RBW does not include building work for which a building consent is not required.

Transcription

1 Document type: Practice Note Title: Certificate of Design Work (CoW) Document number: AC2261 Version: 1 1. Purpose The purpose of this practice note is to provide some clarity around the content and requirements of the Certificate of Design Work (CoW), which is provided in respect to Restricted Building Work (RBW). 2. Legislative requirements Section 45 of the Building Act 2004 states that if an application for a building consent is accompanied by plans and specifications that contain design work (relating to building work) that is RBW, then that design work must be carried out or supervised by one or more licensed building practitioners who are licensed to carry out or supervise that work. Further, that the plans and specifications that contain the design work must be accompanied by a certificate of work:- a) provided by one or more licensed building practitioners who carried out or supervised that design work; and b) that identifies that design work; and c) that states:- i. that the design work complies with the Building Code; or ii. whether waivers or modifications of the Building Code are required and, if so, what those waivers or modifications are RBW does not include building work for which a building consent is not required. 3. Restricted Building Work (RBW) - Design An application for building consent must include a CoW if the design involves RBW. The design includes the preparation of any drawing, specification or other documentation required to demonstrate compliance with the Building Code. Only a licensed building practitioner (LBP) is able to design or supervise the design of RBW and issue a CoW. If the designer does not provide a CoW the application cannot be accepted. The Regulations require that the following design elements be designed or supervised by an LBP:- the primary structure, external moisture management system, or the fire-safety system For a full list of definitions refer to the Building (Definition of Restricted Building Work) Order 2011 Primary structure means a) building elements that are intended to contribute to its ability to withstand vertical or horizontal loads (for example, its beams, bracing, columns, foundations, roof, subfloor framing, and walls); and b) includes any part of its primary structure Page 1 of 5 June 2014 AC2261 (v.1)

2 The primary structure includes all structural elements that transfer imposed loads within the building from the roof down to natural ground. Structural elements include rafters, ridge beams, trusses, roof and wall bracing, wall framing and lintels, foundations, slabs, etc. Although trusses are manufactured off-site they must still be incorporated and referenced in the CoW. The designer is responsible for checking to ensure that the wind loading is correct and that all point loads have been appropriately transferred. A simple comment on the CoW will suffice, such as, trusses manufactured by (name of truss maker) as per PS1 attached. External moisture-management system means (a) A system (whether comprising only one or 2 or more building elements) that is intended to provide i. Resistance to the penetration of the building by moisture from outside it; or ii. Resistance to the accumulation within the building s fabric of moisture that has penetrated it from outside the building; and (b) (c) Includes any of the building s building elements that are, or form part of the damp-proofing, roof-cladding or a roof cladding system, a ventilation system, wall-cladding or a wallcladding system, or water-proofing; and Includes any part of its external moisture-management system The external moisture-management system includes all elements of the external envelope that deflect moisture away from, or provide an impenetrable barrier into, the building. For example: cladding material, flashings, joinery and any secondary measures such as the drainage cavities and any means for venting these cavities. Note: internal membranes such as those used in wet areas (e.g. showers and bathrooms) are not RBW; however, Council may require a producer statement for the installation of these products. Fire-safety system, in relation to a building, means those of its building elements that are intended to protect people, household units adjacent to it, or other property, from fire or the effects of fire; and includes building elements that are, or are parts of, a) emergency warning systems; and b) systems intended to enable or facilitate the evacuation of the building in an emergency; and c) systems intended to enable or facilitate fire-service operation; and d) systems intended to suppress or control fire or smoke The design of fire safety systems does not include manufacturer or referenced design (e.g. the design of a proprietary alarm system); however, these proprietary systems should be referenced, in the CoW. The design of fire walls that separate residential units is RBW, and as such, must be identified as part of the design work on the CoW. Page 2 of 5 June 2014 AC2261 (v.1)

