Repair Exterior Foundation Spalling

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Old 09-16-15, 08:33 AM
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Repair Exterior Foundation Spalling

On my homes exposed concrete foundation, which is approx 20" from ground to siding is deteriorated on the surface, varies about 1/4" to 1" in depth; I believe it is called spalling (?). It is a 1955 home in mid-upstate NY. It appears to have a fair amount of exposed embedded small stone showing in the concrete. I would like to repair this so it is a uniform surface and can be painted or made to look more attractive in some way. I do not know exactly what product to use. I also believe that I would also need to remove any loose pieces, is a pressure washer good to use for this, or is it too aggressive?

Any recommendations are appreciated. Thanks.
 
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Old 09-16-15, 06:44 PM
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Spalling is generally related to moisture migration in the wall and the drying of that moisture to the area of concrete exposed above grade.

A home of your vintage probably had no or limited damp proofing applied to the footer or walls. Even if it was applied, the time element and soil conditions could both have played a role in deteriorating the material used.

It could also be affected by what may have been applied to the interior of the walls. You don't mention any interior finish applications but if they are present, the more vapor impermeable they are, the worse your spalling issue could be. The presence of surface water from grading issues or gutter overflow would also contribute to moisture loading of the foundation and freezing temperatures would bring about the worst of the spalling effect.

There are cements available that are designed to patch surfaces like yours. I might suggest investigating to see what may be readily obtainable in your region. Sto Corporation makes some excellent materials, so that would be one to check out. Edison Coatings is another that is based in CT. I'm sure there are others and other contributors will make their information available.

It is important to understand why the issue has occurred so that you can take appropriate measures to limit or prevent it as much as possible.

Another concern would be that your concrete is not a mix of proper proportions. You could have excessive aggregate for the actual cement used or you could have a mix that was made with cement that was not air entrained.
 
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Old 09-16-15, 08:21 PM
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First, air entrainment is no a cure it all for concrete walls, but it is important in slabs subject to salt and daily freeze/thaw cycles with excess moisture. Is the exposed portion coated with some sort of coating that prevents the concrete from breathing?

The embedded stone particles are just the aggregate that is exposed as result of weathering and not a structural problem. This is not unique since many homes have too much water near the walls due to poor drainage.

A proven method is to completely (and possibly aggressively) cleaning the existing concrete. After that nail some wire mesh to the concrete and apply a thin stucco finish in your choice of color/texture. This improves the wall appearance and separates the wall itself from the existing soil and water, but that is a different thing to attack.

Low cement contact in a mix would be unlikely, because the cement cost is much less than the cost of delivery in 1955 and even much less today.

Dick
 
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Old 09-20-15, 05:46 AM
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'spalling' is usually the result of 2 slabs interaction between themselves as a result of expansion/contraction in reaction to temp changes,,, when temp's hi, slabs expand & they 'rub' against each other causing spalls (damage) as a result of point loading,,, unsealed crks/jnts allow uncompressibles to enter the crk/jnt which contributes to the damage,,, i'd guess your problem is popouts & degradation of lo-strength conc (originally short on ceement in the mix or too much water),,, you could possibly clean the walls & apply thoroseal over some patching cement mix for a pleasing look,,, did that to my father's house in binghamton 25yrs ago & it still looks good
 
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