Leak Detection
Moisture Scanning for Flat Roofs
A non-invasive way to find trapped moisture inside a roof system without cutting into the membrane to look.
Moisture scanning uses a handheld or rolling meter to detect elevated moisture levels within the roof’s insulation layer, without opening up the membrane. Wet insulation reads differently than dry insulation, which lets us map out where water has actually accumulated under the surface — even in spots where the membrane itself looks fine.
This is especially useful on older built-up (BUR) and modified bitumen roofs, where water can travel under the surface for a long time before it becomes visible as a stain, bubble, or soft spot. Scanning the whole roof, not just the reported problem area, often reveals additional wet zones the homeowner didn’t know about — which changes the scope of the repair conversation before it starts.
We use this method when a leak’s source isn’t obvious from a visual inspection alone, or when we want to confirm the full extent of water intrusion before recommending a repair versus a larger section replacement.
What a Moisture Scan Actually Shows You
A moisture scan doesn’t show you a leak directly — it shows you where moisture levels in the roof system are elevated compared to dry areas. Reading that result correctly takes some interpretation: a hot spot near a known penetration is a strong lead, while diffuse elevated readings across a wider area might indicate older, more widespread saturation rather than a single active source.
We use scan results as one input alongside visual inspection and knowledge of common leak locations, not as a standalone answer. A scan tells you where water is; understanding roofing systems tells you why it got there.
Common Questions
Can moisture scanning give false positives?
It’s possible for readings to be affected by certain roofing materials or embedded metal, which is why we interpret scan results in context rather than treating every elevated reading as automatically confirmed water intrusion.
Do I need to be present during a moisture scan?
Not necessarily, though it can be helpful if you want to see the results and ask questions directly during the process.
Need This Diagnosed On Your Roof?
We use these exact methods on every Downey inspection.