advise to repair 1800's farmhouse stone foundation

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Old 09-24-06, 05:12 PM
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advise to repair 1800's farmhouse stone foundation

This home has a full basement. At some point the interior surface of the stone basement walls was parged with a thick skim coat of what seems to be plaster. At various areas the plaster coating has detached and the mortar between the bricks is slowly dusting itself towards the floor (Heavy in some spots). It's texture is like a powdery sand.

We need some practical advice as to how best to correct this problem...with materials type and techniques.

Not having faced this type repair before (uncut field stone and laid with 'made of what was on hand' mixed mortar) , we are not quite sure how to proceed. Hopefully, some of you have already dealt with this and know what not to do...
 
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Old 09-24-06, 05:41 PM
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Most likely, the mortar used for the brick was a lime mortar, and at some point later it was parged with a cement stucco. In effect, this trapped moisture behind the stucco and has ruined the lime mortar, causing the portland stucco to fail. The best solution is to remove the cementious parging and to re-tuck the brick (using lime mortar), then re-parge with a lime plaster.
 
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Old 09-24-06, 05:49 PM
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Specifically, you will use type S lime, and washed masonry sand. Take the bagged S lime, place it in a 5 gallon bucket and cover with water. Keep it covered with water for at least 48 hours, and do not stir it. It will keep for years, so long as it has a covering of water. When you are ready to tuck point/stucco, add three parts sand by volume and mix well. Apply to the joints or the wall and keep moist, which in the context of a basement means just leave it alone.

Be careful not to remove too much of the old mortar in one spot at a time; you should repair the joints on a non-adjacent basis. If you want to color the lime stucco, you can use powdered additives or brick dust, which will help increase the set of the stucco.
 
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Old 11-24-06, 06:29 AM
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I'm having the exact same stituation with my basement walls. What problems would I run into if I was to remove the old mortar (which looks close to wet compacted sand covered with a skim coat of plaster/cement) that is in between the stones/rocks and backfilling the voids with a cement that does not contain gravel, mixed to a mortar consistency. Plus, filling in the voids that were created when the wall was originaly built? I'm thinking of doing this in patches, starting at the bottom middle of a wall and working my way out and up in levels. The 1st repair would be in the middle of the wall, make a patch repair, let the repair cure for a few days and alternate on either side of the original repair spot. The second repair would be on the right side of the 1st repair. The 3rd repair would be on the left side of the 1st repair spot. The 4th patch repair would be next to the 2nd repair so on and so on.
Why should I use a mortar and not a cement? The way I figure, The old mortar is garbage and cement could only be an improvement. I've been known to be wrong. By know means am I trying to "cow-boy" this either. I have done repairs in other places and this stuff sets hard so why wouldn't it work for a foundation wall? Thanks for your time.
 
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Old 11-24-06, 04:58 PM
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"Hard" is not the prime requirement for mortar. Read through the thread again, and then I will answer any remaining questions.
 
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