What Causes Commercial Roof Leaks?
The most common leak sources on flat and low-slope roofs — and how to stop them.
Most commercial roof leaks start at the details, not the open field of the membrane: failed flashing around HVAC curbs, drains, vents and skylights; open or split seams; ponding water from poor drainage; clogged drains and scuppers; and punctures from foot traffic and debris. On aging roofs, UV-degraded membrane adds to the list. The good news is that nearly all of these are preventable with regular inspection and prompt repair.
Top causes of commercial roof leaks
- Flashing failures — at HVAC curbs, pipe penetrations, vents and skylights (the #1 source)
- Open or split seams — where membrane sheets lap and weld
- Ponding water — standing water from poor slope or drainage stresses the membrane
- Clogged drains & scuppers — backups that force water under the membrane
- Foot-traffic punctures — from HVAC and other rooftop service work
- Storm damage — hail bruising and wind-lifted edges
- Aged, UV-degraded membrane — brittle, cracked material at end of life
Why leaks are worse than they look
Water travels. A leak that shows up over a tenant's office may enter the roof many feet away, and moisture trapped in insulation spreads and rots decking long before it drips inside. That's why chasing a stain with patch after patch often fails — the entry point has to be found and detailed correctly.
How to prevent leaks
Twice-yearly and post-storm inspections, keeping drains clear, and repairing flashing and seams promptly stop most leaks before they start. When repairs stop keeping up, review the signs of replacement. For portfolios, we build this into a plan for property managers.
Commercial roof leaks — frequently asked questions
Homeowner tip: own a home as well as a commercial property? Our guide on why roofs leak covers the same failure points — flashing, valleys, and vent boots — that we inspect on every roof.
Chasing a leak?
We locate the real source and fix it right — not just patch the stain. Free roof assessment. Serving Dallas–Fort Worth & North Texas for over 25 years.