Concrete Foundation Wall Concerns

49thparallelDecember 21, 2012

We're in the process of building a home in Montana and the contractor underestimated the grade in front of the house, and as a result had to pour an additional two feet of concrete on top of the already poured wall to get the entry to the porch correct. Rebar was put into the previously poured wall before the forms were put back on and the extra 2' was poured. Even though an engineer and inspector approved this, my concern is that water could permeate through the seam. There will be a foot or two of dirt covering the seam. The contractor has also offered to put a water-proof membrane over the seam and doesn't seem to think it will be a problem. I would appreciate any well informed thoughts.

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Cold joints are always susceptible to water leaks. (Though remember, concrete itself is a pretty porous material.)

A self-adhering membrane such as Bituthene 3000 will work fine.

Whatever material is used should be designated for below grade use on concrete walls.

    Bookmark   December 22, 2012 at 9:25AM
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Make sure it is "waterproofing" instead of "dampproofing" and protect it with something before backfilling. Any asphalt product should be "modified" or "rubberized" (like Grace Bituthene) so it will bridge cracks. It helps to use Grace's Water Based Primer on concrete for their self-adhering membranes. I prefer cold spray-on modified asphalt but if the area is small, 2 or 3 coats of a brush on material should work.

    Bookmark   December 22, 2012 at 10:25AM
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Properly waterproofed, as suggested above, and it won't be an issue. Improperly waterproofed, and it will be a constant headache.

    Bookmark   December 22, 2012 at 2:05PM
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