Yet another repointing fieldstone thread


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Old 09-03-14, 08:16 AM
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Yet another repointing fieldstone thread

I've read a bunch of threads on this forum and others about repointing a fieldstone basement but I still have a few questions. I hope you guys can help me out.

1. The foundation is fieldstone but the exterior is concrete. I suppose that a previous owner did some foundation work. Does this mean that water can't get into the fieldstone, and that I can just slather regular mortar over the fieldstones on the inside?

2. If not, then I need to use lime mortar, correct? But what about the gaps between the stones? My understanding is that lime mortar must be done in relatively thin layers, so how do you fill in the voids?

3. The inside walls look like they've been plastered with concrete, which is now crumbling. But its much worse on the bottom than at the top. I assume that's because the moisture seeps upwards when it rains. (I'm going to get a pump and a dehumidifier so that won't be a problem going forwards). Do I need to replace all the plaster or just the bottom parts where it is crumbling? I'm leaning towards just replacing the part that is crumbling.

Thanks!
 
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Old 09-04-14, 02:47 PM
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If the inside mortar is crumbling, water is already there. It sounds like an attempt was made to correct it from the outside but they didn't quite get it done. I wouldn't do any inside work or buy anything until the outside is done first.
 
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Old 09-06-14, 02:15 PM
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Ok, I did some more digging (literally and figuratively). It looks like the exterior cement is purely decorative. It is only for the expensed part of the foundation. Once I dig down I get fieldstone again. My guess is that the previous owner wanted the look of a nice smooth painted foundation.

So I'm back to what looks like a cement plaster on the interior, and it's crumbling on the bottom. I suppose I should chisel away all the cement plaster and redo it with lime mortar? Or can I leave the cement plaster where it is still good and just chisel out the crumbling stuff and put lime mortar over it?
 
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Old 09-06-14, 02:54 PM
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No, not at all. What I said in my first reply, still stands.

"I wouldn't do any inside work or buy anything until the outside is done first."

You need to seal the foundation from the outside. That comes first.
 
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Old 09-08-14, 01:37 PM
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Ok, I'm confused. Are you advising me to create a vapor barrier on the outside with concrete? That sounds great but it's also expensive.

My understanding is that it's ok for old houses to have fieldstone and lime mortar - that it is quite durable if properly cared for. The only problem comes when you create the vapor barrier on the inside with concrete-based plaster. Then the osmotic pressures can build up and damage the fieldstone. Am I wrong about that?
 
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Old 09-08-14, 02:09 PM
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I've never sealed a fieldstone foundation but we always used a membrane on block & poured foundations. The membrane has to go all the way to the footing & even a few inches below. I'll describe the rest of the process if you think that you might be interested. Most people want an inside solution & there really aren't any.
 
 

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