, in respect of which a Fire Safety Certificate under the Building Control Regulations, 1991 to 1994, has been granted, where the works or change of use commence or takes place, as the case may be, not later than 31December, The Guidance The materials, methods of construction, standards and other specifications (including technical specifications) which are referred to in this document are those which are likely to be suitable for the purposes of the Regulations. Where works are carried out in accordance with the guidance in this Document, this will, prima facie, indicate compliance with Part A of the Second Schedule to the Building Regulations. However, the adoption of an approach other than that outlined in the guidance is not precluded provided that the relevant requirements of the Regulations are complied with. Those involved in the design and construction of a building may be required by the relevant building control authority to provide such evidence as is necessary to establish that the requirements of the Building Regulations are being complied with. Existing Buildings In the case of material alterations or changes of use of existing buildings, the adoption without modification of the guidance in this document may not, in all circumstances, be appropriate. In particular, the adherence to guidance, including codes, standards or technical specifications, intended for application to new work may be unduly restrictive or impracticable. Buildings of architectural or historical interest are especially likely to give rise to such circumstances. In these situations, alternative approaches based on the principles contained in the document may be more relevant and should be considered. Technical Specifications Building Regulations are made for specific purposes, e.g. to provide, in relation to buildings, for the health, safety and welfare of persons, the conservation of energy and access for people with disabilities. Technical specifications (including harmonised European Standards, European Technical Approvals, National Standards and Agrément Certificates) are relevant to the extent that they relate to these considerations. Any reference to a technical specification is a reference to so much of the specification as is relevant in the context in which it arises. Technical specifications may also address other aspects not covered by the Regulations. A reference to a technical specification is to the latest edition (including any amendments, supplements or addenda) current at the date of publication of this Technical Guidance 3

10 Building Regulations Technical Guidance Document A - Structure Document. However, if this version of the technical specification is subsequently revised or updated by the issuing body, the new version may be used as a source of guidance provided that it continues to address the relevant requirements of the Regulations. Materials and Workmanship Under Part D of the Second Schedule to the Building Regulations, building work to which the Regulations apply must be carried out with proper materials and in a workmanlike manner. Guidance in relation to compliance with Part D is contained in Technical Guidance Document D. Interpretation In this document, a reference to a section, subsection, part, paragraph or diagram is, unless otherwise stated, a reference to a section, subsection, part, paragraph or diagram, as the case may be, of this document. A reference to another Technical Guidance Document is a reference to the latest edition of a document published by the Minister for the Environment, Heritage and Local Government under article 7 of the Building Regulations Diagrams are used in this document to illustrate particular aspects of construction - they may not show all the details of construction. 4

11 Structure Part A - The Requirement Part A of the Second Schedule to the Building Regulations, (as amended), provides as follows: Loading. A1 (1) A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that the so as to ensure that the combined dead, imposed and wind loads loadings that are liable to act on it are sustained and transmitted to the ground - (a) (b) safely, and without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building. (2) In assessing whether a building complies with sub-paragraph (1), regard shall be had to the imposed loads and wind loads variable actions to which it is likely to be subjected in the ordinary course of its use for the purpose for which it is intended. Ground movement. A2 A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that movements of the subsoil caused by subsidence, swelling, shrinkage or freezing will not impair the stability of any part of the building. Disproportionate Collapse. A3 (1) A multi-storey building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that in the event of an accident the structure will not be damaged to an extent disproportionate to the cause of the damage. (2) For the purposes of sub-paragraph (1), where a building is rendered structurally discontinuous by a vertical joint, the building on each side of the joint may be treated as a separate building whether or not such joint passes through the substructure. Definitions for this A4 In this Part - Part. dead load" means the force due to the static mass of all walls, permanent partitions, floors, roofs and finishes including all other permanent construction and services equipment affixed to the building; "imposed load" means the load assumed to be produced by the intended occupancy or use of the building including distributed, concentrated, impact, inertia and snow loads and the force due to the static mass of moveable partitions, but excluding wind loads; "multi-storey building" means a building comprising or including five or more storeys, a basement storey being regarded as a storey; "storey" means any of the parts into which a building is divided horizontally above or below ground level but excluding any part of a building situated above the level of the roof or in the roof space, or below the level of the lowest floor, which is intended for the protection of a water tank, or lift motor, or similar use and is not intended for, or adapted to be used for habitable purposes, or as a work room, or as a store room; Loadings on the building will comprise actions that may be applied both separately and in various combinations. actions means: (a) a set of forces (loads) applied to the structure (direct action) (b) a set of imposed deformations or accelerations (indirect actions) 5

12 Section 1 Structure Loading and ground movement This Technical Guidance Document is divided into two sections. Section 1 relates to the requirements in A1 and A2. Section 2 relates to the requirement in A3. Section 1 Structure - Loading and ground movement Loading. A1 (1) A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that the dead, imposed and wind loads loadings that are liable to act on it are sustained and transmitted to the ground - (a) (b) safely, and without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building. (2) In assessing whether a building complies with sub-paragraph (1), regard shall be had to the imposed loads and wind loads variable actions to which it is likely to be subjected in the ordinary course of its use for the purpose for which it is intended. Ground movement. A2 A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that movements of the subsoil caused by subsidence, swelling, shrinkage or freezing will not impair the stability of any part of the building. Introduction The safety of a structure depends on the successful combination of design and completed construction, particularly: (a) (b) (c) (d) (e) The design should be based on identification of the hazards to which the structure is likely to be subjected and assessment of risks. The selection of relevant critical situations for design should be made reflecting the conditions that can reasonably be foreseen during future use; loading, properties of materials, design analysis, details of construction, (f) (g) safety factors, workmanship. As regards (a), the reliability of designs carried out in accordance with the Eurocodes is based on a number of assumptions set out in I.S. EN 1990: 2002 that include: the choice of the structural system and the design of the structure is made by appropriately qualified and experienced personnel; the design and construction is carried out by personnel having the appropriate skill and experience; adequate supervision and quality control is provided during execution of the work; 6

13 Section 1 Structure Loading and ground movement the construction materials and products are used as specified in I.S. EN 1990 or in I.S. EN 1991 to I.S. EN 1999 or in the relevant execution standards, or reference material or product specifications; the structure will be adequately maintained; and the structure will be used in accordance with the design assumptions. As regards (b) (a), the loadings to which a building is subjected should be calculated in accordance with the appropriate Structural Eurocodes: (i) for densities, self weight and imposed loadings, I.S. EN :2002 (Eurocode 1); (ii) for accidental actions; I.S. EN : 2006 (Eurocode 1); (iii) for snow loadings, I.S. EN :2003 (Eurocode 1); (iv) for wind loadings, I.S. EN :2005 (Eurocode1); (v) for earth retaining structures, I.S. EN :2004 (Eurocode 7) (vi) any greater loadings to which the building is likely to be subjected (Eurocode 1). Any reference to the European Standards for Structure (Structural Eurocodes) must be taken to include reference to the relevant Irish National Annex. The use of the Eurocodes referenced in this document is a practical guidance on meeting the Requirements of Part A. A full list of the relevant Eurocodes is included in the Standards and publications section of this Technical Guidance Document and references are made in text where appropriate. dead and imposed loads, other than imposed roof loads, should be in accordance with BS 6399: Part 1. Imposed roof loads should be in accordance with BS 6399 : Part 3, using the snow load map shown in Diagram 14 of this Technical Guidance 7 Document. Snow load Wind loads should be in accordance with CP3: Chapter V: Part 2, using wind speeds based on Diagram 15 of this Technical Guidance Document or BS 6399: Part 2 using win speeds based on Diagram 15A of this Technical Guidance Document This Section is comprised of three subsections: Sub-section 1 of the document applies to small buildings with walls of traditional masonry construction and with timber first floors and roofs. It gives sizes for certain elements in houses with not more than two floors including the ground floor. This subsection also applies to domestic garages and other annexes attached to such houses. The sub-section is arranged in five parts as follows: Part 1: - Basic requirements for stability. Part 2: - Sizes of certain timber floor, ceiling and roof members in houses with not more than two floors, including the ground floor. Part 3: - Thickness of masonry walls in houses with not more than two floors including the ground floor. Part 4: - Proportions for masonry chimneys above the roof surface. Part 5: - Strip foundations of plain concrete. Part 1 gives general rules which must be observed in using Parts 2 and 3. Parts 2 to 5 may be used independently of each other. Sub-section 2 is relevant to all building types and lists standards for structural design and construction but, where these do not give precise guidance, regard should be had to par Sub-section 3 provides guidance for recovering of existing roof structures and the structural safety of external wall cladding Other approaches If other approaches are adopted, it is essential to have regard to par and to the following:

14 Section 1 Structure Loading and ground movement (a) (b) The numerical values of safety factors, whether expressed explicitly or implicitly in design equations or design values, should be derived from considerations of the aspects of design and construction given in par as a whole. A change in any one of these aspects may affect the safety of the structure; Loads used in calculations should allow for possible dynamic, concentrated and peak load effects that may occur. The design should ensure that the effects of actions do not cause a situation of irreversible limit states (Refer to I.S. EN 1990:2002) Definitions The following definitions apply to sub-sections 1 to 3: Buttressing wall - A wall designed and constructed to afford lateral support to another wall perpendicular to it, support being provided from the base to the top of the wall. Cavity width - the horizontal distance between the two leaves of a cavity wall. Compartment wall - A wall constructed as a compartment wall to meet the requirements of Part B (Fire Safety) of the Second Schedule to the Building Regulations. Pier - A member which forms an integral part of a wall, in the form of a thickened section, so as to afford lateral support to the wall to which it is bonded or securely tied. Separating wall - A wall or part of a wall which is common to adjoining buildings and constructed to meet the requirements of Part B (Fire Safety) of the Second Schedule to the Building Regulations. Spacing - The distance between the longitudinal centres of any two adjacent members of the same type, measured in the plane of floor, ceiling, roof, or other part of the structure of which members form a part. Span - The distance measured along the centre line of a member between the centres of any two adjacent bearings or supports. 8 Note: The spans given in Part 2 of sub-section 1 of this Section for floor joists, rafters, purlins and ceiling joists are as defined in SR 11: Supported wall - A wall to which lateral support is afforded by a combination of buttressing walls, piers or chimneys acting in conjunction with floor(s) or roof. Actions (a) a set of forces (loads) applied to the structure (direct action); (b) a set of imposed deformations or accelerations (indirect actions). Actions are classified by their variation in time and include the following (For full definitions of all terminology relating to actions and other action types refer to I.S. EN 1990): Permanent action (G) - action that is likely to act throughout a given reference period and for which the variation in magnitude with time is negligible, or for which the variation is always in the same direction (monotonic) until the action attains a certain limit value e.g. selfweight of structures, fixed equipment etc. and indirect actions caused by e.g. shrinkage and uneven settlements etc. Variable action (Q) - action for which the variation in magnitude with time is neither negligible nor monotonic e.g. imposed loads on building floors etc, wind actions or snow loads ; Accidental action (A) - action, usually of short duration but of significant magnitude, that is unlikely to occur on a given structure during the design working life e.g. explosions, or impact from vehicles, etc. Imposed load - Imposed loads on buildings are those arising from occupancy e.g. normal use by persons, furniture and moveable objects (e.g. moveable partitions, storage),vehicles, anticipating rare events, such as concentrations of persons or of furniture, or the moving or stacking of objects which may occur during reorganization or redecoration. Self-weight - includes the structure and nonstructural elements including fixed services as well as the weight of earth and ballast. Non-structural elements include roofing, surfacing and coverings, partitions, suspended ceilings, wall cladding, thermal insulation, fixed services e.g..electrical, plumbing, heating, ventilating, air conditioning etc.

