Waterproofing around stovepipe.

[bokehman]

How do you make the join between the stainless stovepipe and the masonry chimney waterproof? Every time it rains really hard I get water dripping down the outside of the flue. The pipe passes through 2" of cement at the top of the chimney but the heat has made it porous around the pipe.

 

[begreen]

Normally the flue cap has a 2-3" collar on it that the ss liner slides through. That acts as an effective water dam. Other caps have a raised lip where the pipe goes through so the water sheds away from the pipe. That system may have a storm collar above this lip.

It's easier to to spot the problem in a picture. Any possibility of posting a shot of the flue cap?

 

[bokehman]

Hi, I know this looks a terrible mess in the pictures but the cracks are just shrinkage lines and not the problem. When it has the finishing coat it will look fine. The problem is, in heavy rain, water runs down the SS liner and enters the chimney between the liner and the cement.

 

[Hogwildz]

Seal around the pipe where it meets the concrete with hi temp silicone. Work it in good with your finger.
Then put a storm collar around that pipe and sel it same way.

 

[begreen]

A storm collar will help for sure, but I wouldn't trust the cement joint. It can't flex with temperature variations. I'd put a proper flue cap on, sealed with HT silicone, then a storm collar, also sealed.

 

[Joey Jones]

Seal around the pipe where it meets the concrete with hi temp silicone. Work it in good with your finger.
Then put a storm collar around that pipe and sel it same way.

Second the motion by hogwildz....use Rutland high temp silicone rated to 500 degrees F...then finish off with storm collar

 

[bokehman]

I'd put a proper flue cap on, sealed with HT silicone, then a storm collar, also sealed.

OK! But I need to know what I am looking for. It's not as if I could go into a shop here and say "flue cap" or "storm collar" and have someone know what I was talking about. Is there any chance you could post a link to a picture? Thanks.

 

[Hogwildz]

Heres a storm collar. Not sure what size pipe your using, I used a photos of a 6" collar.
(broken link removed)

 

[Hogwildz]

I think what BeGreen was referring to in the way of flue cap is a metal cap that would cover the entire area of concrete with flanges wrapping down the four sides a few inches. It would have a hole in it for the pipe to come through, and the hole would have a raised lip anywhere from 1/2" to a couple inches high. The storm collar would then seal around the pipe above the flue cap lip. IN your case, it would prolly have to be custom made by a sheet metal shop. I think you could try and get away with the storm collar alone, and caulking around the pipe where it meets the concrete. If water does end up coming in the concrete, then you could have the flue cap fabricated & installed.

 

[bokehman]

OK, thanks for the advice. I'll try getting the silicone and the flange. Luckily it doesn't rain much here. We have just had two days of rain but before that last time it rained or was cloudy was the start of May.