Repointing Stone Foundation - Which Mortar


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Old 07-10-15, 08:42 AM
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Repointing Stone Foundation - Which Mortar

Hello all,

The house was built in 1890 and I have cracks between stone, as well as, falling pieces, with missing mortar.

I've been doing some research on which mortar to use when repointing this stone foundation and I'm a bit confused. Nevertheless, the mortar needs to be lime based. Some people say not to get it with Portland cement at all, while others recommend a small lime, cement, sand ratio. Type S or Type N??

Can I just buy premixed bags such as this one...? Oldcastle 50 lb. Type S Hydrated Mason Lime-65150081 - The Home Depot

Any input is appreciated - thank you.
 
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Old 07-10-15, 08:52 AM
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Old 07-10-15, 09:00 AM
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In my opinion minor tuck pointing can be done with the softest premix you find in a big box store (I think Type N). Extensive tuck pointing or a complete repoint requires a custom mix with minimal Portland Cement and a higher Lime content, which you would need to order from a supplier. Mortar in the 1880-WW2 time frame had Portland in it, just less than modern mixes.
 
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Old 07-10-15, 09:16 AM
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Type N is softer than Type S? I was under the impression that it's the other way around.
 
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Old 07-10-15, 01:26 PM
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M, S, N, O from weakest to strongest.
 
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Old 07-13-15, 06:54 AM
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I think you meant M, S, N, O - strongest to weakest. M = 2,500 psi, O = 350 psi
 
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Old 07-13-15, 06:57 AM
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I'm still a bit torn between N and S, S being a bit stronger with more Portland in the mix.

Does anyone else have any expertise input in this regard? I don't want the stone to crack, so I'm leaning more towards N maybe, softer as eharri3 said.
 
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Old 07-15-15, 09:19 AM
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Thanks, lol... I reversed it by mistake.
 
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Old 07-15-15, 09:22 AM
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I use N on tuckpointing jobs. If you must err with older constriction, err on the side of softer mortar. Better to have to tuckpoint a little sooner than to see bricks or stones degrading.
 
 

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