# Proper cement used for chimney repair?



## Henry G (Jul 9, 2010)

I've gotten some conflicting advice on which cement to use on an old chimney. I was told that I cannot use just any motar mix for chimney repair because I have an older chimney. In my current house I'd like to redo some of the exterior parts of the chimney above the roof, but in the house I'll be moving into at the end of the summer I have some repairs I'd like to do on the chimney that is inside the house (attic, etc). I have cement needed to repair anything in the firebox, but it didn't say anything about exterior use, or outside the firebox area. 

 This is what I bought, but have yet to use...







Type S Mortar Mix

 Any thoughts?


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## EatenByLimestone (Jul 9, 2010)

I used type S to build a chimney, but they might be referring to a lime mix of cement.  I really don't know when they moved away from those mixes.  How old is the chimney?

Matt


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## Smokey Bear (Jul 9, 2010)

The mix you have should be fine for an exterior repair, you only need special cement in the firebox/smoke chamber area of a fireplace.


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## EatenByLimestone (Jul 10, 2010)

I used refractory cement for the terra cotta liner.


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## Yagminas Masonry and Wood-heat (Jul 10, 2010)

Generally you want to use a cement that is "softer" than what you are laying. Type "s" is used mainly for block and sometimes stone. Type"n" is better suited for brick. For soft clay brick, lime mortar is best. When laying the old soft clay brick, it is necessary to soak the brick in pails of water before they are laid. Even better to work on an overcast/drizzle type day....


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## Henry G (Jul 12, 2010)

EatenByLimestone said:
			
		

> I used type S to build a chimney, but they might be referring to a lime mix of cement.  I really don't know when they moved away from those mixes.  How old is the chimney?
> 
> Matt



 I would assume the brick is as old as the house.. so 1915-1920 era. 

 Does it matter if this repair will be exposed to the elements or not?


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## Henry G (Jul 12, 2010)

Smokey Bear said:
			
		

> The mix you have should be fine for an exterior repair, you only need special cement in the firebox/smoke chamber area of a fireplace.



 For the firebox, I bought something called Heat Stop.

http://www.heatstoprefractorymortar.com/


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## EatenByLimestone (Jul 12, 2010)

I wouldn't think it would matter inside or outside.  I think it has to do with the brick type more than internal or external application.  I'm not a mason so I really couldn't tell you for sure.  

Hopefully the mason from above comes back.

Matt


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## Henry G (Jul 12, 2010)

Well if this Type S is the wrong kind, and I can't bring it back, is there anyway to turn this into type N?


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## EatenByLimestone (Jul 12, 2010)

Why can't you bring it back?  It's only a few dollars, use it to fill a crack in the basement.  

Matt


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## Yagminas Masonry and Wood-heat (Jul 13, 2010)

Yeah, go ahead and use it. It's not life or death. I've been stuck more than once and as long as you are not sloppy it'll be a fine job. If it is sloppy, let it set up for a day or two, soak the hell outta the area and brush some muriatic/hydrochloric acid on it( wear a mask and rubber gloves and boots and stuff...) scrub and rinse. Repeat if necessary...RINSE WELL....rinse some more.

Kev


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## Henry G (Jul 13, 2010)

What is the purpose of the muriatic/hydrochloric acid?


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## Yagminas Masonry and Wood-heat (Jul 13, 2010)

The acid is really effective in removing mortar stains.


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## Henry G (Jul 22, 2010)

How thick should the motar be between bricks?


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