Roof Leak or Old Stain? How to Tell if You Have a Leak

LESLIE: Shana in Massachusetts is on the line with a roofing question. What’s going on at your money pit?

SHANA: I recently had a roof replaced in the fall and I’m wondering about a leak that was there before they did it. And it’s leaking where the chimney is. The house isn’t 100 years old but it’s in pretty good shape.

TOM: OK.

SHANA: And in that same spot, I still see a darkness.

TOM: So, Shana, here’s what I think: if you had a leak that was significant, you would actually be seeing water, you’d be seeing swollen drywall. Slight differences in the color of the drywall are not really going to signify whether or not you have a leak or not. Hey, I had a leak in my chimney flashing in my 100-year-old house just 2 weeks ago and I figured out that a piece of my flashing had gotten loose. But when it leaked, it really leaked. We had water coming down the chimney inside the attic space.

So here’s what I would do. When you get that kind of a stain, what you have to do is you have to prime over it. You can’t just paint it with ceiling paint. You have to use a primer because that’s what really seals in that discoloration. If you prime it and paint it and then you start to see it form a stain again, then I might worry. But from what you’re describing, I don’t see any evidence that you have an active leak.