New foundation bowed out within 2 months.

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Old 10-18-11, 05:19 AM
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Question New foundation bowed out within 2 months.

New*detached*garage*foundation*bowed*outward on the south wall (28'x40) the 28' is on the N & S, with the garage doors on the north. About 2 months after it was built, we notice that the back wall was out ~1/2" and asked our contractor to look at it, he had the cocrete company out 2 weeks later and it was ~3/4" bowed. Now a month later it's ~1", and we have no solution, and are concerned that if it move much more that the keyed slab floor will drop.
 
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Old 10-18-11, 08:11 AM
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Please post some pictures of the area. It's hard to say much without seeing what's going on but you are correct to be very concerned. That is a fair bit of movement and it seems to be moving very quickly. Definitely not a good sign. Depending on how your garage is constructed no easy fixes come to mind. I would certainly stay on it and do not let more time pass which can make it more difficult to hold the builder accountable.
 
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Old 10-18-11, 02:02 PM
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Some strange things going on there. When they want to move, foundation walls usually bow inward, not outward. Often the result of backfilling and compacting outside the wall without substantial enough building loads applied, or temporary bracing installed. Almost sounds like the contractor might have been in a hurry to get the floor slab in, and over-zealously compacted inside the wall before doing enough exterior backfilling and compaction.

Another thing comes to mind--the bowed wall having southerly exposure means its exterior face is getting more direct sunlight every day, and wants to get longer if warmed enough. If the ends are restrained by enough rebar ties into the north-south walls, it's possible for the concrete wall to bow outward to relieve its "growing pains."

Over the years, I've seen some interesting things happen as a result of concrete and steel members "growing and bowing" when exposed to direct sunlight. Bridge girders whose top flanges are warmed while bottom flanges are kept in shadow by deck forming, are notorious for cambering themselves upward as much as 2" (actual difference in camber I measured, using a stringline on a 110' girder) in the middle during the heat of the day, only to flatten back out at night when things cool down.
 
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Old 10-18-11, 07:58 PM
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Not a husker -

Is the wall "bowing" outward into the garage or "bowing" outward toward the soil (is that side is backfilled?

It sounds like a classic problem with moisture control, saturated soil or some other lateral pressure Could this just be a curb on flat slab or is it a stem wall that stabilized by a floating slab for additional restraint.

Pictures (general not detailed close-ups) would help. Concrete wall or block wall?

Dick
 
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Old 10-19-11, 06:01 AM
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Without knowing we are all just guessing from the OP's one and only post. I'm guessing he has a perimeter wall, block or poured. Inside that they back filled with earth or clean gravel and poured the slab on top. In that case I assume the fill inside is pushing the foundation walls out.
 
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Old 10-19-11, 10:06 AM
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Notahusker mentioned there being a "keyed slab floor," which would indicate a poured concrete wall having a keyway formed into its inside face for the slab.

And outward pressure from the compacted fill under the slab would show itself on all of the walls, not just the southerly-exposed wall. And certainly more likely to be present on the longer walls, instead of a short wall (total deflection being directly proportional to total length).

Still think it's related to the bowed wall experiencing more thermal movement from direct sunlight exposure.
 
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