15 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Sub-section 1 Sizes for certain structural elements for houses and other small buildings Part 1 - Basic requirements for stability This Part must be used in conjunction with Parts 2 and 3 of this sub-section Trussed rafter roofs should be braced to the recommendations of I.S. 193: SWiFT 5:2011 (formerly called I.S. 193: This document is currently under preparation and is due to be republished as Non Contradictory Complimentary Information to the Eurocodes). Where, due to its form of construction, a traditionally framed roof (i.e. using rafters, purlins and ceiling joists) does not have sufficient built-in resistance to instability, for example from hipped returns, then bracing is required If the roof structure is braced as described above and adequately anchored to the structure beneath and the walls are designed and restrained in accordance with the requirements of Part 3 of this sub-section, no special provision should be needed to take account of loads due to the effect of wind pressure or suction. However, par gives details of situations in which additional ties may be required. Part 2 - Sizes of certain timber floor, ceiling and roof members in houses Application This Part applies only to houses (Category A1 buildings as defined in I.S. EN ) with not more than two floors including the ground floor. The use of this Part This Part must be used in conjunction with Part 1 of this sub-section The guidance given in this Part assumes that: (a) the dead and imposed loads permanent and variable actions to be sustained by the floor, ceiling or roof of which the member forms part do not exceed the (b) (c) values given in SR 11:1988 the loadings calculated in accordance with the appropriate Structural Eurocode. Alternatively, safe load span tables in SWiFT 6, (formerly called I.S ), if applicable, may be used. Note: this document is currently under preparation and is due to be republished as Non Contradictory Complimentary Information to the Eurocodes). the species of timber and grade combinations for allocation to strength classes are those given in I.S. EN 1912)SR 11 : 1988, (Note: RS Grade as per I.S. 127 is not included in I.S. EN 1912) and, the strength class is in accordance with I.S. EN 338 (d) floor boarding complying with BS 1297: 1987 is used Except where indicated, the cross sectional dimensions given in SR 11: 1988 are basic sawn sizes as defined in BS 4471: Part 1: SR 11: 1988 does not apply where these basic sawn dimensions have been reduced by regularising or planing. For timber of North American origin, SR 11 : 1988 applies only as indicated to surfaced sizes unless the timber has been resawn to BS 4471 requirements. Target sizes and permissible deviations should be in accordance with I.S. EN Notches and holes in simply supported floor and roof joists should be within the following limits: (a) notches should be no deeper than times the depth of a joist and should not be cut closer to the support than 0.07 times the span, nor further away than 0.25 times the span, (b) holes should be no greater diameter than 0.25 times the depth of the joist, should be drilled at the neutral axis, should be not less than three diameters (centre to centre) apart and should be located 9

16 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings (c) between 0.25 and 0.4 times the span from the support, and the horizontal distance between any hole and any notch should not be less than the depth of the joist Bearing areas and workmanship should comply with the relevant requirements of I.S. EN BS 5268: Part 2: Refer also to paragraphs to of this document Timber joists, rafters and purlins should be designed in accordance with SR 11: 1988 I.S. EN for the loadings calculated in accordance with the appropriate Structural Eurocode.. Alternatively safe load span tables in SWiFT 6 may be used. Part 3 - Thickness of masonry walls in houses with not more than two floors including the ground floor Application This Part applies to houses (Category A1 buildings as defined in I.S. EN ) with not more than two floors including the ground floor, with walls of traditional masonry construction, with timber upper floors and with roofs covered with normal lightweight covering including clay or concrete pantiles. It also applies to domestic garages and other annexes attached to such houses. For the design of timber framed houses refer to I.S. 440: 2009 The use of this Part This Part must be used in conjunction with Part 1 of this sub-section. All appropriate design conditions given in this part must be satisfied. Walls should comply with the relevant requirements of I.S. EN 1996 for loadings calculated in accordance with the appropriate Structural Eurocode. I.S. 325: Part 2: The wall types given in par may be constructed as described in par using the materials described in par and subject to the requirements of pars to Wall Types This Part applies to external walls and internal walls (including compartment walls and separating walls) Wall Construction (a) External walls (i) Cavity walls constructed using two leaves composed of either, solid concrete blocks or bricks of not less than 100 mm thickness, or of clay bricks, tied together with wall ties appropriate to the width of cavity. The inner leaf may be constructed using 100 mm thick lightweight solid concrete blocks. (b) (ii) Cavity block walls constructed using 215 mm hollow concrete blocks. Internal load bearing walls (i) Internal load bearing walls composed of solid or lightweight solid concrete blocks or bricks. (ii) Separating walls composed of 215 mm thick solid concrete blocks or bricks (refer to Technical Guidance Document E for guidance on sound insulation). (iii) Separating walls of cavity construction composed of two leaves of solid or lightweight solid concrete blocks or bricks of not less than 100 mm thickness or of clay bricks (refer to Technical Guidance Document E for guidance on sound insulation). Materials The materials used should meet the following minimum designations, strengths and other qualities. Any reference to the European Product Standards must be taken to include reference to the relevant Irish National Annex. 10

17 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Masonry units Walls should be properly bonded and solidly put together with mortar and constructed of masonry units conforming to Table 1 below: Table 1 Determination of relevant EN code Masonry unit EN code (i) Clay bricks or blocks I.S. EN (ii) Calcium silicate bricks I.S. EN (iii) Concrete brick or I.S. EN blocks or 4 (iv) Manufactured stone I.S. EN (v) Square dressed I.S. EN natural stone Compressive strength of masonry units: Minimum compressive strength requirements for masonry units according to I.S. EN standards are given in Table 2. Clay bricks Should have a thickness of 103 mm, be frost resistant and have 7 N/mm2 strength in accordance with I.S. 91: 1983 Clay Building Bricks. Solid concrete blocks Should have thickness required by par and conform to the requirements of. designation S5 in accordance with I.S. 20: 1987 Concrete Building Blocks Part 1: Normal Density Blocks. Lightweight solid concrete blocks Should have thickness required by par and conform to the requirements of designation B3 in accordance with I.S. 20:1974 Concrete Building Blocks. Hollow concrete blocks Should have thickness required by par and conform to the requirements of designation H3 in accordance with I.S. 20: 1987 Concrete Building Blocks Part 1: Normal Density Blocks. Other masonry units Should have strength and masonry thickness equivalent to those units listed above. Lintels Lintels should be designed for the loads and spans occurring where they are employed and should be installed strictly in accordance with the manufacturers instructions. Pre-stressed concrete lintels should be manufactured in accordance with I.S. EN I.S. 240: Mortar Mortar should be: Should conform to the requirements of (a) (i) Strength class M4 according to I.S. EN designation (iii) of I.S. 406: 1987 (nominally a mixture of Portland cement lime and fine aggregate) (b) (ii) 1:1:6 CEM I, lime and fine aggregate measured by volume of dry materials, or of equivalent or greater strength and durability to the specification in (a) above. Wall ties Wall ties should comply with I.S. EN and should be material references 1 or 3 in I.S. EN 845 Table A1 austenitic stainless steel. Wall ties should be selected in accordance with Table NA.1 of I.S. EN I.S. 268: 1987 Metal Wall Ties for Masonry Walls. 11

18 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Table 2 Declared compressive strength for masonry units complying with I.S. EN to 5 (N/mm 2 ) Masonry unit Notes: Clay masonry units to I.S. EN Calcium silicate masonry units to I.S. EN X Aggregate concrete masonry units to I.S. EN Group 1 Group 2 Group 1 Group 2 Group 1 Group 2 Brick Autoclaved aerated concrete masonry units to I.S. EN Manufactured stone masonry units to I.S. EN Block 5.0* 8.0* 5.0* 8.0* 8.9* 4.7* 2.9 # (4.0*) 8.9* 1. Table 2 applies to Group 1 and Group 2 masonry units as defined in I.S. EN Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks) 3. Group 2 masonry units have formed void greater than 25%, but not more than 55% 4. Compressive strengths of masonry units should be derived according to I.S. EN For the EN 771 series of standards for masonry units the values of declared strengths (N/mm2) given in this table are mean values unless other stated by * symbol 6. Brick: a masonry unit having a work size not exceeding mm in length or mm in height 7. Block: a masonry unit exceeding either the limiting work size of a brick and with a minimum height of Legend: 190 mm. For blocks with smaller heights, excluding cuts or make up units, the strength requirements are as for brick except solid external walls where blocks should have a compressive strength at least equal to that shown for block for an inner leaf cavity wall in the same position. * These values are normalised compressive strengths # These values are dry strengths to I.S. EN Maximum Loads Vertical loads (actions) The design considerations given in this section are intended to be adequate for the vertical imposed loads variable actions given in Table 3 should not exceed the following: Table 3 Variable actions Element Variable actions kn/m 2 Roof Floors 1.50 Ceilings Wind actions The maximum allowable height of building which should be adequate for the various site exposure conditions and wind speed should be derived by following the procedure set out in Diagram 1 using the map of wind speeds for Ireland (Figure 1a), orographic zone diagrams (Figure 1b) and Tables 4 and 5. The maximum allowable height of a building (to X fall within the scope of Part 3) can be obtained from Table 6 and correlates to various site exposure conditions and wind speeds. This procedure is based on I.S. EN Where more exposed terrain is involved or where there is reason to believe that higher wind speeds may be appropriate e.g. funneling effects, a separate design check in accordance with I.S. EN should be carried out. Part 3 of this Technical Guidance Document is not applicable if the dynamic design wind pressure/ suction determined in this manner exceeds 1.2 kn/m 2. Diagram 1 shows Ireland divided into three wind zones, A, B and C. The divisions between the zones relate roughly to the 44 m/s and 47 m/s gust speed contours of the map 12

