DECO ARTS COMPLIANCE CASE STUDY
The existing roof of an art deco house with continuous parapet walls, a very low-pitched roof (3°) and a 200 mm wide by 50 mm deep internal gutter draining to an original galvanized steel rainwater head, requires re-roofing. The existing roof is bitumen-impregnated membrane roofing which replaced a similar roofing material approximately 30 years ago. There is no insulation or building paper in the roof.
| Step 1. Identify the aspects of the proposed design that fall outside the scope of Acceptable Solutions
| This will depend on exactly how the job is specified.The existing roofing must be removed. A new ply substrate will be required and a new membrane roofing system could be installed.However, as there is no insulation or building paper, a recommendation would be to replace the substrate and install insulation and a building wrap in the roof. This would also require new framing to be added to provide the minimum 25 mm air gap required between the insulation and the roof substrate, so the roof pitch could be increased at the same time. The new framing would also enable a new internal gutter to be built to meet the current Acceptable Solution requirements.
| Step 2. Identify the Building Code clauses for which performance must be demonstrated by the design and supporting documentation.
| The Building Code clauses to be addressed by this Alternative Solution are:• B2 Durability• E2 External moisture• H1 Energy efficiency
| Step 3. Identify the performance criteria that apply.
| The performance criteria that apply include:• B2.3.1 Building elements must have a not less than 15 year durability• E2.3.1 Roofs must shed precipitated water• E2.3.2 Roofs must prevent penetration of water• H1.3.1 The building envelope must provide adequate thermal resistance.
| Step 4. Select the most relevant compliance path(s).
| The most relevant compliance path options could be:• Compliance path 3 – comparison with in-service history• Compliance...
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