Class A SS Through Concrete

[Busdriver320]

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

 

[brenndatomu]

This is above ground outside? Does it need to be "pretty"?

 

[Busdriver320]

This is above ground outside? Does it need to be "pretty"?

Yes, it is about 3 feet above ground level. The outside is red brick . Doesn't have to be pretty, I can cover it with a escutcheon.

 

[brenndatomu]

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

 

[Busdriver320]

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

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

 

[Karl_northwind]

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.

 

[Busdriver320]

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.

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?

 

[kuribo]

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.

 

[Master sweep walt]

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

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

 

[lost in the woods]

maybe you could go with this (broken link removed) 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

 

[Busdriver320]

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.

Half an inch seems like a lot of caulk. I'm thinking maybe use some fire block expansion foam?

 

[Busdriver320]

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

Hi Walt,
I couldn't find the product name in a Google search (but I have been called amoral before LOL).
Thanks for the reply.

 

[Busdriver320]

maybe you could go with this (broken link removed) 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

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.

 

[kuribo]

Half an inch seems like a lot of caulk. I'm thinking maybe use some fire block expansion foam?

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....

 

[Karl_northwind]

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?

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.

 

[arbutus]

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.

The thimble would be a great option. Consider having an HVAC sheet metal shop make you a custom one if needed.

 

[Busdriver320]

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.

 

[brenndatomu]

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

 

[GENECOP]

Rutland makes a high temp tube a caulk, tape off pipe and wall, lay in, remove tape, nice and neat..

 

[Busdriver320]

I used BOSS® 813 Expanding Firestop Foam and taped the pipe then cut the excess off with a knife. Very clean air tight finish.

http://www.accumetricinc.com/boss/BOSS-Product-Catalog.asp?productID=137