19 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings issued by Met Eireann. The design wind speed (Vs) determined in accordance with CP3: Chapter V: Part 2:1972 as amended in 1986 should not exceed 44 m/s. This condition will normally be satisfied if the building site is located in: Zone A: On normal or slightly sloping sites in any terrain. Zone B: On normal or slightly sloping sites in open country side with scattered windbreaks or in country with many windbreaks or in towns or cities. Zone C: In country with many windbreaks or in towns or cities. Note: For more detailed guidance on these terrains, see CP3: Chapter V: Part 2: Section 5.5. Where more exposed terrain is involved or where there is reason to believe that design wind speeds in excess of 44 m/s may be appropriate, a separate design check in accordance with CP3: Chapter V: Part 2 should be carried out using the wind speeds in Diagram 15 of this Technical Guidance Document. Part 3 of this Technical Guidance Document is not applicable if the design wind speed determined in this manner exceeds 44 m/s. 13

20 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 1 Procedure for determining maximum building heights within the scope of Sub section 1 Part 3 (Par ) 14

21 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings (See Figure 1b) Table 4 Orographic factor O for areas of significant orography Terrain type and average slope of whole hillside, ridge, cliff or Factor O (i) escarpment Zone 1 Zone 2 Zone 3 Nominally flat terrain, average slope ψ 1: Moderately steep terrain, average slope ψ >1:20 but 1: Steep terrain, average slope ψ > 1/5 but 1:3.3 (ii) Notes: (i) The orography factor, accounts for the increase of mean wind speed over isolated hills and escarpments. Outside of the above zones Factor O = 1.0. (i) Average slopes ψ >1:3.3 are outside the scope of this guidance, refer to I.S. EN (See Note below) Table 5 Altitude factor A Site altitude above mean sea level (m) Factor A Note: Where there is significant orography and the site is located within the shaded zone in Figure 1b, then the altitude for determining Factor A may be take as the altitude of the upwind base of the orographic feature. 15

22 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Table 6 Maximum allowable building heights (m) within scope of Sub Section 1 Part 3 S factor Country sites 3 Town sites 4 Distance to sea (see note 2) (see note 2) Distance to sea <2 km 2 20 km >20 km <2 km 2 20 km >20 km > Notes: 1. For sites on the outskirts of towns or not surrounded by other buildings, use the values for country sites; 2. Where a site is located within 1km to an inland area of water which extends more than 1km in area, the distance to the coast should be taken from the water s edge. 3. Country Terrain includes: (i) Area with low vegetation such as grass and isolated obstacles (trees, buildings) with separations of at least 20 obstacle heights. (ii) Lakes or area with negligible vegetation and without obstacles. 4. Town Terrain means: (i) Area in which at least 15 % of the surface is covered with buildings and their average height exceeds 15 m (ii) Area with regular cover of vegetation or buildings or with isolated obstacles with separations of maximum 20 obstacle heights (such as villages, suburban terrain, permanent forest) 16

23 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Retained earth Differences in level of ground or other solid construction between one side of the wall and the other must be less than four times the thickness of the wall. Limitations on building geometry Residential buildings (see Diagram 2) (a) (b) (c) No part of any wall or roof should be more than 10 m above the lowest adjacent ground level. The width of the building should not be less than half the height of the building. The width of a wing should not be less than half the height of the wing when the projection P exceeds twice the width W Floors should be as described below: (a) Ground floors - Timber floors or ground supported concrete floors or suspended concrete floors of maximum span 5 m. (b) Upper floors - Traditional timber floors of maximum span 5 m The floor to floor and ceiling to ceiling heights should not exceed 2.7 m The roof span should not exceed 12 m. Lateral support and end restraint The ends of every load-bearing wall should be bonded or otherwise securely tied throughout their full height to a buttressing wall pier or chimney. The maximum length of wall between vertical supports should not exceed 9 m. Longer walls should be provided with intermediate support, dividing the wall into distinct lengths, by buttressing walls, piers or chimneys, which provide support throughout the full height of the wall. 17

24 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 2 Size and proportion of buildings (Par ) Buttressing The thickness of the buttressing should not be less than 100 mm. Diagram 3 gives details of the limiting dimensions of openings and recesses in walls, including buttressing walls Piers in solid walls should be not less than 190 mm in width and not less than 490 mm thick. Piers in hollow block walls should be not less than 190 mm in width and not less than 590 mm thick. Chimneys should be not less than 490 mm thick and be composed of units not less than 100 mm thick (see Diagram 4). 18

25 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 3 Sizes of openings and recesses (Par ) Internal buttressing to walls in upper floors may be provided by stud partitions not less than 1200 mm long constructed from 35 mm x 75 mm kiln dried timber with studs at not more than 400 mm centres and two rows of noggings. The end stud of the partition should be fixed to the wall using drilled screw fixings at the top and at each of the noggings Notwithstanding the rules in pars to , a supported wall may contain an unbuttressed section adjoining an opening as shown in Diagram 5 where - Diagram 4 Piers and chimneys (Par ) (a) (b) (c) the opening is in the ground storey of an external buttressing wall, the opening does not exceed 2.4 m in height, the supported wall is restrained at first floor level or, where the building is a single storey building, at roof level, 19

26 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings (d) the supported wall is properly bonded to the buttressing wall below the ground floor level, (c) Vertical chases should not be deeper than 1/3 of the thickness of the leaf. (e) (f) (g) (h) the supported wall is bonded to the buttressing wall above the opening by a beam or lintel spanning the opening in the buttressing wall, the buttressing wall is properly bonded to a storey height wall, pier or chimney at the opposite side of the opening to the supported wall, the supported wall is properly bonded to a storey height wall not more than 5.5 m from its unbuttressed section, the beam or lintel described in (e) above is provided at each end with a bearing length of 400 mm or is supported on a padstone having a length of 400 mm. Openings and Chases in Walls The number, size and position of openings should not impair the stability of a wall or the lateral support provided by a buttressing wall to a supported wall. Construction over openings and recesses should be adequately supported and the ends of lintels and beams should be provided with adequate bearing. All window and door lintels should have a minimum bearing length of 150 mm. In certain circumstances e.g. beam bearings, it may be necessary to provide padstones or longer bearings The maximum length of an opening or thickness-reducing recess in any wall should not exceed 3 m. Other dimensional criteria are given in Diagram 3 (see also par ) Openings and thickness-reducing recesses in walls should not exceed 2.4 m in height (see also par ) Dimensional criteria for chases - (a) (b) Chases should not impair the stability of the wall. Chases are not allowed when using hollow blocks. Horizontal chases should not be deeper than 1/6 of the thickness of the leaf. 20

27 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 5 Unbutressed wall sections (Par ) 21

28 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings x Diagram 5 Unbutressed wall sections (Par ) 22

29 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Interaction of elements A wall in each storey of a building should extend to the full height of that storey and have horizontal lateral supports to restrict movement at right angles to its plane Floors and roofs should: (a) (b) act to transfer lateral forces from walls to buttressing walls, piers or chimneys, and be secured to the supported wall by connections specified in pars and Walls should be strapped to floors at first floor level at intervals not exceeding 2000 mm as shown in Diagram 6 (a) and (b) by. 30 x 5 mm galvanised mild steel or stainless steel tension straps which have a minimum 30 mm x 5 mm section conforming to I.S. EN For corrosion resistance purposes, the tension straps should be material reference 14, 16.1 or 16.2 (galvanised steel) or other more resistant specifications including reference 1 or 3 (austenitic stainless steel). The declared tensile strength of tension straps should not be less than 8kN. Straps need not be provided - (a) (b) (c) in the longitudinal direction of joists, if the joists are at not more than 800 mm centres and have at least (i) (ii) 90 mm bearing on the supported walls, or 75 mm bearing on a timber wall plate at each end, in the longitudinal direction of joists where the joists are carried on the supported wall by joist hangers in accordance with I.S. EN of the restraint type described in I.S. 325 and shown in Diagram 6 (c), at not more than 800 mm centres, where floors are at or about the same level on each side of a supported wall as shown in Diagram 6 (d) and contact between floors and wall is either continuous or at intervals not exceeding 2000 mm. Where contact is intermittent, the point of contact should be in line or nearly in line on plan Gable walls should be strapped to roofs as shown in Diagrams 7 (a) and (b) by 30 x 5 mm tension straps as described in galvanised mild steel straps which have a minimum 30 mm x 5 mm section. Vertical strapping at least 1m in length should be provided at eaves level at intervals not exceeding 2000 mm as shown in Diagram 7 (c). Additional vertical straps may be necessary in the following conditions and a separate design check should be carried out to calculate uplift in accordance with I.S. EN These conditions include where the roof: (a) (b) (c) has a pitch of less than 15, and/or is in wind zone C. has a site wind speed equal to or greater than 26 m/s (with reference to Figure 1a of Diagram 1), and/or where the building is located in exposed terrain and there is reason to believe that higher wind speeds may be appropriate Where an opening in a floor or roof, such as that required for a stairway (Diagram 8), adjoins a supported wall and interrupts the continuity of lateral support, the following conditions should be satisfied: (a) (b) (c) the length of opening should not exceed 3000 mm measured parallel to the supported wall, and where a connection is provided by means other than by anchor, this should be provided throughout the length of each portion of the wall situated on each side of the opening, and where connection is provided by mild steel or stainless steel anchors or by packs, these should be spaced closer 23

