Waterproofing problems

According to a March report by the Property Council of Australia, waterproofing failures rank among the top 10 building complaints from residential owners’ corporations on behalf of owners. These failures also account for a large percentage of accepted insurance claims.

Most people associate water ingress problems with older homes. It would be nice to be able to feel confident when purchasing new property that such problems were highly unlikely. Unfortunately this is not the case. Despite stringent regulations, many new buildings develop leakages within the first year. That first big rain after a building’s completion is the time when builder and architect alike wake in a cold sweat dreading phone calls to report leaks.

So why is it so hard to stop water entering a building? Haven’t we been living in wet environments long enough to know how to keep it out?

Firstly water can behave quite unexpectedly. It has the annoying ability to climb upwards and across using capillary action. It also gets blown backwards by wind and can be sucked into niches or cracks. It can creep through a layer of brickwork or up under a window sill and before you know it your internal linings, soft furnishings and furniture are wet.

Another part of the problem is new and untested techniques and technology, but the major reason for building leakages is poor workmanship. The building element known as flashing is the key to keeping water outside. Flashing is metal sheet which needs to be installed at all junctions between different building materials, especially around doors, windows and roof penetrations. If it is installed wrongly, or omitted altogether, water may find a path into the building.

One common problem area is at the base of walls. The best practice is to provide a set-down, or level difference between the internal floor level and the base of the wall. Flashing is then built into the base of the wall to drain any water to the outside. This combination of flashing and setdown is generally an efficient safeguard. Failure to install this very quickly results in water entering the building at floor level and consequent damage to floor coverings. Other problems commonly occur around window sills, roof penetrations and box gutters.

Waterproofing problems can also occur in wet areas if the water-proof membrane is not properly installed. This can result in water entering the structure of a building, including walls and floor, causing damage to this structure and any finishes. Often this is evident in adjacent rooms where wall paint persistently peels and mould may occur. Unfortunately if a membrane fails there is no other way to repair the problem than to replace it, which means firstly removing tiles or other finishes. Another frequent problem in internal wet areas is over-reliance on silicon sealant as waterproofing. Silicon is easily damaged and tends to degrade when constantly exposed to moisture. This can lead to water leaking into joinery, under wall tiles and other finishes causing moisture damage and mould.

Ideally you should check when purchasing a newly constructed apartment or home that the building has been constructed according to the minimum standards of the Building Code of Australia and the Australian Standard for Waterproofing. The Master Builders Association of NSW has recently released a publication entitled Guide To Internal Wet Area Waterproofing, which it hopes will assist waterproofing contractors to update their practices.