Attic Conversions. Dun Laoghaire Area Committee. 26 th January 2015

Transcription

1 Attic Conversions Dun Laoghaire Area Committee 26 th January 2015

2 Considering Attic Conversions The possibility of providing an attic conversion as a means of offering a solution has been considered by Dún Laoghaire Rathdown County Council. The conversion of uninhabitable roof space into habitable accommodation requires full adherence with statutory building regulations. Part A (Structure), Part B (Fire), Part F (Ventilation), Part K (stairs) and Part L (Energy) are of particular relevance to attic conversions The following information clearly illustrates that in most circumstances it is not possible to facilitate this option based on one or more technical issues

3 Typical Roof Profile Typical roof pitch angle of 32 to 35. Headroom Trussed rafter (more recent roofs) 35 Main ceiling joists usually 125/150x50mm. Span

4 Building Regulations 1997 Technical Guidance Document F, Ventilation Section 1: Means of Ventilation Sub-section states: Ceiling height is one of a number of factors which affects ventilation of habitable rooms. The suggested dimensions in Diagram 3 are consistent with good room design, the use of standard materials and good building practice

5 Ventilation To achieve 2.4m clearance under the ridge the following is required :- Dormer window dependent on planning permission. * a minimum span of approximately 7.5 m * at a minimum roof pitch of 35 or a minimum span of 8.4m at a roof pitch of m 35 Ceiling level minimum 2.4m above floor level (Technical Guidance Document Part F) 7.5 m

6 Ventilation The area of headroom at ceiling level (minimum of 2.4m above floor level) should be at least 50% of the area at 1.5m above floor level. The area A in red should be at least 50% of area B in blue. This is as as in Technical the Guidance Documents- Part E, F (Building Regulations Regulations 1997), Diagram 2009, Diagram 5. Page 8. 3, Pg.11 A B 2.4m 1.5m Ceiling level minimum 2.4m above floor level

7 Ventilation In typical DLR dwelling dating from 1970 s In onwards, Cois Cairn, as Bray,as the illustration the illustration shows shows the pitch the pitch is 40 is 40 and and the the span span is 7m. is 7.0m. The The area area in red in red would be be only approximately 1/4 ¼of of the the area area in blue. in blue 1.5 m 2.4 m

8 Ventilation 1.1m 2.0 m 2.4 m m 2x1.1 maximum Span of approximately 8.5 m required for 2.2m wide room in attic. Prior to deeper floor joists and insulation works allowed for.

9 Typically prefabricated roof trusses are used in houses at 600mm centres. To facilitate attic conversion, the trusses need to be removed, this requires expensive alteration and replacement structural members to be inserted. Structure

10 Structure HOMEBOND HOUSE BUILDING MANUAL Page. 181 Structure It is possible to use purpose designed prefabricated dormer trusses at design stage. However they involve "In dormer roofs the need to provide clear space (i) extra costs of adequate width and height to accommodate (ii) may have roof height and pitch implications and rooms means that the structural form of the roof (iii) planning implications differs significantly from a conventional roof space. The design of the roof structure must take this into account, and ensure that sizing and disposition of members is adequate".

11 Structure Insulation to be inserted to building regulations standard between and under rafters. The typical headroom here before inserting new floor joists at a pitch angle of 35 and a span of 7.0m, is 2.2m, at 32 pitch it is smaller. After inserting new floor joists in lieu of ceiling joists this figure is reduced. Trusses strengthened with extra members Main ceiling joists not strong enough to support floor loads of attic room. New stronger deeper floor joists have to be inserted.

12 Equipment and Services Services and equipment that may have to be altered, relocated or replaced - chimney stack - flues -gas boiler etc. - water storage - electrical cabling/trunking, equipmen - ventilation/extraction ducting

13 Access Existing staircase with landings TYPICAL SECTION TYPICAL FIRST FLOOR PLAN BEFORE ATTIC STAIRS INCLUDED

14 Access Attic floor space shown in blue hatch New staircase with landings Existing staircase with landings Existing staircase with landings New staircase with landings taking up space of twin bedroom and now only useable as single. SECTION FIRST FLOOR PLAN

15 Access New staircase required minimum headroom of 2.0m required Attic floor space shown in blue hatch Existing staircase with landin New staircase with landings Existing staircase with landings New staircase with landings taking up space of bathroom, that now has to be relocated. SECTION FIRST FLOOR PLAN

16 Fire Safety BUILDING REGULATIONS Technical Guidance Document B - Fire safety Section B1 :- Means of Escape in Case of Fire :- Sub-section provisions that have to be included in cases where the new attic storey floor will be more than 4.5m above ground level (probably a two storey house). It stipulates the folowing requirements :- - fire resisting enclosure construction be provided to form protected staircase enclosure - fitting fire resisting doors - automatic smoke detection and alarm system - provision of escape window/doors from the new third storey - layout and configuration of the escape/stairs to comply with the requirements of this section. - separate attic floor by fire resisting construction

17 Fire Safety Escape window to comply with Building Regulations TGD S Clear opening minimum 0.33 sq.m. and minimum 450mm high Max 1.1m, min 0.6m Max 1.7 m Area beneath window should be clear of obstructions to enable escape and/or rescue. For example : conservatory/back addition.

18 Conclusion Technical Issues which can prove problematic in relation to Attic Conversions: Ventilation Structure (roof trusses etc.) Equipment/Services located in the attic Access and its adverse affect on existing living space Fire Safety

19 End of Presentation 26 th January 2015