30 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings than 2000 mm on each side of the opening to provide the same number as if there were no opening, and (d) there should be no other interruption of lateral support Wall ties should be provided in cavity walls and should comply with I.S. EN In conditions of severe exposure, austenitic stainless steel or suitable nonferrous ties should be used. The minimum quantity of ties provided should be 2.5 per square metre in accordance with I.S. EN and I.S. EN for cavities of 50mm - 75 mm width and 3 per square metre for cavities of 75 mm mm. Extra wall ties are required at the jambs of openings and movement joints as shown in Diagram 9 (for definitions of severe exposure and for use of ties in other cavity widths, see I.S : 2011) (This standard is due to be published shortly as Non Contradictory Complimentary Information to the Eurocode 6) 24

31 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 6 Lateral support by floors (Par ) 25

32 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 7 Lateral support at roof level (Par ) 26

33 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 8 Interruption of lateral support (Par ) 27

34 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Diagram 9 Spacing of wall ties (Par ) 28

35 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Part 4 - Proportions for masonry chimneys above the roof surface Height to width relationship Where a chimney is not supported by adequate ties or otherwise made secure, its height (H), measured from the level of the highest point of intersection with the roof surface, gutter or other part of the building and including any flue pot or terminal, should not be more than X times multiplied by W, provided the density of the masonry is greater than 2000 kg/m 3, where with reference to Diagram 1, Figure 1a): X = 4.5 in zone A where the site wind speed 25m/s X = 4.0 in zone B where the site wind speed 26m/s but >25m/s X = 3.5 in zone C where the site wind speed > 26m/s W is the least horizontal dimension of the chimney measured at the same point of intersection (see Diagram 10). Notes: The zones are described in Diagram 1. The proportions given in this paragraph are intended for general application. More slender chimneys may be built if they can be shown by calculation to be stable in the particular wind environment of the building. Diagram 10 Proportions for masonry chimneys (Par ) Part 5 - Strip foundations of plain concrete Conditions relating to the subsoil There should not be - (a) (b) made ground or wide variation in type of subsoil within the loaded area, or weaker type of soil at such a depth below the soil on which the foundation rests as could impair the stability of the structure. Design provisions The following design provisions relate to foundations - (a) (b) (c) the foundations should be situated centrally under the wall; strip foundations should have minimum widths in accordance with par ; concrete should be composed of a cement (Type CEM I or CEM II/A L/LL, CEM II/A-V, or CEM II/A-S) to I.S. EN 197-1:2001 +A3: 2007 or a cement with up to 70% GGBS (to I.S. EN : 2006) or with up to 35% PFA (to. I.S. EN 450-1: A1:2007) and fine and coarse aggregate conforming to I.S. 5: 1990 I.S. EN 12620: S.R. 16:2004 and be one of the following grades - (i) in accordance with Table 3.4 of I.S NA.5 of I.S. EN 206-1:2002 for reinforced foundations, or (ii) Class C12/15 (characteristic 28 day strength of 15 N/mm 2 ) with minimum cement content 200 kg/m 3 and maximum water cement ratio 0.85 for plain concrete unreinforced foundations in nonaggressive ground conditions (when volumetric mixing is required for small projects, a 1:7 cement/aggregate mix may be used), (d) minimum thickness T of concrete foundation should be 200 mm or P, whichever is the greater, where P is 29

36 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings (e) derived using Table 7 (see Diagram 11); foundations stepped on elevation should overlap by Diagram 12 Elevation of stepped foundation (Par ) (i) (ii) (iii) twice the height of the step, or the thickness of the foundation, or 300 mm, (f) (g) whichever is greater (see Diagram 12); steps in foundations should not be of greater height than twice the thickness of the foundation and should course with walling material (see Diagram 12); foundation of piers, buttresses and chimneys should project as indicated in Diagram 13 and the projection X should never be less than P.. Diagram 13 Piers and chimneys (Par ) Diagram 11 Foundation dimensions (Par ) Minimum width of strip foundations Providing the previous conditions relating to the subsoil (par ) and design provisions relating to the foundations (par ) are observed and the type and condition of subsoil is known and loading at the base of the wall is within acceptable limits, the recommended widths of foundations given in Table 7 may be used 30

37 Sub-section 1 - Sizes for certain structural elements for houses and other small buildings Table 7 Minimum width of strip foundations Type of subsoil I rock II gravel sand III clay sandy clay boulder clay IV clay sandy clay boulder clay V sand silty sand clayey sand boulder clay VI silt clay sandy clay silty clay VII silt clay sandy clay silty clay Condition of subsoil not inferior to sandstone, limestone or firm chalk compact compact stiff stiff stiff firm firm firm loose loose loose loose soft soft soft soft very soft very soft very soft very soft Field test applicable requires at least a pneumatic or other mechanically operated pick for excavation requires pick for excavation. A wooden peg 50 mm square in cross section hard to drive beyond 150 mm cannot be moulded with the fingers and requires a pick or pneumatic or other mechanically operated spade for its removal can be moulded by substantial pressure with the fingers and can be excavated with a spade can be excavated with a spade. A wooden peg 50 mm square in cross section can be easily driven fairly easily moulded in the fingers and readily excavated natural sample in winter conditions exudes between fingers when squeezed in fist Total load of load-bearing walling not more than (kn/linear metre) Minimum width of strip foundation (mm) In each case the width (wt) of wall plus 150 mm Note: Where there is any doubt as to the condition of the subsoil, and always in the case of subsoil types V, VI and VII, an appropriate site investigation, on which the foundation design can be based, is essential. Note: In no case should the width of the foundation be less than the total width of the wall plus 75 mm on each side. 31

38 Sub-section 2 - Design and construction of all building types codes, standards and references Sub-section 2 Design and construction of all building types - codes, standards and references Introduction The following codes, standards and references are appropriate for all buildings and may be used to meet Requirements A1 and A2 provided that; (a) (b) the design and construction of a structure is in accordance with the relevant recommendations of the codes, standards and references, and where alternative codes and standards have been listed, the whole of the design for the same material should normally be based on one of the codes only. Any reference to the European Standards for Structure (Structural Eurocodes) must be taken to include reference to the relevant Irish National Annex. The reliability of designs carried out in accordance with the Eurocodes is based on a number of assumptions set out in I.S. EN 1990: 2002 that include: the choice of the structural system and the design of the structure is made by appropriately qualified and experienced personnel; the design and construction is carried out by personnel having the appropriate skill and experience; adequate supervision and quality control is provided during execution of the work; the construction materials and products are used as specified in I.S. EN 1990 or in I.S. EN 1991 to I.S. EN 1999 or in the relevant execution standards, or reference material or product specifications; the structure will be adequately maintained; and the structure will be used in accordance with the design assumptions. Where reference is made to an Irish or British Code of Practice it should be noted that Eurocodes covering the same topic which have been issued by CEN as provisional Euronorms may be used subject to the requirements of the Irish National Application Document for the relevant Eurocode. Codes, standards and references Loading BS 6399 : Part 1 (For dead and imposed loads, other than imposed roof loads) BS 6399: Part 2 (For wind loads and using the wind speed map in diagram 15 A) BS 6399 : Part 3 (For imposed roof loads and using the snow load map in Diagram 14) CP 3: Chapter V: Part 2: 1972 (For wind loads (although in no case shall the factor S3 be taken at less than l) and using the appropriate basic wind speed shown on the map in Diagram 15) supplemented, as appropriate, by BRE Digest 346. Note: Exceptionally, where the actual load is greater than the BS 6399: Part 1: 1984 design loads, the actual load should be used, having regard to par of this Technical Guidance Document. Eurocode 0: Basis of structural design I.S. EN 1990: 2002 Eurocode 1: Actions on Structures I.S. EN : 2002 I.S. EN : 2002 I.S. EN : 2003 (Diagram 14 is an extract from this part s National Annex) I.S. EN : 2005 I.S. EN : 2003 I.S. EN : 2005 I.S. EN : 2006 I.S. EN : 2003 I.S. EN : 2006 I.S. EN : 2006 Structural work of reinforced, prestressed or plain concrete I.S. 326: 1995 I.S. EN 206-1:2002 Eurocode 2: Design of Concrete Structures I.S. EN :

39 Sub-section 2 - Design and construction of all building types codes, standards and references I.S. EN : 2005 I.S.EN : 2006 BS 5268: Part 2: 1991 I.S. 440:2009 Structural work of steel BS 5950: Part 1: 1990 BS 5950: Part 2: 1992 BS 5950: Part 4: 1994 BS 5950: Part 5: 1987 Eurocode 3: Design of Steel Structures I.S. EN : 2005 I.S. EN : 2005 I.S. EN : 2006 I.S. EN : 2006 I.S. EN : 2006 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2005 I.S. EN : 2005 I.S. EN : 2005 I.S. EN : 2006 I.S. EN : 2007 I.S. EN : 2006 I.S. EN : 2006 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 Structural work of composite steel and concrete construction BS 5950: Part 3: Section 3.1: 1990 Eurocode 4: Design of Composite Concrete and steel structures I.S. EN : 2005 I.S. EN : 2005 Structural work of timber Eurocode 5: Design of Timber Structures I.S. EN : 2005 I.S. EN : 2005 I.S. 193: 1986 SWiFT 5 (formerly called I.S. 193). This document is currently under preparation and is due to be published as Non Contradictory Complimentary Information to the Eurocodes. SR 11 : 1988 SWiFT 6 (formerly called I.S. 444). This document is currently under preparation and is due to be published as Non Contradictory Complimentary Information to the Eurocodes). Structural work of masonry I.S. 325 Part 1: 1986 Eurocode 6: Design of Masonry Structures I.S. EN : 2005 I.S. EN : 2005 I.S. EN : 2006 I.S. EN : 2006 BS 5628: Part 2: 1985 I.S : Code of Practice for Use of Masonry: Masonry Construction (This standard is under review and is due to be published shortly as Non Contradictory Complimentary Information to the Eurocode 6) Foundations - General BS 8004: 1986 Eurocode 7: Geotechnical Design I.S. EN : 2005 I.S. EN : 2007 Structural work of aluminium CP 118: 1969 using one of the principal or supplementary aluminium alloys designated in Section 1.1 of that code, and for the purposes of Section 5.3 of that code, the structure should be classified as a safe-life structure. BS 8118: Part 1: 1991, for the purposes of Section 7 of that standard, the structure should be designed to provide a safe life. BS 8118: Part 2: 1991 Eurocode 9: Design of Aluminium Structures I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 Structural work of glass BS 6262: 1982 BS :2005 BS :2005 BS :2005 BS : 2005 BS : 2005 BS : 2005 BS :