3 4. Definitions of house and small to medium apartment buildings The following definitions are taken from the Building (Definition of Restricted Building Work) Order These definitions must only by used for the purposes of this Order. (Definitions from documents such as the Acceptable Solutions or other Building Regulations must not be used or confused with the definitions in this document and are purely for the purposes of determining whether certain work is RBW). House means a free-standing, fully detached building consisting of a single residential unit (or a single residential unit and 1 or more residential facilities) Residential unit means a building, or part of a building, that is so designed that it is more suitable for being lived in by a single household or family than for any other use. Attached buildings such as conservatories and decks are not considered RBW. A minor household unit falls with the definition of a residential unit and is therefore RBW. A sleepout is not considered a residential unit. Residential facility means a part of a building that is not a residential unit, but is a facility (for example a corridor, foyer, garage, laundry, lift, sauna, or storage unit) whose principal or only purpose is ancillary to the use of a residential unit in the building (or shared between 2 or more residential units in the building). Residential facilities must be those facilities used directly in relation to the residential unit(s). Outbuildings such as garages, carports, bridges, swimming pools, sleep-outs, etc. are excluded from the RBW. Small-to-medium apartment building means a building that contains 2 or more residential units or residential facilities (but excludes apartment buildings over 10m in height and those that include non-residential uses such as retail space). Small to medium apartment buildings include duplexes and terraced houses i.e. two or more houses separated by a fire wall and includes apartment buildings or townhouses, tenanted by way of a right to occupy, such as those within retirement villages. Shared facilities and spaces in apartment buildings are also RBW. Maximum calculated height, in relation to a building, means the vertical distance between the highest point of its roof (excluding structures such as aerials, chimneys, flagpoles, and vents) and the lowest point of the ground. 5. Certificate of Design Work (CoW) The memorandum (CoW) is a regulated form (Form 2A) and must contain all information prescribed on it. The designer can print this form onto their own letterhead or attach a logo, however they cannot alter the content. All parts of the design of RBW must be included in the CoW. Page 3 of 5 June 2014 AC2261 (v.1)

4 Council will only accept a building consent application if the CoW has been completed in a manner that confirms all aspects of the RBW is covered. A CoW comprises of a number of pages and therefore, must be able to be identified as a single document. There will be times when more than one designer has done Design RBW. In these cases, all the designers involved need to make sure their information aligns with any others involved in the application. This is so that when the Memorandum (Certificate of Design Work) is read together it is clear to the council that all the Design RBW has been done or supervised by LBPs licensed in the Design class. Two LBPs work on different aspects of the plans and specifications that are RBW (e.g. one designs the foundations and slab and the other designs the balance of the superstructure), then each LBP would be expected to provide a CoW for their respective parts. A designer may choose to cover all RBW including the work performed by another LBP. In this case the designer must provide a CoW covering all elements of design. This is similar to the scenario mentioned in the definition of primary structure regarding trusses. An engineer will often design foundations based on an investigation by a geotechnical engineer. In this case, a CoW is not required from the geotechnical engineer as sub-surface investigation is not RBW. In the event that the soil needs to be strengthened, such as might be the case where soils are affected by liquefaction or other types of instability, then such strengthening is part of the RBW and must be included in the CoW. It is the lead or sole designer s responsibility to ensure that all aspects have been incorporated into the overall design. The lead or sole designers must provide all supplementary design and proprietary product information as part of the building consent application and note on the CoW, that they have relied, on the specialist design of others. Building consent applications supported by a CoW form an LBP whose status cannot be verified, will not be accepted. 6. Licensed building practitioners and design classes The design class for LBPs includes persons that have successfully applied under the Building (Designation of Building Work Licensing Classes) Order 2010 to be licensed. Chartered professional engineers (registered under the Chartered Professional Engineers of New Zealand Act 2002) and Registered Architects (registered under the Registered Architects Act 2005) are automatically deemed to be LBPs. The designer providing the Memorandum (Certificate of Design Work) must work within their individual competency (i.e. their personal professional expertise). Design LBPs must hold a license for one of the three practice areas (Design 1, 2 or 3); this depends on the category of building (for licensing purposes) that they were assessed against. It is important to note, however, that a design LBP is not limited to only designing categories of building that they were originally assessed for. A design LBP may submit a design on any category of building if they believe it is within their individual competency. Page 4 of 5 June 2014 AC2261 (v.1)

5 7. References Building (Designation of Building Work Licence Classes) Order 2010 Building (Definition of Restricted Building Work) Order 2011 Building (Forms Amendment) Regulations 2011 For further information about LBP or RBW refer to Ministry of Business, Innovation and Employments website Page 5 of 5 June 2014 AC2261 (v.1)