WATERPROOF MEMBRANE DECKS
Waterproof membrane decks incorporate a waterproof membrane that is installed over a timber substrate. In essence they are a low pitched roof surface that will collect water which needs to be drained.
Typically, they are constructed with timber framing, a plywood substrate and waterproof membrane and could be over a habitable living space.
To drain the water the design of the deck will incorporate a range of details such as internal gutters and drain points, and drainage scuppers.
Fully enclosed decks have a high risk factor compared to decks that are open ended. Where water does not effectively drain from a deck surface, the waterproofing will deteriorate faster and the risk of water entry through waterproofing membrane joints or a small area of damage is greater.
Open ended decks can be drained into an external gutter system therefore negating the need for a complex drainage system.
Tiles directly stuck to the membrane were quite common back in the 90’s. This created a problem of the membrane being damaged over time. However the Building Code E2/AS1 now requires as an acceptable solution is a cavity installed between the deck waterproofing membranes and trafficable surfaces to allow for inspection and maintenance of the membrane.
This cavity requirement instantly rules out a normal tiling installation such as tiles fixed directly to the membrane surface.
Tip: Good design, detailing and construction practices can effectively address the known trouble spots.