40 Sub-section 2 - Design and construction of all building types codes, standards and references Appraisal of existing buildings Appraisal of existing structures 2 nd edition Institution of Structural Engineers Building Research Establishment Digest 366: Structural appraisal of existing buildings for change of use 1991 Structural renovation of traditional buildings, Report 111. Construction Industry Research and Information Association (1994 reprint with amendments) 34

41 Sub-section 2 - Design and construction of all building types codes, standards and references Diagram 14 Basic snow load at 100m Ordinance Datum (Refer to I.S. EN ) NOTE 1 The values shown on the map above should be used for all site altitudes 100 m O.D. NOTE 2 For sites with an altitude (A) above 100 m O.D., a correction figure of (A-100) / 500 kn/m 2 should be added to the values shown on the map. 35

42 Sub-section 3 - Recovering of existing roof structures and structural safety of external wall cladding Sub-section 3 Recovering of Existing Roof Structures and Structural Safety of External Wall Cladding Recovering of existing roof structures Where new roof coverings would impose higher loads on the roof structure or where the new material would be lighter than the original material, strengthening measures may be required. The following procedure is recommended: (a) (b) (c) (d) (e) arrange for a thorough structural survey of the existing roof structure and the vertical restraints, check the dry mass per unit area of the proposed roof covering and compare it with that of the existing roof covering, make allowance for the increase in load due to water absorption, e.g. 0.3% for oven dry slates and up to 10.5% for clay plain tiles and concrete tiles, check if the roof structure is capable of sustaining the increased load or if the vertical restraints provided to the roof structure are adequate for the wind uplift (the uplift may result due to the use of lighter roofing material and/or provision of new underlay), provide appropriate strengthening measures such as: (i) (ii) (iii) replacement of defective members and vertical restraints, additional structural members such as trusses, rafters, bracings, or purlins, etc., required to sustain increased loading, restraining straps, additional ties and fixings to the walls to resist wind uplift. Structural safety of external wall cladding General The remainder of this sub-section includes guidance for the design and construction of external wall cladding. The guidance is applicable to cladding which by reason of weight or height would present a hazard if it became detached from the building. For the purposes of this section, cladding is deemed to include glazed curtain walling but not windows These provisions are not intended to provide guidance concerning the weather resistance of wall cladding which is included in Technical Guidance Document C, Site preparation and resistance to moisture, or guidance on resistance to fire which is included in Technical Guidance Document B, Fire Safety Wall cladding should be capable of safely sustaining and transmitting to the supporting structure of the building all the loadings liable to act on it. dead, imposed and wind loads Wall cladding should be securely fixed to and supported by the supporting structure of the building. This should comprise both vertical support and hold back restraint Provision should be made, where necessary, to accommodate differential movement of the cladding and the supporting structure of the building The cladding and its fixings (including any support components) should be of durable materials, the anticipated life of the fixings being not less than that of the cladding. Where the fixings are not readily accessible for inspection and maintenance, particular care will be required in the choice of materials and standard of workmanship to be achieved (see Technical Guidance Document D). Fixings should be corrosion resistant and of a material type appropriate to the local environment. Technical approach Loading Wind loading on the wall cladding should be derived from I.S. EN however in no case should the seasonal factor (c season ) be taken as less than 1.0. CP 3: Chapter V: Part 2: 1972, supplemented, as appropriate, by 36

43 Sub-section 3 - Recovering of existing roof structures and structural safety of external wall cladding BRE Digest 346, using Class A building size for determining ground roughness factor S2. In no case should the factor S3 be taken as less than 1. Due consideration should be given to local increases in wind suction arising from funneling of wind through gaps between buildings. Forces imposed on wall cladding by ladders or access cradles for the purpose of maintenance should be derived from a consideration of the equipment likely to be used Where the wall cladding is required to support other fixtures, e.g. handrails, and fittings e.g. antennae, signboards, etc., full account should be taken of the loads and forces arising from such fixtures and fittings Where the wall cladding is required to function as pedestrian guarding to a stairway, ramp, vertical drop of 600 mm or greater or as a vehicle barrier, then account should be taken of the additional imposed loading, as stipulated in Technical Guidance Document K, Stairways, Ladders, Ramps and Guards Where the wall cladding is required to safely withstand the lateral pressures from crowds, an appropriate design loading is given in I.S. EN For sports stadia, imposed loading should be that stipulated in Table 3 of BS 6180, where the wall cladding is required to function as pedestrian guarding Fixings The selection of fixings for supporting cladding should be determined from consideration of the proven performance of the fixing and the risks associated with the particular application. In this regard applications should be designated as being either non-redundant (where the failure of a single fixing could lead to the detachment of the cladding) or redundant (where failure or excessive movement of one fixing results in load sharing by adjacent fixings) and the required reliability of the fixing determined accordingly. Attention is drawn to the availability of anchors with an ETA (European Technical Approval) gained in accordance with the requirements of ETAG 001 Guidelines for European Technical Approval Metal Anchors for use in Concrete Parts 1-5, which cover both redundant and non-redundant applications and Part 6 which covers Anchors for multiple use in non-structural applications and which can effectively be regarded as covering redundant use. The definition of multiple use is contained in the annex to the ETAG Part 6 and is framed in such a way that all applications can be validated as to whether or not they conform to this category without calculation. All ETAG parts may be downloaded in English from For design purposes, the strength of a fixing should be derived from tests using materials representative of the base material of the structure into which the fixing is to be anchored. Account should also be taken of any inherent weaknesses in the base material of the structure that may affect the strength of the fixing, e.g. cracks due to shrinkage or flexure or voids in masonry construction. The design loads will generally be available from the manufacturer s test data determined from a European Technical approval (ETA). ETAs are available which cover use either in both cracked and non-cracked concrete or in cracked concrete only. Those which cover both cracked and non-cracked allow higher loads for use in non-cracked than in cracked concrete. Guidance on how to determine whether a particular concrete section may be regarded as cracked or non-cracked without reverting to stress calculations is contained in Use of anchors with European Technical Approvals. UK Guidance distinction between cracked and non-cracked concrete Further guidance on fixings Additional guidance on fixings is given in the following documents: ETAG No Guidelines for European Technical Approvals of Metal Anchors for use in Concrete, European Organisation for Technical Approvals (EOTA) 37

44 Sub-section 3 - Recovering of existing roof structures and structural safety of external wall cladding Code of practice for the design and installation of anchors Health and Safety Authority For the purpose of such tests the following Standards and Reference may be used: BS :1994 BS :1986 UEAtc Technical Guide on Anchors for use in cracked and non-cracked concrete. MOAT No 49. BS 5427: Where expanding bolt type fixings are provided, their safe working shear and tensile loads should not exceed the lower of the following values - (a) A factor of safety of 3 applied to: the mean shear or tensile failure test load less 3 times the standard deviation derived from the tests. (b) The mean of the loads which cause a displacement of 0.1 mm under direct tension and 1.0 mm under direct shear. The design of certain resin bonded fixings should take account of their rapid loss of strength at temperatures above 50 C. The component parts of mechanical fixings should be lockable or be otherwise mechanically fixed together to prevent unintended slippage between the parts Movement - Guidance is given in BS 8200: 1985 and I.S. 325: Part 2: 1995 (under revision and due to be re-published as Non Contradictory Complimentary Information to Eurocode 6) on the means of providing for the differential movement of the wall cladding and the supporting structure of the building. Codes and Standards The following Codes and Standards may be used in designing wall cladding: General BS 8200: 1985 The Institution of Structural Engineers Report on Aspects of Cladding dated 1995 Loading I.S. EN : 2005 CP 3: Chapter V: Part 2: 1972 Wind loads supplemented as appropriate by BRE Digest 346, (although in no case shall the factor S3 be taken as less than 1). Stone and concrete cladding I.S. 326: 1995 BS 8297: BS 8298: 1994 Masonry cladding I.S. 325: Part 1: 1986 I.S. 325: Part 2: 1995 (under revision, due to be re-published shortly as Non Contradictory Complimentary Information to Eurocode 6) BS 5628: Part 2: 1995 I.S. EN : 2005 I.S. EN : 2005 I.S. EN : 2006 I.S. EN : 2006 Steel cladding BS 5950: Part 1: 1990 BS 5950: Part 5: 1987 I.S. EN : 2005 I.S. EN : 2006 I.S. EN : 2006 I.S. EN : 2007 I.S. EN : 2005 I.S. EN : 2005 Aluminium cladding CP 118: 1969 BS 8118: Part 1: 1991 I.S. EN : 2007 I.S. EN : 2007 I.S. EN : 2007 Timber cladding BS 5268: Part 2: 1991 I.S. EN : 2005 I.S. 440:2009 External Timber Cladding 2 nd Edition 2007, TRADA Profiled sheet cladding BS : Glass cladding BS : BS :

45 Sub-section 3 - Recovering of existing roof structures and structural safety of external wall cladding Note: The use of large panels of glass in cladding of walls and roofs where the cladding is not divided into small areas by load-bearing framing requires special consideration. Guidance is given in the following document: The Institution of Structural Engineers Report on Structural use of glass in buildings. 39

