What causes foundation failure?
Do you know what makes foundations weaken?
We know what the signs are: cracks in walls and floors; doors and windows that won’t open; stairs that come away from porches; chimneys that separate from the house siding, to list a few.
Houses and commercial buildings usually look very solid. Built with concrete, and beams, it’s hard to imagine what could cause them to crack and shift other than an earth quake.
There are many causes of foundation failure, here are the six main ones.
- Soil type – especially expansive clay soil
- Poorly compacted fill material
- Slope failure, mass wasting
- Poor construction, and
How many of these were you familiar with? We explain a little more about each below.
Soil Type – Expansive Clay Soil
The most common kind of expansive clay can absorb so much water that it can swell by several hundred percent. The pressure from this degree of swelling can easily lift or “heave” most residential homes. Soils expand with moisture and they contract with dessication, causing up and down movements known as differential settlement. To preserve structural integrity of the building, we have to provide underpinning for the foundation.
Poorly Compacted Fill Material
If the fill material on a lot is not sufficiently compacted to support the weight of the structure above it, there will be foundation problems. The problem can be from the mix of odd fill materials, and from poorly compacted fill, or both.
Slope Failure / Mass Wasting
Geologists use the term “mass wasting” to describe the movement of earth downhill. It could be “creep” which is slow, or “landslides” which are sudden. Slope failure as we use it refers to “creep”.
Underpinnings can act as a barrier to “creep”, but the power of gravity is such that unless the underpinnings were specifically designed to stop slope failure, warranties can’t usually cover this in sites exposed to slope failure.
Erosion may be the most straightforward cause of settlement issues. It can come from poor drainage, uncontrolled water flow or lack of ground cover. If not identified early, erosion can wear away the soil around foundations, creating a new need for underpinning.
Most towns and cities now have building codes that require soil testing and engineer certification before and during the building process, so poor construction is less and less the cause of foundation failure.
We all know what perspiration is, but transpiration is a less commonly known word. It is the word that describes plants removing moisture from the soil. Trees withdrawing moisture from the soil in the summer can accelerate soil shrinkage in hot summer months. It is the expansion and shrinking or contraction of soils that disturb the foundation.
A lot is taking place under the soil, often invisible from the surface. So we need to keep our eyes open to any signs of foundation weakness.
We’re Brackett Foundation Repairs in Durham, North Carolina. We have almost 40 years of foundation repair experience. We do foundation repair throughout North Carolina and the United States. Call us at (919) 806-5232. We fixed your neighbor’s home.