Why does my flat roof leak in heavy rain?
A flat roof that stays dry in a light shower but leaks in a storm is telling you something. Heavy rain reaches weak points that light rain never gets to.
Ponding water
Flat roofs still need a slight fall to the outlets. Where water sits in puddles, it presses on the membrane for hours and finds any split or seam.
Blocked outlets and box gutters
Leaves and debris slow the outlets down. In a downpour, water backs up and spills over the edge of the membrane at box gutters and outlets, where the detailing is weakest.
Parapets and wall junctions
Where the roof meets a parapet or wall, the membrane has to turn up the wall and be capped. Wind-driven rain gets behind upturns and cappings that have failed.
Penetrations
Vents, pipes and plant supports all pass through the membrane. The seals around them age faster than the roof itself.
A worn membrane
Sun and heat break exposed membranes down until they crack or blister. Concrete slabs also crack as they move with temperature changes.
What to do
Clear the outlets if you can do it safely. Note where water appears inside and whether it follows heavy rain. Then book an inspection. We repair concrete and flat roof membranes, parapets, penetrations, box gutters and awnings. We don't work on pitched tile or metal roofs.
Every property is different. This guide is general information, not a diagnosis of your leak. Book a free inspection for advice on yours.
Leaking shower or balcony?
We'll inspect it and quote for free, anywhere in Sydney. If the tiles are sound, we can usually stop the leak without lifting them. The sealing product we use carries a manufacturer's product warranty of up to 25 years, under the manufacturer's terms.