The Building Commission issued Industry Bulletin 036 – Weatherproofing of projections through metal roof surfaces in February 2014 to assist building practitioners to comply with the relevant Australian Standards and ensure compliant flashing is provided when installing projections through metal roof surfaces.
Since the bulletin’s release, the Building Commission has met with manufacturers and installers of metal roofing products to discuss ways of improving the method of flashing to the high side of the roof penetration.
A number of manufacturers of steel roofing products have advised the Building Commission that they can now provide the industry with a roof flue that has a pre-shaped upper edge that fits into the contours of corrugated roof sheeting. This enables the installer to mechanically fix and seal the pre-shaped flashing into the pans of the sheet, avoiding any ponding caused by the overuse of flexible sealant allowing full drainage of the sheet pans.
It is the Building Commission’s opinion that this method of flashing complies with clause 4.8 Projections through roofs of AS 1562.1 in that it is considered to be an adequate flashing. In all cases the high side of the projection must provide for adequate provision for drainage of all pans or corrugations.
Installers of metal roof products are not restricted to having to purchase and install a pre-shaped metal flue as long as the top edge of the flue flashing they are installing is adequately flashed using an acceptable trade method, which meets the requirements of AS1562.1. The pre-shaped flue is now being provided to save installers time scribing the flues on site.
Industry Bulletin 036 made reference to SAA HB39-997 Installation code for metal roofing and wall cladding as an Australian Standard, however, information received from installers advised that this handbook was withdrawn from publication in 2004 by Standards Australia.
Contact made with Standards Australia by the Building Commission established this handbook is still current and is being revised. A new publication is expected to be published in October 2014. The intent of our reference to this handbook was that it could be referred to by installers as a standard of good practice. In all cases, the National Construction Code Series, Building Code of Australia (BCA) applies as the regulating document. The BCA refers to AS 1562.1 as the acceptable construction manual for the installation of metal roof cladding.
Photo caption: Roof flue with a pre-shaped upper edge.