Why Is My Commercial Roof Leaking? 5 Common Causes

Understanding the cause of a commercial roof leak is the first step to finding the right solution. Here are the 5 most common causes.

1. Seam Failure

The #1 cause of commercial roof leaks. Heat-welded or adhesive-bonded seams on TPO and EPDM systems fail over time from thermal cycling. Once a seam fails, it's a direct water entry point. If seams are failing across an aging membrane, individual repair is impractical — silicone coating restoration seals all seams simultaneously.

2. Flashing Failure

The second most common cause. Flashing at penetrations (HVAC units, pipes, drains), wall-to-roof transitions, and roof edge terminations are vulnerable to failure. Traditional metal and bituminous flashings crack, separate, and lose adhesion. Annual inspection and prompt re-sealing extends flashing life significantly.

3. Membrane Puncture

Physical damage from foot traffic, equipment installation, hail, or falling objects. Foam roofs handle this better than sheet membranes — repair is simpler and the seamless surface self-isolates damage.

4. Ponding Water

Chronic ponding accelerates membrane deterioration — even systems rated for ponding water eventually wear faster in standing water zones. Addressing drainage inadequacy is the fix, not just patching the leak.

5. Age and UV Degradation

Membranes become brittle and lose elasticity with age, making them more susceptible to cracking and failure under thermal stress. When a roof leaks primarily due to age, restoration (not repair) is usually the most cost-effective solution.