How to Repair Roof Leak

LESLIE: Bob in Texas is on the line and has a question about how to repair roof leak. What’s going on?

BOB: Well, we’ve had a long drought out here in West Texas. And we finally got some rain and lo and behold, I have a leak. And I remember tuning into your show some time ago where you guys mentioned a product that was clear that could be applied with a paintbrush that would penetrate through the roof and then seal it. And I could not or I did – I couldn’t remember the name of the product. And I’ve been trying to find it here in Lubbock, Texas and having no luck at all. And I just thought, “Well, I just need to call you guys and see if you can remember that and tell me what it is.”

TOM: Well, Bob, that’s going to be a bit of a mystery to me because it doesn’t sound like the kind of thing that we would recommend to repair roof leak. But let me just ask you more about this leak. Do you know where it’s occurring? Do you know if it’s coming through, say, a cracked shingle or is it coming around a chimney? Is it coming around a pipe? What do you know about it?

BOB: Where the slope of my roof joins my patio. And the patio roof is flat. So, I’m thinking probably what’s happening is it’s backing into the den past the wall but …

TOM: Right. Yeah. That’s a tough spot to flash. And it’s also a tough spot to do a sort of an easy patch repair to it. You know, all these types of roof products that you apply after the fact, they’re usually asphalt roof cement. And they’ll work for a while but they tend to dry up pretty quickly. When you have an intersection like that where you have a pitched roof that comes into a low-slope or a flat roof, you’re right: the water can back up there and do the force of kind of against gravity and due to that force can actually sort of work its way up into the roof surface.

The right way to flash that – and you’re not going to want to hear this – but the right way to flash that is to have the flat roof basically go right up and under the roof shingles. So the flat-roof material would go to that intersection and then up and under the roof shingles and probably up maybe 3 feet under them. And then the roof shingles would continue over that, creating a big overlap there where it would be virtually impossible for any water to back into it. And I would start that project with a product called “ice-and-water shield,” which is sort of a tacky, 3-foot-wide, roll-on sheet that literally glues itself to the deck surface and will stop all water from getting through. So that’s the best way to permanently repair roof leak.

Short of that, it’s OK for you to use an asphalt cement product to try to patch it. But I’m just concerned that it’s something you may have to do time and time again. If it does develop that way, then maybe you could choose to make the bigger repair later.

BOB: And you say that that is ice-and-water shield?

TOM: Yes, ice-and-water shield. Yep. That’s the right first step for that and that goes underneath the roof shingles. Nice thing about that, too, is if you ever have roof shingles that blow off, your roof still won’t leak because it remains watertight.

BOB: Well, I certainly appreciate your help with that.

TOM: Alright, Bob. Well, thanks so much for calling.