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Finding the Source of a Leak in a Chimney

  • Transcript

    LESLIE: Next up, we have a call from Tom in Georgia who has a leaky chimney.

    Tom, where is it leaking from?

    TOM IN GEORGIA: It’s leaking from the very top of the chimney, which is very unusual because you’d typically expect it to be along the roof line. But that’s fine. The rest of the flashing where it meets the roof is fine. It’s up at the top of the chimney. It’s a stucco chimney and I know that it can get kind of porous but I mean this is ridiculous. We’ve been trying everything.

    TOM: Where is the leak coming in? Is it getting into the flue and leaking down out of a fireplace or at – where are you seeing the water evidence itself?

    TOM IN GEORGIA: Actually, in comes in in a corner where it looks like some plywood structure has been built and the stucco is on the outside of it. So it’s not coming into the flue. It’s outside of that. Leaks through the inside, runs down the plywood portion and some 2x4s that are part of the structure.

    TOM: So wait a minute; let me understand something. Is this a real chimney or is it a chimney chase? You’re talking about plywood. Is it a wood frame around a metal pipe?

    TOM IN GEORGIA: It’s an insert chimney.

    TOM: Ah, OK. So this is basically a frame that’s supposed to look like a chimney but inside of that there’s a flue pipe that goes to the roof.

    TOM IN GEORGIA: Correct.

    TOM: OK. Do you know and have you ruled out that there is no leak inside of this chimney chase around that flue pipe?

    TOM IN GEORGIA: Yes. Ruled that out.

    TOM: OK. Alright. Up near the top, describe the construction of the chimney chase around the top. In most cases there’s going to be a sheet metal top where the insert flue pipe comes up through it and it’s caulked around.

    TOM IN GEORGIA: Well yes, it’s caulked around and it has a chimney cap on top of it. It’s made out of metal.

    TOM: Right.

    TOM IN GEORGIA: And then another piece from that flue cap goes above there to keep rain from getting in and it has – it’s like a little roof itself.

    TOM: But I mean there’s no chance any water is getting in there and running down behind this plywood structure?

    TOM IN GEORGIA: No, it comes in right in a corner.

    TOM: Alright, it sounds a lot like flashing. Have you done this? Have you gone up on the roof – I don’t know if you can walk this roof, if it’s not too steep.

    TOM IN GEORGIA: It’s kind of like Mount Everest only different. (Leslie chuckles)

    TOM: Oh, well that sounds like it is too steep. That sounds pretty steep. One of the things that you could do is to try to put a diverter around the chimney so that the water doesn’t collect near the bottom of it.

    TOM IN GEORGIA: It’s not coming in at the bottom; it’s coming in at the top.

    TOM: Right. But I mean it’s on the downhill side, right? Does the water go against it?

    TOM IN GEORGIA: It’s coming in a corner and the only thing I can think of is that the stucco has become cracked or whatever at that point and it’s seeping in behind there.

    TOM: Alright, well it sounds to me like the only other possibility here is some crack in the stucco and it might be one that you can’t see. It might be one that you have to physically look for very close to the chimney structure. Because if you do have a break in it, it’s possible the water is getting in there. It doesn’t take much of a crack to get through and with the kind of structure you’re explaining, there could be a lot of expansion and contraction that’s going to open that up just enough to let the water through.

    LESLIE: Is there an overall sealant that he can put over the entire structure or something he can put on the inside to sort of plug the general area where the crack might be?

    TOM: Well if you can identify the crack, I would recommend sealing it with a silicone caulk. But the problem is you’re going to have to get up there to find it. If it’s happening that consistently and that high up, it sounds like that’s the only other possibility if you’re convinced it’s not the flashing. It’s almost always the flashing but if you’re telling me that you’re convinced it’s not the flashing, then it’s got to be coming up higher into the brick. It sounds like you’ve got a good roof surface on that, the way the structure is designed.

    TOM IN GEORGIA: So silicone caulking, that comes in – there is roof silicone caulking that’s pretty good?

    TOM: Oh, absolutely.

    TOM IN GEORGIA: It’s not going to discolor?

    TOM: No.

    TOM IN GEORGIA: Well perhaps you and I working together contacting the Mount Kilimanjaro team (inaudible, Tom and Leslie laugh) get together and do this.

    LESLIE: I will send a Sherpa your way and we can get this all taken care of.

    TOM: (laughing) There you go. Tom, thanks so much for calling us at 1-888-MONEY-PIT.

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