46 Section 2 Disproportionate collapse Section 2 Disproportionate collapse Disproportionate collapse A3 (1) A multi-storey building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that in the event of an accident the structure will not be damaged to an extent disproportionate to the cause of the damage. (2) For the purposes of sub-paragraph (1), where a building is rendered structurally discontinuous by a vertical joint, the building on each side of the joint may be treated as a separate building whether or not such joint passes through the substructure. Codes and standards 2.1 The following Codes and Standards may be used in designing to meet the Requirement A3 provided the recommendations on ties and the recommendations on the effect of misuse or accident are followed. Structural work of reinforced, prestressed or plain concrete I.S. 326 : 1995 Structural work of steel BS 5950: Part 1: 1990 (The accidental loading referred to in Clause should be chosen having particular regard to the importance of the key element and the consequences of failure, and the key element should always be capable of withstanding a load of at least 34 kn/m2 applied from any direction). Structural work of masonry I.S. 325 : Part 1: 1986 I.S. 325 : Part 2: 1995 Introduction 2.1 The Requirement A3 will be met by adopting the following approach for ensuring that the building is sufficiently robust to sustain a limited extent of damage or failure, depending on the class of the building, without collapse. All buildings must be designed to accommodate unforeseen or accidental actions in such a way as to prevent the extent of any resulting collapse being disproportionate to the cause of the collapse. Buildings should be designed so that they are robust which is defined in I.S EN as the ability of a structure to withstand events like fire, explosions, impact or the consequences of human error without being damaged to an extent disproportionate to the original cause. Disproportionate collapse 2.2 A building which is susceptible to disproportionate collapse is one where the effects of accidents and, in particular, situations where damage to small areas of a structure or failure of single elements could lead to collapse of major parts of the structure. Buildings should be provided with a level of robustness by adopting the principles of risk analysis, categorising buildings, taking into account both the risk of the hazard and its consequences and providing additional measures commensurate to the level of risk and consequences of such collapse of the building. The risk level and accidental actions that should be considered when undertaking the structural design of a building for disproportionate collapse should be in accordance with the recommendations of I.S. EN or the method set out below. Other additional material specific requirements may be outlined in I.S. EN to I.S. EN and I.S. EN Any reference to European Standards for Structure (Structural Eurocodes) in this 40

47 Section 2 Disproportionate collapse section must be taken to include the relevant Irish National Annex. To ensure that buildings are designed and constructed to sustain a limited extent of damage or failure without a disproportionate level of collapse from an unspecified cause, the following procedure should be followed: Step 1 - Determine the building consequence class (refer to Table 8); Step 2 - Assess additional measures; Step 3 - Design and construct additional measures. Determine building consequence class 2.3 The issues to be considered with respect to assessing the consequence class (risk group) of a building are its occupancy level, use, the number of storeys and floor areas. The risk of an extreme event such as an explosion or other incident occurring would not be decreased simply by providing these measures and there is no certainty that demolition or building alteration would be carried out in accordance with good practice but the consequences of such an incident occurring would be considerably reduced. Assess additional measures 2.4 The additional measures which should be provided vary extensively according to building type and use and the actual measures should be designed in accordance with the relevant sections of the design codes. For example, high rise hotels or apartment buildings or assembly buildings or grandstands require a different level of robustness than low rise buildings or storage buildings. The additional measures which should be applied to buildings of the risk groups derived from the above table are set out below: For Class 1 building Provided the building has been designed and constructed in accordance with the rules given in this Technical Guidance Document for meeting compliance with A1 and A2 in normal use, no additional measures are likely to be necessary. For Class 2A building Provide effective horizontal ties, or effective anchorage of suspended floors to walls, for framed and load-bearing wall construction. For Class 2B building Provide effective horizontal ties for framed and load-bearing wall construction, together with effective vertical ties, in all supporting columns and walls. Alternatively, check that upon the notional removal of each supporting column and each beam supporting one or more columns, or any nominal length of load-bearing wall (one at a time in each storey of the building) the building should remain stable and that the area of floor at any storey at risk of collapse should be not more than 15% of the floor area of that storey or100 m 2, whichever is smaller and does not extend further than the immediate adjacent storeys (see Diagram 15) Where the notional removal of such columns and lengths of walls would result in an extent of damage in excess of the above limit, then such elements should be designed as key elements. For Class 3 buildings A systematic risk assessment of the building should be carried out; taking into account all the normal hazards that can be foreseen as far as possible together with any abnormal hazards. Critical situations for design should be selected that reflect the conditions that can be foreseen as far as possible during the life of the building. The structural form and concept and any protective measures should then be chosen and the detailed design of the structure and its elements undertaken in accordance with the recommendations in the codes and standards in clause

48 Section 2 Disproportionate collapse Design and construct additional measures 2.5 The structural design and construction should take account of the additional measures including horizontal and vertical ties where appropriate and checking the integrity of the building following the notional removal of vertical members and the design of key elements, should be carried out in accordance with the design recommendations contained in Annex A of I.S. EN and any other specific requirements in I.S. EN to I.S. EN and I.S. EN and their National Annexes. 2.6 Definitions Key element A key element is a structural member upon which the stability of the remainder of the structure depends and should be capable of sustaining an accidental design loading of 34 kn/m 2 applied in the horizontal and vertical directions (in one direction at a time) to the member and any attached components such as cladding, having regard for the ultimate strength of such components and their connections. Such accidental design loading should be assumed to act simultaneously with 1/3 of all normal characteristic loading. - in the case of an internal masonry wall, or timber or steel stud wall, a length no exceeding 2.25H where H is the storey height in metres Additional information 2.2 Structural failure of any member not designed as a protected key element or member in any one storey should not result in failure of the structure beyond the immediately adjacent storeys or beyond an area within those storeys of: (a) 70 m2, or (b) 15 per cent of the area of the storey, whichever is less. Protected key elements or members are single structural elements on which large parts of the structure rely (i.e. supporting a floor or roof area of more than 70 m2 or 15 per cent of the area of the storey, whichever is less). Their design, which should take their importance into account, and the least loadings they have to withstand are described in the Codes and Standards listed above. Load-bearing construction For the purposes of this Guidance the term load-bearing wall construction includes masonry cross-wall construction and walls comprising of close centred timber or lightweight steel section studs Nominal length of load-bearing wall The nominal length of load-bearing wall construction referred to for Class 2b buildings should be taken as follows: - in the case of a reinforced concrete wall, the distance between lateral supports subject to a maximum length not exceeding 2.25H. - in the case of an external masonry wall, or timber or steel stud wall, the length measured between vertical lateral supports 42

49 Section 2 Disproportionate collapse Table 8 Building classes (Par 2.2) Consequence Building type and occupancy Class Single occupancy houses not exceeding 4 storeys. 1 Agricultural buildings; 2a Lower Risk Group 2b Upper Risk Group 3 Buildings into which people rarely go, provided no part of the building is closer to another building, or area where people do go, than a distance of 1.5 times the building height. 5 storey single occupancy houses; Hotels not exceeding 4 storeys; Flats, apartments and other residential buildings not exceeding 4 storeys; Offices not exceeding 4 storeys; Industrial buildings not exceeding 3 storeys; Retailing premises not exceeding 3 storeys of less than 1000 m 2 floor area in each storey; Single storey educational buildings; All buildings not exceeding two storeys to which the public are admitted and which contain floor areas not exceeding 2000 m 2 at each storey. Hotels, flats, apartments and other residential buildings greater than 4 storeys but not exceeding 15 storeys; Educational buildings greater than single storey but not exceeding 15 storeys; Retailing premises greater than 3 storeys but not exceeding 15 storeys; Hospitals not exceeding 3 storeys; Offices greater than 4 storeys but not exceeding 15 storeys; All buildings to which the public are admitted and which contain floor areas exceeding 2000 m 2 but not exceeding 5000 m 2 at each storey; Car parking not exceeding 6 storeys. All buildings defined above as Class 2 Lower and Upper Consequences Class that exceed the limits on area and number of storeys; All buildings to which members of the public are admitted in significant numbers; Stadia accommodating more than spectators; Buildings containing hazardous substances and /or processes NOTE 1 NOTE 2 NOTE 3 For buildings intended for more than one type of use the consequences class should be that relating to the most onerous type In determining the number of storeys basement storeys may be excluded provided such basement storeys fulfil the requirements of "Consequences Class 2b Upper Risk Group" Table 8 is not exhaustive and can be adjusted 43

50 Section 2 Disproportionate collapse Diagram 15 Area at risk of collapse in the event of an accident (Par 2.4) 44

51 Standards and publications Note: Any reference to European Standards in this section must be taken to include the relevant Irish National Annex. Standards referred to: I.S : 2011 Code of Practice for Use of Masonry : Masonry Construction (This standard is under review and is due to be published shortly as Non Contradictory Complimentary Information to the Eurocode 6) I.S. 440:2009 Timber framed dwellings I.S. EN 197-1: A3:2007 Cement - Part 1: Composition, specifications and conformity criteria for common cements I.S. EN 206-1:2002 Concrete Part 1: Specification, performance, production and conformity I.S. EN 450-1:2005+A1:2007 Fly ash for concrete Part 1: Definitions, specifications and conformity criteria I.S. 5: 1990 Aggregates for Concrete I.S. 20: 1974 Concrete Building Blocks I.S. 91: 1983 Clay Building Bricks I.S. EN 771-1:2003 Specification for masonry units Part 1: Clay masonry units I.S. 190: 1974 Calcium Silicate Building Bricks I.S. EN 771-2:2003 Specification for masonry units Part 2: Calcium silicate masonry units I.S. EN 771-3:2003 Specification for masonry units Part 3: Aggregate concrete masonry units (Dense and lightweight aggregates) I.S. 20: Part 1: 1987 Concrete Building Blocks, Part 1 Normal Density Blocks I.S. 189: 1974 Concrete Building Bricks I.S. EN 771-4:2003 Specification for masonry units Part 3: Autoclaved aerated concrete masonry units I.S. EN 771-5:2004 Specification for masonry units Part 5: Manufactured stone masonry units I.S. EN 771-6:2005 Specification for masonry units Part 6: Natural stone masonry units I.S. EN 845-1:2003+A1:2008 Specification for ancillary components for masonry Part 1: Ties, tension straps, hangers and brackets I.S. 268: 1986 Metal Wall Ties for Masonry Walls I.S. EN 845-2:2003 Specification for ancillary components for masonry Part 2: Lintels I.S. 240: 1980 Precast Prestressed Concrete Units for use in Composite Lintels I.S. EN 845-3:2003+A1:2008 Specification for ancillary components for masonry Part 3: Bed joint reinforcement of steel meshwork I.S. EN 934-2:2009 Admixtures for concrete, mortar and grout Part 2: Concrete admixtures, Definitions, requirements, conformity, marking and labeling I.S. EN 934-3:2009 Admixtures for concrete, mortar and grout Part 3: Admixtures for masonry mortar, Definitions, requirements, conformity and marking and labeling 45

