It’s a fact surprising to many Texas homeowners, but the cause of the damage in an overwhelming majority of the most severely deflected residential foundations is prior, partial foundation repair. One of the few documents outlining the practice of residential foundation evaluations is the 2002 publication of the Texas Section of the American Society of Civil Engineers (ASCE) titled Guidelines for the Evaluation and Repair of Residential Foundations (GERRF). This document addresses partial foundation repair in the following manner:
Underpinning part of a structure may be specified if calculations, tests, or experience show that the unsupported structure can support its design loads. The construction documents should state that underpinning will not improve the performance of the foundation in non-underpinned areas.
“GERRF was a long overdue attempt to bring a degree of accountability to an area of engineering practice which directly affects so many Texas homeowners and yet has historically been without the benefits of peer review,” says Vortex owner and structural engineer Mike Williams, P.E. “Unfortunately, most of the Texas residences which have their foundations underpinned have it done without ever having been inspected by a qualified structural engineer, and most Texas homeowners purchase this procedure without understanding the possible adverse consequences. What GERRF is trying to say about partial foundation repair can be put much more bluntly in layman’s terms.”
Underpinning part of a structure in response to the symptoms of differential foundation movement may have an effect opposite of that which is intended and worsen the damages over time. This diminished slab performance is often in proportion to the efforts taken to level the slab. Leaving a relatively flexible residential slab partly supported on shallow surface soils and partly supported on piles or piers is inherently risky.
“The best thing any homeowner considering foundation repair can do is to have the structure inspected and monitored by a qualified structural engineer over a several year period before installing remedial piers or pilings,” says Mike.
Many homes hurriedly undergo foundation repair as part of a property transfer or in anticipation of putting the house of the market. These repairs are often recommended after a single inspection when symptoms of differential foundation movement are observed in the form of cracks and sticking doors, many of which have been present and remained relatively unchanged for years. Other times the repair recommendations are based on the results of an elevation survey which if repeated over a several year period, might indicate that the foundation is moving very little.
“The decision to perform foundation repair is the responsibility of the owner of the property,” says Mike Williams, P.E. “The job of sharing with my clients the knowledge and experience they need to ultimately make that decision is a responsibility I take very seriously.”
“The best thing any homeowner considering foundation repair can do is to have the structure inspected and monitored by a qualified structural engineer over a several year period before installing remedial piers or pilings.”Mike Williams, P.E.