A flat roof gives plenty of notice before it fails. The problem is that nobody looks at it — it is the one part of the house you cannot see from the garden.
- Water still sitting on the surface 48 hours after rain
- Blisters or bubbles in the membrane
- Splits, crazing or a chalky, brittle surface
- Laps or edges lifting away from the trim
- Outlets slow to drain or backing up
- Any staining on the ceiling directly below
Why ponding matters
Standing water accelerates ageing of almost every flat roof material, adds load to the deck and makes any small defect far more likely to become a leak. A 'flat' roof should never actually be flat — it needs a fall.
What to check yourself
From a window above, or safely from a stepladder at the edge, look for standing water and lifted edges. Do not walk on a flat roof you are not certain is designed for foot traffic.