Why Water Pools on a Flat Roof
Water pools when it cannot reach an outlet. The cause may be blocked drainage, weak falls, deck movement or an outlet set too high.
Water pools when it cannot reach an outlet. The cause may be blocked drainage, weak falls, deck movement or an outlet set too high.
Falls do not guide water
A flat roof should still have a designed fall. Settlement or poor construction can leave low spots.
The outlet is restricted or too high
Leaves, moss and silt can block the route, while an outlet above the membrane creates a permanent shallow pond.
The deck has moved
Soft or sagging deck areas change the surface shape and may also indicate moisture damage below.
Why a surface patch may not help
If the roof shape or outlet is wrong, another waterproof layer can preserve the same drainage fault.
Questions about this topic
Can roof photographs answer every question about standing water?
No. Clear photographs help, but hidden underlay, fixings, deck and water routes may still need close inspection.
Should I inspect standing water by climbing onto the roof?
No. Roof work is dangerous even when the check seems quick. Photograph standing water from ground level or a safe window and leave close access to trained people with the right equipment.
When should I request a written quote for standing water?
Ask for a written quote after standing water and the access needs have been assessed. It should set out the work, materials, exclusions and any likely extras.