PREVENTING SLAB SETTLING

By Jeff Stewart, CCIM

 Last month set a record for the hottest June in recorded history. It sets the stage for a similar summer as we had in the drought of 2011. This means homeowners need to be proactive in safeguarding their foundations. This is especially true for owners with properties east of I-35 in the black clay.

     Slab foundations are engineered with beams, rebar and post tension cables to perform under great stress, but in the final analysis, they are still ground supported.  While engineered slabs seldom fail, they certainly can settle enough to bind doors and cause unsightly cracks in brick and drywall.  The key to preventing this is to maintain consistent moisture in the soil supporting the exterior beams of the foundation. As a former general contractor and officer of a builder warranty company, I have seen scores of houses with all degrees of settling. Many of the problems could have been largely avoided with some simple maintenance.

     First, the area most prone to settling is generally where the foundation gets direct afternoon sunlight, usually on the southwest area of the home.  If the soil has become so dry that it has pulled away from the slab by a half inch or more, this is a concern. If the gap is significantly wider, air is likely reaching the soil under the perimeter beam.  As the air dries out the ground supporting the slab, settling is likely to occur.  This is especially true in areas with expansive, clay soil.

     The preventative solution is fairly simple.  In extremely dry periods, such as now, place a high-quality soaker hose parallel to the slab, approximately 20-24 inches away from the concrete.  The key is to have the hose barely emit drops of water.  It is imperative not to make the soil a muddy mess.  The goal is to SLOWLY add moisture to the soil.  Do not saturate it.  This may take several days or a week. Absolutely do not put water directly into any gap next to the slab.  Water saturated soil becomes liquid-like and provides no support. This will only worsen the situation. 

     After a few days of adding moisture, it is not surprising to see cracks in brick or drywall close shrink and doors begin to swing freely again. It just requires awareness and a tiny bit of effort.