52 Standards and publications I.S. EN 934-5:2007 Admixtures for concrete, mortar and grout Part 5: Admixtures for sprayed concrete, Definitions, requirements, conformity and marking and labelling I.S. EN 998-1:2003 Specification for mortar for masonry Part 1: Rendering and plastering mortar I.S. EN 998-2:2003 Specification for mortar for masonry Part 2: Masonry mortar I.S. EN 1520:2002 Prefabricated reinforced components of lightweight aggregate concrete with open structure I.S. EN :2004 Hot rolled products of structural steels Part 1: General technical delivery conditions I.S. EN 10080:2005 Steel for the reinforcement of concrete weldable reinforcing steel General I.S. EN 12620:2002 Aggregates for concrete I.S. EN :2002 Light weight aggregates - Part 1: Lightweight aggregates for concrete, mortar and grout I.S. EN : 2004 Lightweight aggregates - Part 2: Lightweight aggregates for bituminous mixtures and surface treatments and for unbound and bound applications I.S. EN 13139:2002 Aggregates for mortar I.S. EN 13224:2004+A1:2007 Precast concrete products Ribbed floor elements I.S. EN 13225:2004 Precast concrete products Linear structural elements I.S. EN :2005+A1:2009 Silica fume for concrete - Part 1: Definitions, requirements and conformity criteria I.S. EN :2002 Armourstone Part 1: Specification I.S. EN :2006 Ground granulated blast furnace slag for use in concrete mortar and grout Part 1: Definitions, specifications and conformity criteria S.R. 16:2004 Guidance on the use of I.S. EN 12620:2002 Aggregates for concrete S.R. 18:2006 Guidance on the use of I.S. EN 13139:2002 Aggregates for mortar S.R. 24:2004 Guidance on the use and application of European Test Method - Standards for aggregates BS 1297: 1987 Specification for tongued and grooved softwood flooring BS 4449: A2:2009 Steel for the reinforcement of concrete Weldable reinforcing steel Bar, coil and decoiled product Specification BS 4471: 1987 Specification for sizes of sawn and processed softwood AMD 8901 BS 4482:2005 Steel wire for the reinforcement of concrete products Specification BS 4483:2005 Steel fabric for the reinforcement of concrete Specification 46

53 Standards and publications BS :1994 Structural fixings in concrete and masonry Part 1: Method of test for tensile loading BS :1986 Structural fixings in concrete and masonry Part 2: Method of determination of resistance to loading in shear (AMD 7602) BS 5268: Structural use of timber Part 2: 1991 Code of practice for permissible stress design, materials and workmanship AMD 8597 BS 5268: Structural use of timber Part 6: Code of practice for timber frame walls Section 6.1: 1988 Dwellings not exceeding three storeys AMD 6743 BS 5390: 1976 (1984) Code of practice for stone masonry AMD 4272 BS 5427: 1976 Code of practice for performance and loading criteria for profiled sheeting in building BS :2004 Patent glazing and sloping glazing for buildings Part 1: Code of practice for design and installation of sloping and vertical patent glazing BS :2004 Patent glazing and sloping glazing for buildings Part 2: Code of practice for sloping glazing BS 5628: Code of practice for use of masonry Part 2: 1985 Structural use of reinforced and prestressed masonry BS 5950: Structural use of steelwork in building Part 1: 1990 Code of practice for design in simple and continuous construction: hot rolled sections AMD 6972 BS 5950: Structural use of steelwork in building Part 2: 1992 Specification for materials, fabrication and erection: hot rolled sections AMD 7766 BS 5950: Structural use of steelwork in building Part 3: Design in composite construction Section 3.1: 1990 Code of practice for design of simple and continuous composite beams BS 5950: Structural use of steelwork in building Part 4: 1994 Code of practice for design of composite slabs with profiled steel sheeting BS 5950: Structural use of steelwork in building Part 5: 1987 Code of practice for design of cold formed sections AMD 5957 BS 5950: Structural use of steelwork in building Part 6: 1995 Code of practice for design of light gauge profiled steel sheeting BS 6180: Code of practice for Barriers in and about buildings BS 6262: 1982 Code of practice for glazing for buildings AMD 4063; AMD 4582; AMD 8279 (Partially superseded but remains current) BS :2005 Glazing for buildings Part 1: General methodology for the selection of glazing BS :2005 Glazing for buildings Part 2: Code of practice for energy, light and sound BS :2005 Glazing for buildings Part 3: Code of practice for fire, security and wind loading; BS : Glazing for buildings Part 4: Code of practice for safety related to human impact BS : 2005 Glazing for buildings Part 5: Code of practice for frame design considerations; BS : 2005 Glazing for buildings Part 6: Code of practice for special applications; BS : 2005 Glazing for buildings Part 7: Provision of information. 47

54 Standards and publications BS 6399: Loading for buildings Part 1: 1984 Code of practice for dead and imposed loads AMD 4949; AMD 5881; AMD 6031 BS 6399: Loading for buildings Part 2: Code of Practice for wind loads BS 6399: Design loading for buildings Part 3 : 1988 Code of practice for imposed roof loads AMD 6033 BS 6750: 1986 Specification for modular co-ordination in building BS 8002: 1994 Code of practice for earth retaining structures AMD 8851 BS 8004: 1986 Code of practice for foundations BS 8118: Structural use of aluminium Part 1: 1991 Code of practice for design BS 8118: Structural use of aluminium Part 2: 1991 Specification for materials, workmanship and protection BS 8200: 1985 Code of practice for design of non-loadbearing external vertical enclosures of buildings BS 8219: 2001 Installation of sheet roof and wall coverings Profiled fibre cement Code of practice BS 8298: 1994 Code of practice for design and installation of natural stone cladding and lining CP 3: Chap. V: Part 2: 1972 Wind loads AMD 4952; AMD 5152; AMD 5343; AMD 6028; AMD 7908 CP 118: 1969 The structural use of aluminium AMD 1129 Structural Eurocodes I.S. EN 1990: 2002 Eurocode: Basis of structural design. I.S. EN : 2002 Actions on structures General actions - Densities, self weight and imposed loads for buildings I.S. EN : 2002 Actions on structures - General actions Actions on structures exposed to fire I.S. EN : 2003 Actions on structures General actions - Snow loads I.S. EN : 2005 Actions on structures General actions - Wind actions I.S. EN : 2003 Actions on structures General actions - Thermal actions I.S. EN : 2005 Actions on structures General actions - Actions during execution I.S. EN : 2006 Actions on structures General actions - Accidental actions I.S. EN : 2003 Actions on structures - Traffic loads on bridges I.S. EN : 2006 Actions on structures - Actions induced by cranes and machines I.S. EN : 2006 Actions on structures - Silos and tanks I.S. EN : 2005 Design of concrete structures - General rules and rules for buildings 48

55 Standards and publications I.S. EN : 2005 Design of concrete structures General rules - Structural fire design I.S.EN : 2006 Design of concrete structures - Liquid retaining and containing structures I.S. EN : 2005 Design of steel structures - General rules and rules for buildings I.S. EN : 2005 Design of steel structures General rules - Structural fire design I.S. EN : 2006 Design of steel structures General rules - Supplementary rules for cold formed members and sheeting I.S. EN : 2006 Design of steel structures General rules - Supplementary rules for stainless steels I.S. EN : 2006 Design of steel structures - Plated structural elements I.S. EN : 2007 Design of steel structures General - Strength and stability of shell structures I.S. EN : 2007 Design of steel structures - Plated structures subject to out of plane loading I.S. EN : 2005 Design of steel structures - Design of joints I.S. EN : 2005 Design of steel structures - Fatigue I.S. EN : 2005 Design of steel structures - Material toughness and through-thickness properties I.S. EN : 2006 Design of steel structures - Design of structures with tension components I.S. EN : 2007 Design of steel structures - Additional rules for the extension of EN 1993 up to grades S700 I.S. EN : 2006 Design of steel structures Towers, masts and chimneys - Towers and masts I.S. EN : 2006 Design of steel structures Towers, masts and chimneys Chimneys I.S. EN : 2007 Design of steel structures Silos, tanks and pipelines Silos I.S. EN : 2007 Design of steel structures Silos, tanks and pipelines Tanks I.S. EN : 2007 Design of steel structures Silos, tanks and pipelines - Pipelines I.S. EN : 2007 Design of steel structures - Piling I.S. EN : 2007 Design of steel structures - Crane supporting structures I.S. EN : 2005 Design of composite concrete and steel structures - General rules and rules for buildings I.S. EN : 2005 Design of composite concrete and steel structures - Structural fire design I.S. EN : 2005 Design of timber structures - Common rules and rules for buildings 49

56 Standards and publications I.S. EN : 2005 Design of timber structures - Structural fire design I.S. EN : 2005 Design of masonry structures Rules for reinforced and un-reinforced masonry I.S. EN : 2005 Design of masonry structures - Structural fire design I.S. EN : 2006 Design of masonry structures - Design considerations, selection of materials and execution I.S. EN : 2006 Design of masonry structures - Simplified calculations methods I.S. EN : 2005 Geotechnical design - General rules I.S. EN : 200 Geotechnical design - Ground investigation and testing I.S. 325: Code of Practice for Use of Masonry Part 1: 1986 Structural Use of Unreinforced Masonry I.S. 325: Code of Practice for Use of Masonry Part 2: 1995 Masonry Construction I.S. 326: 1995 Concrete I.S. 406: 1987 Masonry Mortars SR 11: 1988 Structural Timber for Domestic Construction I.S. EN : 2007 Design of aluminium structures - General rules. I.S. EN : 2007 Design of aluminium structures General - Structural fire design I.S. EN : 2007 Design of aluminium structures Additional rules for structures susceptible to fatigue I.S. EN : 2007 Design of aluminium structures Supplementary rules for trapezoidal sheeting I.S. EN : 2007 Design of aluminium structures Supplementary rules for shell structures Publications referred to Appraisal of existing structures 2 nd edition Institution of Structural Engineers Building Research Establishment Digest 366: Structural appraisal of existing buildings for change of use 1991 Code of practice for the design and installation of anchors Health and Safety Authority 2010 ETAG No Guidelines for European Technical Approvals of Metal Anchors for use in Concrete, European Organisation for Technical Approvals (EOTA) Structural renovation of traditional buildings, Report 111. Construction Industry Research and Information Association (1994 reprint with amendments) Building Research Establishment Digest 346: The assessment of wind loads. Parts 1 to 8 UEAtc Technical Guide on Anchors for use in Cracked and Non-cracked Concrete. MOAT No

