Water ponding on sheet membrane roofing
Listed under: membranes, sheet membranes, Roof, cladding, moisture, roof cladding, sheet membrane roofing, leaks
Cause
Drainage is poor due to insufficient fall to outlets
Repair
- monitor the water drainage as well as the membrane and joints affected by the ponding. If the water tends to sit for long periods and the membrane has deteriorated, consider having the roof rebuilt with a greater slope.
- where the membrane has deteriorated to the point of replacement, rebuild the roof to incorporate more slope and fall towards the outlet.
- each outlet of a low-slope roof should have an overflow pipe to prevent the possibility of water entry into the building in case the main outlet or the downpipe gets blocked.
Cause
The drainage outlet is blocked
Repair
- clear the blockage
- flat roofs that are fully enclosed by parapets should have at least two outlets and overflows.
- each outlet of a low-slope roof should have an overflow pipe to prevent the possibility of water entry into the building in case the main outlet or the downpipe gets blocked.
Cause
The outlet is too small for the volume of water on roof
Repair
- increase the size of, or install an extra outlet
- flat roofs that are fully enclosed by parapets should have at least two outlets and overflows.
- each outlet of a low-slope roof should have an overflow pipe to prevent the possibility of water entry into the building in case the main outlet or the downpipe gets blocked.
Cause
The roof slope is not towards the drainage outlet
Repair
- install extra outlets so water falls to outlets
- where the membrane has deteriorated to the point of replacement, rebuild the roof to incorporate more slope and fall towards the outlet.
- flat roofs that are fully enclosed by parapets should have at least two outlets and overflows.
- each outlet of a low-slope roof should have an overflow pipe to prevent the possibility of water entry into the building in case the main outlet or the downpipe gets blocked.