What You'll Learn
Why Foundations Fail
- Nonporous backfill. Soils loaded with clay or organic matter hold water like a sponge, increasing the risk of foundation cracks when the soil freezes and expands.
- Rushing the cure. Concrete must cure slowly to reach proper strength (usually 3,000 psi). Keep it damp for at least three days by wrapping it in plastic, misting with water, and other techniques.
- Insufficient compacting. If the slab is poured over crushed stone that hasn't been firmly tamped, it will likely settle or crack.
- Interrupting the pour. A concrete form should be filled in one go. If you stop and come back the next day to finish the work, there will be a "cold joint" between the fresh concrete and yesterday's work, which is likely to crack and leak.