Flashings are installed in masonry to prevent the migration of rainwater to the inside of the building.
Like damp-proof courses, flashings must be water resistant and sufficiently robust to remain intact during construction.
They must not disrupt the structural function of the masonry. In some circumstances, flashings may also serve as damp-proof courses.
A suitable specification for flashings is as follows. In some states, additional requirements may apply.
Flashings shall comply with the Drawings, Building Regulations and relevant Standard (AS 3700, AS/NZS 2904).
? Metal and metal-cored flashings shall not be used in locations that expose them to saline ground water or rising salt damp.
? Metal flashings shall be compatible with the materials with which they are in contact, and shall not give rise to electrolytic action. If there is potential for electrolytic action to occur, flashings shall be isolated by inert materials.
? Flashings intended to hold their shape shall be manufactured from rigid material. (e.g. metal cored material)
Unless stated otherwise flashings shall consist of one of the following options: Flashing in Concealed Locations (e.g. cavity flashings) shall be one of the following:
? Uncoated annealed lead having a mass not less than 10 kg/m² in lengths not exceeding 1.5m, but shall not be used on any roof that is used to catch potable water;
? Uncoated copper having a mass not less than 2.8 kg/m² and having a thickness of 0.3 to 0.5 mm;
? Bitumen coated metal (normally aluminium) with a total coated thickness of 0.6 mm to 1.0 mm;
? Zinc coated steel with a thickness not less than 0.6 mm;
? Embossed/quilted polyethylene sheet with an average thickness not less than 0.5 mm
Flashings in Exposed Locations (e.g. flashings from the roof to masonry wall) shall be one of the following:
? Uncoated annealed lead having a mass not less than 20 kg/m² in lengths not exceeding 1.5 m, but shall not be used on any roof that is used to catch potable water;
? Uncoated copper having a mass not less than 2.8 kg/m² and having a thickness of 0.3 to 0.5 mm;
? Bitumen coated metal (normally aluminium) with a total coated thickness of 0.6 mm to 1.0 mm;
? Zinc coated steel of thickness not less than 0.6 mm.
