Common challenges with flat roofs, balconies and basements.

While poor-quality waterproofing is a significant contributor to strata defects, there are several common problem areas that, if neglected, will likely lead to water ingress, affecting your tenants and your property.

Flat Roofs

Flat roofs can’t rely on the natural slant of a sloped roof to remove water, so it’s imperative to have a comprehensive solution design that includes adequate drainage. Without it, water is likely to pool on your roof after heavy rain or storms.

Ongoing pooling can damage your waterproofing membrane. Water will seep into the ceiling cavity through tiny cracks and eventually into the apartments or offices below with nowhere to go but down.

Other potential problems impacting roof waterproofing include poor-quality membrane installation, clogged drains, crocodiling or blistering on the surface or flashing failures due to incorrect priming or installation. Extreme climate conditions may also hasten general wear and tear on your waterproofing membrane.

If undetected and untreated, water ingress from your rooftop will likely cause issues in the apartments or offices beneath, including mould, efflorescence and concrete spalling.


Balconies are exposed to the climate, and without quality, waterproofing can be a prime channel for leaks. Your waterproofing solution should allow for adequate flow away from the building façade, with suitably sized drains and the correct number of drain outlets.

It’s also essential to choose the right waterproofing membrane for the environment, suitable substrate layers and coatings, plus careful remediation to ensure tiles or other layers above the membrane are watertight.

Water that seeps into walls from balconies may not be immediately visible but can eventually manifest as mould, flaking paint, cracks or crumbling plaster. If left untreated, this can result in efflorescence, concrete spalling and concrete cancer.


Given their underground location, basements are frequently damp and vulnerable to water seepage from the surrounding earth. This can worsen with increased pressure or a rising water table after heavy rain. Broken or damaged piping or water ingress from ineffective waterproofing elsewhere in the building can also cause problems in basements.

Typically, signs that you have a waterproofing issue might include mould, rust stains on metal surfaces, flaking paint, crumbling plaster, rotting wood or stained and discoloured floors.

Efflorescence is also very common – a mineral deposit build-up (it looks like a white powdery coating) that can affect brick, concrete and clay tiles.

Vertical cracks in basement walls often appear with age; however, they may also be a sign of moisture. Horizontal cracks usually occur when pressure is on the other side – so you need to get them checked urgently.

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