57 Standards and publications I.S. 193: 1986 SWiFT 5:2011 (formerly called I.S. 193: 2006). This workshop agreement document is currently under preparation and is due to be published as Non Contradictory Complimentary Information to the Eurocodes) I.S. 444: 1996 SWiFT 6:2011 (formerly called I.S ). This workshop agreement document is currently under preparation and is due to be published as Non Contradictory Complimentary Information to the Eurocodes) 51

58 Background information on proposed procedure to determine maximum allowable building height (for buildings within the scope of Sub-section 1 Part 3)

59 Contents Page number 1.0 Introduction Proposals for Draft TGD A Methodology for determining maximum allowable building height Wind map Orography factor Altitude factor Distance from sea Distance inside town and shelter effect of surrounding buildings Terrain categories Sensitivity analysis Comparison with current practice for sites with nominally flat terrain Comparison with current practice for sites with moderately steep terrain Comparison with current practice for sites with steep terrain Conclusion References 9 1

60 1.0 Introduction The following describes the development of the updated guidance on wind loading for inclusion in the Draft Technical guidance Document (TGD A) This work is required because the current wind loading guidance in TGD A 1997 is based on CP 3: Chapter V: Part 2: 1972 (as amended in 1986). This is a withdrawn standard and also has the same field of application as the European wind loading standard EN As the core objective of the review of Part A is to update TGD A 1997 to reference the Eurocodes and remove references to conflicting standards, a simplified Eurocode compatible guidance is required to be developed. The current guidance for wind loading given in Sub-section 1 Part 3 of TGD A 1997 only applies to structures which fall within the description of paragraph i.e. houses (Category A1 buildings as defined in I.S. EN ) with not more than two floors including the ground floor, with walls of traditional masonry construction, with timber upper floors and with roofs covered with normal lightweight covering including clay or concrete pantiles. It also applies to domestic garages and other annexes to such houses. The current TGD A 1997 guidance for wind loading is based on a limiting gust wind speed V, of 44m/s. Paragraph of the TGD A 1997 states that The design wind speed (Vs) determined in accordance with CP 3: Chapter V: Part 2: 1972 as amended in 1986 should not exceed 44 m/s and goes on to describe further how this would normally be satisfied in each of the wind Zones A, B and C (Refer to Diagram 1 TGD A 1997). A limiting gust wind speed V, of 44m/s equates to a dynamic wind pressure P of approximately 1.2kN/m 2 (from the Bernoulli equation P = ½ρV 2, where ρ is the air density taken as 1.226kg/m 3 ). This limiting wind speed was derived from studies carried out in the 1950 s and 1960 s in the UK on dwellings of traditional construction and pre-dates the wind loading codes of practice. 2.0 Proposals for Draft TGD A 2011 The scope of Sub-section 1 Part 3 in TGD A 1997 limits itself to a maximum building height of 10 m where the gust wind speed does not exceed 44m/s. It is intended to retain the same scope in the proposed guidance by limiting the dynamic pressure of 1.2kN/m 2. In areas where the gust wind speed exceeds 44m/s (according to CP2: Ch V) the allowable building height is reduced accordingly so that the dynamic wind pressure is always limited to a maximum value of 1.2kN/m 2. It is intended to replace the existing map of wind zones (Diagram 1 of TGD 1997 in Sub-section 1 Part 3) with the revised values of fundamental basic wind velocity obtained from Figure NA.1 of the National Annex to I.S. EN and elaborate a procedure for determining safe building heights for buildings within a limited scope. It is anticipated that this will result in a more user friendly and accurate assessment for the maximum allowable building heights which fall within the scope of Sub-section 1, Part Methodology for determining maximum allowable building height In order to develop a simplified wind loading methodology for the TGD it is essential to understand and quantify the effects of the individual factors which influence the calculation of windspeed. The practice adopted in CP3-ChV-2 (and BS ) has been to determine the design gust windspeed. However, the Eurocode approach in EN does not directly calculate the gust windspeed, it instead jumps from a mean wind speed to a peak (gust) velocity pressure q p (z). Therefore the starting point for determining this simplified methodology must be the peak velocity pressure. For sites where orography is not significant the Irish National Annex has simplified EN expression 4.8 of as follows: For sites in Country terrain q p (z) = c e (z) q b (NA.3a) For sites in Town terrain q p (z) = c e (z) c e,t q b (NA.3b) Where: c e (z) is the exposure factor given in Figure NA.7 of the Irish NA to EN

61 c e,t is the exposure correction factor given in Figure NA.8 of the Irish NA to EN q b is the basic velocity pressure = ½ ρ v m 2 For sites where orography is significant the Irish National Annex gives two equations for use shown below: q p (z) = c e (z) c e,t q b [(c o (z) + 0.6)/1.6] 2 (NA.4a) q p (z) = ½ ρ v m 2 [ I v (z)] 2 (NA.4b) Equation NA.4a (which is applicable to the proposed procedure) is used where the building height is 50m. Equation NA.4b is used for buildings taller than 50 m (outside scope of Sub section 1 Part 3 of Draft TGD A 2011). With reference to Equation NA.4a, the primary factors affecting the wind loads are: the altitude factor c alt ; the orography factor c o ; the exposure factor c e (z); the exposure correction factor c e,t,and the shelter effect from surrounding buildings. The directional factor, season factor and probability factor may be taken as a fixed value of 1.0 in the simplified method and so can be ignored for the purposes of this analysis. The simplified proposed wind model for inclusion in the Draft TGD A 2011 includes the effects of altitude, orography, exposure factor, exposure correction factor and shelter. The expanded simplified equation for peak velocity pressure proposed for the Draft TGD A 2011 wind model, based on I.S. EN is: q p (z) = ½ρ (v b,map c alt ) 2 c e (z) c e,t [(c o (z) + 0.6)/1.6] 2 q p (z) = ½ρ (v b,map c alt ) 2 c e (z) c e,t where orography is significant where orography is not significant 3.1 Wind map (Figure 1a of Draft TGD A 2011) The wind map shown in Figure 1a of Draft TGD A 2011 is an extract from the NA to I.S. EN This map was a result of an extensive study carried out to assess the wind speeds around Ireland. Long term wind records from sixteen weather stations were used in the assessment. This map represents the most statistically up to date information available (for engineering applications). For further information on the Eurocode Wind calibration study and derivation of wind map for Ireland refer to: Orography factor (Figure 1b and Table 4 of Draft TGD A 2011) The orography factor C o is used to account for the speed up of the mean wind speed over hills, escarpments, etc. Orography can increase the peak velocity pressure by over 70% near the crest of a steep hill or escarpment. In moderately steep orography the increase in peak velocity pressure may be close to 50%. In EN , orography is considered moderate or steep terrain when the ground slope is > 0.05 (1:20). Where orography is significant and the site is located within the highlighted grey areas (refer Figure 1b of Draft TGD A 2011), the site altitude should be taken at the base of the orographic feature. This is consistent with the NA to I.S. EN leading to less conservative results and higher allowable building heights. 3

62 Overall, it is acknowledged that the proposed method can be conservative as it takes the worst case speed-up factor in each of the orographical zones. However, it should be appreciated that this method is an attempt to simplify a very complex area. 3.3 Altitude factor (Table 5 of Draft TGD A 2011) The altitude factor is used to adjust the wind speed for the altitude of the site above sea level and the height of the building above ground level and is given by: c alt = A for sites where z 10m where A is the site altitude in metres above mean sea level and Z is the height of the building. Allowable building heights in Tables 6 of Draft TGD A 2011 are based on altitudes ranging from 0 to 400 m above sea level. 3.4 Distance from sea In order to give three approximately equal step changes in exposure factor the distances from the coast in country terrain has been taken as 2km, 2km to 20km and >20km. The exposure factor C e (Z) adjusts the dynamic velocity pressure to account for distance of the site from the coast. Wind speeds reduce with distance from the coast. With reference to Figure NA.7 of NA to I.S. EN , the value of C e (Z) for each of these zones been calculated at 0.1 km, 2 km and 20 km respectively. 3.5 Distance inside town and shelter effect of surrounding buildings The exposure factor C e,t adjusts the dynamic velocity pressure to account for sites in Town terrain to account for the distance to the site from the upwind edge of the town. These factors are given in Figure NA.8 of NA to I.S. EN For sites in Town terrain the wind speed reduces as the distance in to the town increases. In order to simplify the procedure and have only a single Town terrain category, a single distance into town was taken as 1km in the draft procedure as this seems to give a reasonable compromise. The shelter effect (h dis ) from surrounding buildings was taken as 0.6h but in no case greater than 3 m. In Country terrain it is always assumed that the effective height equals the actual height and no advantage can be taken of shelter from surrounding buildings. 3.6 Terrain categories Table 4.1 of I.S. EN defines five terrain categories ranging from sea 0, to city centre IV. The opportunity was taken to simplify the five terrain categories to Sea, Country and Town in the NA to I.S. EN thus reducing the number of terrain categories to three. This approximately corresponds to the three terrain categories in BS These are as follows: Sea (category 0); Country (categories I and II), and Town (categories III and IV). Refer to Table 1 below for illustrative examples of town and country terrain. 4

63 Table 1 NA to I.S. EN and for use with Draft TGD A Assessment of Terrain category Annex A1 of I.S. EN descriptive and illustrative reference Terrain category 0 Sea, coastal area exposed to the open sea Sea Terrain Terrain category I Lakes or area with negligible vegetation and without obstacles Country Terrain Terrain category II Area with low vegetation such as grass and isolated obstacles (trees, buildings) with separations of at least 20 obstacle heights Terrain category III Area with regular cover of vegetation or buildings or with isolated obstacles with separations of maximum 20 obstacle heights (such as villages, suburban terrain, permanent forest) Town Terrain Terrain category IV Area in which at least 15 % of the surface is covered with buildings and their average height exceeds 15 m 5