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Correcting Foundation Repair Mis-information Here are the straight answers to commonly asked residential slab foundation repair questions. This foundation repair information pertains exclusively to dealing with foundation repair situations found in DFW area clay soil. Different soils and foundation types demand different repair methods. There is no magic bullet for repairs all across America. Myth 1) The cable in some widely advertised piling systems prevents upheaval by enabling the lower portion to act as an anchor. The cable system does not bolt to the foundation, leaving the foundation free to float upward during upheaval. In this case, the anchor has been dropped.. but they forgot to connect the line! In reality, it would be a mistake to hold down the foundation, as our expansive soil would simply explode through the floor. Expansive clay is stronger than concrete. Myth 2) The best piling system is one driven to refusal. Manually push a round post into dirt as much as practical, and it can be said to have been "driven to refusal". Hit it with a sledge hammer, and refusal has been redefined to a much greater depth. Steel systems are typically driven to a rock strata, while pressed piling systems are more often, " driven to refusal". Pressed concrete pilings seldom are driven deeper than 25 feet, and more often hit "refusal" at depths of 12-16 feet. Here are actual comparisons of piling depths obtained during two foundation repairs. In each case, steel was used to obtain better depth, with much less stress on the house.
Myth 3) Steel always drives to rock This is truer than the claims for pressed pilings, or "locked pilings". Steel piers are typically 3 inches in diameter at the driving end, while concrete pilings are 6 inches. In each case, the weight of the foundation is the limiting force in attaining drive depth. Steel may not hit rock, but the soil will be very rocky, and the ground material will be extremely compacted at the bottom of the drive. In loose soil, steel will always reach rock, while the forces of skin friction and soil compaction will limit the depth of pressed concrete pilings. For most practical purposes, steel drives substantially deeper than pressed pilings and provides a significantly more stable house leveling platform. Myth 4) Mudjacking is a good low cost way to a foundation Seldom does mudjacking give results that are satisfactory for the long run. Sometimes, mudjacking is even destructive to the house. Most companies only resort to mudjacking as a last resort for very poorly built foundations and will obtain a damage waiver prior to beginning repairs. Myth 5 ) The void under the foundation should always be filled after the house has been lifted. Foundation repair companies will seldom fill the void, to allow for normal soil expansion during wet periods. When a void is filled, the expansive clay has no where to go except up through the floor. Once again, expansive wet clay soil is stronger than the typical slab foundation. Myth 6) In pressed piling systems, cable is superior as it is stronger than steel bar. Pressed pilings are a system of 12 inch long concrete cylinders stacked in compression. Truth is that cable seldom offers any material benefit over steel. As one engineer put it.. how strong does a rope have to be when all that you do is to push on it? Myth 7) The system has got to be good as it is patented and sold by more than one company. In 2004 a local television station reported on one foundation repair company conglomerate that appears to sell the same product using several "competing" corporate sales forces. Myth 8) Steel piers and pressed pilings might be installed crooked, leaving the house unstable. During the piling driving process, the soil forms a rigid wall, constraining each section of pipe or concrete to follow the next straight down to refusal. Neither steel or concrete is driven in a crooked manner by a competent installation team. Just ask your engineer.
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