Cannot Locate Leak on Commercial Roof: What to Do?

One of the most frustrating roofing problems: water is getting in, but you can't find where it's coming from. Here's a systematic approach to finding and fixing elusive commercial roof leaks.

Why Commercial Leaks Are Hard to Find

Water doesn't always drip straight down. It can enter the roof in one location, travel along the membrane or through insulation, and exit the ceiling 20–30 feet away from the actual breach. This makes visual inspection of the interior useless for pinpointing the source.

Step 1: Systematic Roof Inspection

Start on the roof and systematically inspect every potential entry point: seams, flashings, penetrations (HVAC units, pipes, drains), parapet walls, and any areas where the membrane transitions. These are where 90%+ of leaks originate.

Step 2: Infrared Scan

An infrared (thermal) scan performed at dusk can identify wet insulation by detecting temperature differences as the roof cools. Wet areas retain heat longer than dry areas, appearing as warm spots on the scan. This is the most effective tool for locating hidden moisture infiltration.

Step 3: Electronic Leak Detection

For roofs that are difficult to scan, electronic leak detection systems can apply a low-voltage charge to the membrane and identify breaches through electrical conductivity testing.

The Spray Foam Solution

For roofs with chronic, hard-to-locate leaks, a spray foam restoration eliminates the problem entirely. Rather than hunting for individual breaches, foam creates a completely new seamless surface over the entire roof — eliminating every existing entry point at once.