As discussed in the last blog post, foundation movement is usually related to soil movement. The highly plastic clay soils in portions of Texas have caused 100’s of millions of dollars of damage to foundations. In non technical terms, a highly plastic clay is one which expands a lot with an increase in the soil moisture content and then shrinks a lot when it dries. It has been my experience that the worst foundation movement occurs during dry weather, which occurs every summer in north Texas. This dry weather causes the soils to shrink and allows many slab foundations to settle. Fortunately, settlement of a foundation can usually be remedied by installing piers (piers are expensive but are usually very effective in stopping further settlement in the area of the piers).
However, depending on the soil conditions, the opposite can occur when the soils become re-hydrated (either from Mother Nature or homeowner irrigation) and the foundations are heaved upward by the swelling clays. Upheaval can be very difficult to remedy. I have seen some residential slab foundations in Irving and Carrollton (Texas) heave upward 8 to 10 inches and a commercial building slab heave over 12”. Needless to say, this can be catastrophic to the structure. This type of movement creates significant sheetrock cracks, slab cracks, brick cracks, out of level doors and floors, etc. and obviously lowers the value (and livability) of a home and usability of an office building. Foundation upheaval can be a very difficult and expensive problem to remedy.
My next post will discuss an actual case file where a custom home with a well designed slab foundation experienced about 5” of upheaval during the first year.
For more information on foundation movement, visit www.GeoDFW.com