Disintegrating Foundation

Old 01-29-08, 09:41 AM
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Disintegrating Foundation

I'm (perhaps foolishly) considering rebuying a house I sold several years ago to which I'm emotionally attached, but which has "spawling" in the basement -- worse now than when I sold. Essentially, water permeates, and the walls are actually disintegrating; fine sand can be swept up from the floor where it falls, leaving behind rocks in the foundation. I also notice worrisome cracks in the plaster upstairs where, previously, there were none. How serious a problem is this, what's the likely fix, and how fast should I run, haha??? Would just shoring up the walls with foundation piers solve the problem or is this a foundation that must eventually be replaced? Can't see where or why water would be a partiular issue (it's on a hill, so no run-off; gutters are open and downspouts diverted from the house). I believe this is just a case of subgrade materials being used on-site by the owner/builder before there were building standards; the water is "normal," but the foundation itself wasn't built to last. If it's a $20k dig-up-the-lawn proposition, obviously this will affect my offer (backed up by a structural engineer) or I may just walk altogether, much as I love the house. Any input is welcome.
Old 02-09-08, 06:50 PM
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Since no one has responded I will try. First off I am not a pro, but I have a similar situation and have done exhaustive research. Spalling is usually caused by a combination of alkali soil and groundwater leaching through the concrete. Nothing you can do about the alkali, but if the wall is still structurally sound (you might want to get an engineer), you can waterproof well from the outside (install a waterprooof membranes system) and install weeping tiles. This will keep the water from leaching through and should stop the concrete from breaking down or at least slow it. Don't know what the cost would be there, but here in western Canada, I would be looking at probably $20,000 to do this, although I have been told it is a cheap and easy, if heavy do-it yourself job. If the concrete is not sound (it sounds like it might not be if you have cracks as well and plaster cracking upstairs), you are kind of stuck. You can try having it propped up in various ways (e.g concrete knee walls, new foundation inside the old), but then you still need to waterprooof. Probably the best solution in this case is to lift the house and repour the foundation, which I have heard is not quite so bad as it sounds. It would cost around $45,000 around here, but you end up with all the latest innovations and an easily developed basement. Be sure to contact a house moving company, as they have the most expertise and make sure they are insured in case they drop your house Hope this helps and if anyone sees innacuracies in what I have said, please correct them.

Now that I read more carefully, it sounds like maybe you don't have a concrete basemsnet. All of what I said above assumes you have a concrete foundation. If it is field stone with mortar, and it is simply the mortar falling out, and if you catch it soon enough, you can simply repoint the mortar and seal from outside as described above. Again the cracks suggest the foundation might be compromised, but maybe not.

The seriousness of the cracks upstairs depends on where they are, how quickly they apear or change and how old the house is (i.e. is it still settling or should that have stopped by now). Again, an engineer would be worth the cost, especially if it save you thousands on the house.
Old 02-10-08, 07:45 AM
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i am a pro,,,

& spalling is caused by 2 slabs 'grinding' each against other from thermal contraction/expansion, jnt edge breakage (aris), or just normal traffic wearing conc's soft spots,,, the rec'd repair's cut, chip, & replace w/polymer-modified cement mortar.

soil acids can attack the lime in conc's cement leading to degradation of the conc,,, its not uncommon when the conc was lo-stregnth or not properly consolidated when placed,,, same fix for that, too.

the exterior systems's probably the best suggestions but that may place the property out of reach,,, crks can be injected w/hydrophyllic polyurethane's to seal against wtr leaks,,, addl supports may be needed to support the house, too.

all this being said, the previous post is excellent from a non-pro,,, well-done.
Old 02-10-08, 02:50 PM
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In order for someone to advise you as to what should be done and or how much cost would be, you need to post how big the foundation is. And if it is a full foundation or not. If house is quite small sureing it up with beams and replacing foundation may not be out of question.

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