Code of Practice v3.0 Online
The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
The most common form of natural roof lighting used in commercial and industrial buildings comprises single skin, glass-reinforced plastic (GRP) sheets matching the profile of the metal roofing, running from ridge to eaves in continuous lengths of up to 12 m, sometimes longer. For other applications such as housing, polycarbonate sheeting is more commonly used. Polycarbonate is available in stock sheet lengths of up to 7.2 metres.
Profiled PVC roof lights are now rare as they suffer from embrittlement when exposed to UV.
GRP combines polyester resin and chopped glass fibre. AS/NZS 4256.3 requires sheets to contain a minimum of 22% glass fibre by mass and to be marked with their classification and weight.
GRP | Polycarbonate |
---|---|
Available in all profiles | Available in limited profiles |
Available in long run | Available in standard lengths |
Available in different thicknesses | Available in one thickness |
Durability >25 years | Durability >25 years |
Will lose transparency with age | Will maintain initial transparency |
Gives diffuse light | Gives direct light |
Thermal expansion 2 x that of steel | Thermal expansion 5x that of steel |
Available in tinted or opaque | Available tinted |
Reasonable light transparency | Excellent light transparency |
Polycarbonate is more popular for shorter runs and continuous widths, where clarity and stable appearance are considered an aesthetic attribute.
Stand-alone and flat-sheet roof lights may be manufactured from translucent or transparent polycarbonate, acrylic, or glass sheeting.
mm | = | g/m² |
1.1 1.2 1.3 1.5 1.9 2.1 2.5 3.0 | 1800 2000 2100 2400 3000 3300 4000 4880 |
PVC is a compound of polyvinyl chloride manufactured with stabilisers but without plasticisers that complies with AS/NZS 4256.2. Profiled PVC roof lights have a limited spanning capacity and need greater provision for expansion than other plastics or metals.
Profiled PVC sheeting ranges from 0.8 mm to 1.5 mm in thickness but is only available in a limited range of profiles. PVC softens at 80°C and will act as a smoke vent when heated during a fire. It has a service temperature of 60°C and a tensile strength of 52 MPa at 20°C.