Water – Does a device exist that can help find the source of a leak in a flat roof


My Dad has a flat roof over his garage. It's covered with tar and felt.

We had an unusually hard and cold winter last year (Republic of Ireland) and since then the roof has developed a leak.

We've made several attempts to patch it, with no success. We know where the water is exiting the roof but we can't tell where it's getting in.

Is there some device that will trace the water from the leaks exit back to where it's getting in under the felt?

I'm thinking more tricorder, and less dowsing rod 🙂

Best Answer

Knowing the type of roofing system on the home would greatly assist in giving advice on how to track the source of the leak. A moisture meter is what you're thinking of, but in general, a moisture meter will not help you track a leak any more than simply doing so with your eyes. It is used more generally as a way to prove whether water exists in the roof system or if, let's say, a plumbing issue is to blame for the interior leak.

Most flat roofs are never truly flat and have slight slopes and ponding areas. My recommendation would be to pinpoint the location that the water is entering inside of the building while on the roof, and then tracking it back uphill in a "V" shaped pattern. Check around flashings and seams for discrepencies if a hole is unable to be located.