Class A SS Through Concrete

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Busdriver320

New Member
Feb 18, 2016
9
Michigan
New member looking for installation advice.

I have a 9 inch hole in my poured concrete foundation that is 10 inches thick. I want to insert a Class A Stainless Steel DW Chimney pipe through it that is 8 inches wide.

Question: What should I fill the 1/2 inch space between the pipe and the foundation with?

Thanks from SE Michigan

Busdriver


SS_Pipe.jpg
 
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This is above ground outside? Does it need to be "pretty"?
 
When I went through a concrete wall I just filled in with mortar but I had a larger gap to work with. You could stuff the gap full of rockwool (Roxul at Lowes or Home Depot) and then just put a layer of mortar or high temp silicone over it on the outside to seal things up. You probably wouldn't even have to use high temp, regular silicone is rated almost as high as high temp...and those pipes typically barely get warm on the outside
 
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brenndatomu said:
When I went through a concrete wall I just filled in with mortar but I had a larger gap to work with. You could stuff the gap full of rockwool (Roxul at Lowes or Home Depot) and then just put a layer of mortar or high temp silicone over it on the outside to seal things up. You probably wouldn't even have to use high temp, regular silicone is rated almost as high as high temp...and those pipes typically barely get warm on the outside
Click to expand...

I agree. I'm thinking the same thing. I'm just not sure on what's code for this type of install, there isn't much guidance out there.

Thanks for the reply.

Busdriver
 
I'd do rock wool with an inch of mortar inside and out. that way if you ever needed to get it out, you only have small amounts of mortar to remove. better on the outside might be hydraulic cement. it expands slightly when it cures and will make a more water proof seal.
 
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Karl_northwind said:
I'd do rock wool with an inch of mortar inside and out. that way if you ever needed to get it out, you only have small amounts of mortar to remove. better on the outside might be hydraulic cement. it expands slightly when it cures and will make a more water proof seal.
Click to expand...

That sounds like what I'm going to do, I forgot to think about replacement in the future. Are there any issues with mortar in contact with steel regarding corrosion?
 
I wouldn't use morter-most likely it will crack at some point, especially if there is any movement in the flue. I would go with the rock wool filler and then silicon caulk on inside and outside.
 
Busdriver320 said:
New member looking for installation advice.

I have a 9 inch hole in my poured concrete foundation that is 10 inches thick. I want to insert a Class A Stainless Steel DW Chimney pipe through it that is 8 inches wide.

Question: What should I fill the 1/2 inch space between the pipe and the foundation with?

Thanks from SE Michigan

Busdriver

View attachment 175216
Click to expand...
There is a product called amoral that is completely waterproof to go over the outside of rock wall which would allow for expansion which would be very minor
 
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kuribo said:
I wouldn't use morter-most likely it will crack at some point, especially if there is any movement in the flue. I would go with the rock wool filler and then silicon caulk on inside and outside.
Click to expand...

Half an inch seems like a lot of caulk. I'm thinking maybe use some fire block expansion foam?
 
lost in the woods said:
maybe you could go with this http://www.ventingpipe.com/duravent...himney-pipe-double-wall-wall-thimble/p2476188 you may have to do some alterations to it b/c it is set up for a framed wall. . . . maybe you could just tap-con it in place once you have snipped around to make it fit??? I dunno just a thought
Click to expand...

This was my original plan, but I did not want to core drill such a large hole in my foundation. I may revisit this thimble and try to modify it for my application. If that doesn't work I will stuff some Rockwool and expansion foam in its place and call it a day.
 
Busdriver320 said:
Half an inch seems like a lot of caulk. I'm thinking maybe use some fire block expansion foam?
Click to expand...

With some rock wool in the gap, you might only need a bead 1/2" wide and 1/4" deep. I have used silicone many times for such a gap without issues....Foam might be fine as well but not sure of the temp rating....
 
Busdriver320 said:
That sounds like what I'm going to do, I forgot to think about replacement in the future. Are there any issues with mortar in contact with steel regarding corrosion?
Click to expand...
remember that outer layer is just a layer of 30 gauge stainless, with no real strength to it. I don't think it would hurt the mortar.
 
Busdriver320 said:
This was my original plan, but I did not want to core drill such a large hole in my foundation. I may revisit this thimble and try to modify it for my application. If that doesn't work I will stuff some Rockwool and expansion foam in its place and call it a day.
Click to expand...
The thimble would be a great option. Consider having an HVAC sheet metal shop make you a custom one if needed.
 
This is where I'm at now. H/D wouldn't sell me a small amount of Rockwool so I used some steam pipe insulation. Now I need some recommendations on caulk to fill the 1/2 inch gap out to flush with the foundation.

Chimney_Passthrough.jpg
 
Silicone caulk.
Or you could wrap the pipe with some aluminum foil and then fill the gap with Mortar. The foil will keep the Mortar from sticking to the pipe, making a mess
 
Rutland makes a high temp tube a caulk, tape off pipe and wall, lay in, remove tape, nice and neat..
 
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