Establishing the need for foundation repair
Optional foundation repair versus required foundation repair
Foundation repair is almost always an optional repair as opposed to a required or necessary repair.
If a foundation has distorted to the extent that the house is not structurally safe and the situation cannot be corrected without repairing the foundation, then foundation is not optional, it is necessary.
Before you decide to repair a foundation, you should make sure you understand the potential benefits and risks of the the repair. Below are several questions you should ask before deciding to repair a foundation.
How much improvement can realistically be expected from underpinning the foundation?
If the damage is not severe, it may be better to make cosmetic repairs to the house and take other appropriate non-structural remediation measures. Underpinning is not normally effective or cost efficient unless the foundation related damage to the house is severe.
Foundation repair contractors may describe what they do as leveling, but no honest contractor will guarantee that underpinning will result in a level foundation. In my experience, it is unusual for a foundation contractor to make the foundation much more level than it was before he commenced his work.
One possible side effect of a typical repair job is that the foundation may develop a bowl shape after a few years. The can happen where the perimeter of foundation is underpinned, can become less level over time as the central non-underpinned area settles during dry periods while the perimeter is not allowed to settle due to the presence of piers or pilings.
Foundation repair contractors also cannot guarantee that the underpinning will prevent future damage to the house. Residual risk of more foundation movement, including movement severe enough to damage the house, can not be entirely eliminated by repairing the foundation.
Is it possible to mitigate changes in soil moisture?
Foundation movement in expansive soil areas is normally driven by changes in moisture regime in the supporting soil. Even if the foundation related damage to the house is severe, underpinning is not likely to be effective in the long run unless the causes of the changes in the moisture regime are removed.
There are several ways homeowners can mitigate the changes in the soil moisture. They include maintaining positive drainage away from the foundation. The normal recommendation is to shape the surface of the ground adjacent to the foundation so that it falls six inches in ten feet as you move away from the foundation.
No water should be allowed to discharge within 5-feet of the foundation. This includes plumbing leaks, air conditioning condensate discharges, and discharges of water from roof gutters.
- Trees, especially hardwoods such as oaks, and large shrubs can remove large amounts of water from the soil leading to excessive foundation settlement, especially at the outside corners of the foundation.
- All ground within five feet of the foundation should have some sort of ground cover to prevent excessive drying. Last, but not least, the ground adjacent to the foundation should be watered when the weather is dry. Unfortunately, the migration of moisture through the soil is one of the least understood aspects of expansive soils.
We know that, in at least some situations, soil moisture migrates from lower soil strata to the soils supporting the foundation. This moisture can become trapped under the slab-on-ground foundation resulting in a center lift distortion mode.
Will the repair process significantly damage the house or foundation?
The short answer is: yes.
The normal contract many foundation repair contractors use clearly states that some damage may result to your home. The damage is usually minor, but it can be severe. I have personally seen drywall cracks in excess of an inch in width that was caused by a foundation repair contractor.
It is possible that the foundation repair contractor will cause structural damage to your foundation.
Is the foundation movement excessive and progressive?
Excessive foundation movement is where the foundation is bending more than an inch for every 360 inches of span. The span is measured from one end of the foundation to the other end.
Progressive foundation movement is where the movement, usually bending, grows over time. To determine if the foundation bending is progressive, the foundation must be monitored against a stable benchmark. The monitoring should last at least six months and possibly as long as two years.
In summary, the decision to underpin or not to underpin a foundation is a judgment based on an understanding of the type and extent of damage judged to be caused by foundation movement, the probable benefits and risks of foundation repair and the costs involved.