A waterproofing system is designed to resist water.
But it should not be expected to compensate for poor drainage forever.
On many flat roofs, the problem does not start with the membrane itself.
It starts with water that has nowhere to go.
Poor falls, blocked outlets, undersized drainage, badly positioned rainwater outlets, ponding water and poor maintenance can all increase the risk of roof failure.
Standing water creates constant stress on the waterproofing system.
It can expose weak details.
It can accelerate ageing.
It can increase the risk of water ingress at laps, outlets, penetrations and terminations.
It can also hide early warning signs until the damage becomes more serious.
This is why drainage should never be treated as a minor design detail.
Before approving a roof repair or refurbishment, it is important to ask
- Does the roof drain properly?
- Are there enough outlets?
- Are outlets blocked or restricted?
- Are falls adequate?
- Is ponding water present?
- Are overflow provisions in place?
- Is regular maintenance being carried out?
- Will the proposed system tolerate the actual drainage conditions?
A new waterproofing layer may improve the roof surface.
But it will not automatically correct poor drainage.
If water is allowed to remain on the roof for long periods, even a good waterproofing system can be placed under unnecessary stress.
Good roof performance depends on more than the membrane.
It depends on the full roof system working correctly.
Drainage is not just about removing water.
It is about reducing risk.
Inspect → Assess → Specify → Perform
Drainage is not just about removing water. It is about reducing risk.