If you own a commercial space in South Florida, you are no stranger to the need for flat roof repair. Our bountiful rainfall subjects your flat or low-slope roof to frequent tests of its water resistance. But what happens when your roof’s drains are clogged? How long can a flat roof go with insufficient drainage, and what happens when flat roof maintenance must give way to flat roof repair?
Flat Roof Anatomy
Most “flat roofs” are not flat—they are low-slope roofs, directing water toward a preferred drainage side. Your low-slope roof often meets your building’s walls at a parapet that serves to protect the roof edge and create a strong joint between roof trusses and structural walls.
The weakest point in single-ply and other membrane roofing is usually at this joint, where the membrane is mechanically fastened and a seam exists. This is also exactly where many rooftop perimeter drains are located; they are meant to channel all the runoff through scupper drains, into downspouts, and out into drainage fields.
Your commercial property may have internal drainage, where a centrally located drain on your roof carries water through your roof and then out through a drainage pipe. At PSI Roofing, we have seen every variation of flat roof drainage, and every system is susceptible to getting clogged drains.
Clogged Drains
The most serious issue with clogged drains is ponding—the build-up of water that cannot get through the scupper or internal drain. Unless you climb onto your roof after every rainstorm, you cannot easily know if you have ponding. You will only know when leaks develop, and suddenly you need flat roof repair.
The areas around drains are common sites for leaks:
- Debris is washed down by rainwater to the drain
- Debris builds up around the strainer
- The build-up forms a dam
- The dam creates ponding
- The water’s weight contributes to breaking down the waterproof seal around the drain
- Water begins running into your low-slope roof deck
Warning Signs
Obvious signs of clogged roof drains are ponding, plants growing on your roof, and leaks. Subtler signs include:
- A rise in mosquitoes in the area
- Stains on your membrane from evaporated ponds
- Algae growth
If you see any of these signs, or are concerned about clogged drains, avoid extensive flat roof repair by getting in touch with your trusted South Florida commercial roofer.
