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Rick, General Contractor
Category: Home Improvement
Satisfied Customers: 21386
Experience:  Licensed construction supervisor with 35+ yrs. experience.
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Whats the best kind of grout to use in repointing stone walls

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What's the best kind of grout to use in repointing stone walls in a very old house?
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It depends on the type of mortar that was originally used. If lime mortar was used (very soft and light colored) then lime mortar should be used to repoint. The problem is lime mortar takes a very long time to cure. If portland cement mortar was used then Sakrete mortar mix is a good DIY option
Customer: replied 6 years ago.
We're removing as much of the original grout as we can. Considering that, is lime or Sakrete superior? And is there any deterioration of the stone likely with either?
It's not the stone you need to be concerned with. If you have lime mortar it is a breatheable mortar. If you cover it with portland cement mortar (which isn't breatheable) the mortar you can't get to will breakdown and fail potentially destroying the wall. If the mortar is hard then it's probably portland cement. If it is soft and light colored it's probably lime and lime mortar should be used to repoint.
Customer: replied 6 years ago.
Is lime mortar that available? Like where?
There is no ready mix lime mortar. You need to make it from scratch. The ingredients can be had at masonary supply houses. Here is the recipe

Use Type S dry lime, gently cover it completely with water and let it sit (do not stir it) for at least 3 days to make mature lime putty. It will keep for months this way and only mix it with sand and expose it to air when ready to use.
Standard ratio is 1 to 3 (lime putty to sand)

Gauging it (mixing in) with Portland cement can speed up the initial set and makes it easier to tool

mix ratios are variable from 1 to 7 to 21 (cement/lime putty/sand) to 1 to 10 to 30

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