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Concrete Foundation Expands & Contracts

Q. Can you break a tie for us? We've seen three contractors regarding cracks in our basement. For the most part two of them agree except on one point. It seems to be a basic principal of concrete but they are both adamant they are correct. One says, concrete expands and contracts, the other says it doesn't. Who is correct?

The correct person will probably be the one to fix our basement. We have two vertical cracks 10 feet apart that have been previously epoxied by the builder 8+ years ago. They are slightly leaking again. It's been recommended that we anchor the 10 foot section and flexispan the wall or epoxy it. Company "A" says they'd anchor it in the middle of the 10 foot piece. Company "B" says they would put two anchors (one over each crack). Any advice? The section doesn't appear to have moved much but it is about 1 inch "in" on the inside although seems flush on the outside. We're assuming this section was poured separately and the forms were just moved on the inside.

A. Concrete most definitely moves during expansion and contraction. Just look at our highways with expansion joints between the concrete slabs. These joints get compressed during the hot summer when direct sunlight causes heat and tremendous expansion, and then in the cold winter months the slabs shrink to smaller sizes and the joints widen.

I have concerns about how this affects your foundation issue. Both of your answer sources may be relatively correct. First, concrete does not move substantially when buried below grade because the temperature is relatively constant, as in a cave with a steady 63* F temperature. Foundation concrete expansion & contraction is seldom a source of foundation movement unless subjected to substantial direct sunlight, solar heat gain, and therefore expansion. However, wet soil expands substantially when frozen. Second, I question "what" moved to cause a 1" lateral movement showing as a 1" interior move in a 10' chunk of concrete.

I suspect one of three things happened to move the foundation. Perhaps there was/is a persistent water source outside the 10' concrete section that may have saturated or wetted the soil area, froze and expanded the soil during cold winters, and pushed the foundation laterally toward the inside. Also the concrete foundation may have been broken during construction by an earth moving piece of equipment from backfilling the soil against the foundation too soon after pouring the concrete or insufficient shoring during backfill. Or the third cause might be foundation settling or movement.

My overall message is to address the source and cause of the lateral pressure as well as correcting and supporting the broken foundation. Be certain to address and fix both the problem and the symptom, not just the symptom (crack).

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