Drainage is an Issue
Do you ever think about the drainage conditions around your foundation and how they might affect the performance of your foundation? Poor soil grading at repair piers can cause foundation settlement. Prevention of poor drainage allowing water to stand at the foundation is one of the principal concerns of good foundation maintenance and is often overlooked after foundation repair.
Repairs Often Damage Drainage
Foundations are typically repaired using one of two systems to support and lift the foundation on the soil at a depth below the seasonally affected zone. In our area that zone is generally considered to be 10 feet or less. Foundation is typically repaired using press piles that largely rely on skin friction with the soil for support or drilled footings that rely on a combination of skin friction and bearing capacity at the bell bottom. Both of these methods require excavation along the foundation during installation. Once repair is complete these excavated sites should be backfilled by implementing a method to compact the soil and the soil graded to shed water away from the foundation. Failure to properly compact the soil will result in voids such as the one shown in the photo above.
Effects of Poor Drainage
If water is allowed to stand or run along a foundation in our area a couple of things may happen. Soil could be eroded where it supports the foundation if water rushes to the foundation after an extended dry period where there is a gap between the expansive soil and foundation causing permanent settlement. Water standing at the foundation in low spots may also cause local loss of bearing capacity for the foundation allowing the foundation to settle into the soil over time causing permanent settlement. Long term both conditions may result in permanent differential settlement that may damage the structure of the building. Water may also stand over pile or pier locations causing them to lose bearing capacity and fail.
The best practice is to ensure that your contractor compacts the soil during refilling of repair excavations. You should also inspect repair areas around your foundation for 3-6 months and replace soil that has settled until proper drainage conditions can be maintained.