Expert: Jim Hise - 1/29/2008

Question
QUESTION: We live in Collierville, Tn and we have been in our home 4 years. It was built in 1987, we have moderate drainage problems and have noticed horzi=ontal and vertical cracking in our drywalls upstairs, seperation of crown molding, cracking in exterior bricks all the classic signs of foundation problems. We have an estimate for placing stabilislab epoxybar reinforced piers( 17 exterior and 7 interior) $23,000. My question is - Is this the best method of piering for our area or should we consider steel or helical piering? Do these concrete piers exceed 12 feet?Also, What are the consequences of delaying any of this treatment?

ANSWER: Laura,
     Concrete piers are very strong and used extensively in commercial construction. Without soil testing you will be gambling with your money. There is no way to know if they have installed these piers deep enough to set them in soils that are stable. With helical piers the soil strength parameters are tested and observed as the pier is being installed. Instead of guessing that 12' is deep enough, the resistance and installing pressure of the helical pier will tell the operator when the pier has passed through the weaker soils and benched into soil strata that is not affected by moisture changes. Your delay in this process can result in higher pier prices, as steel gets more expensive. There can also be more damage to your structure as the foundation continues to settle. You can go online an buy some "crack monitors"...installed in a few locations around the house ( over the cracks )to tell you if and how the walls are moving. This will tell you if movement has stopped or is continuing. The other type of pier is called a "push pier" or pipe pier. It is simply a heavy duty pipe installed by using the weight of the structure as a force to push against. The heavier the structure, the deeper these piers can penetrate. They work best if they are pushed to bedrock. These piers depend on "skin friction" or the resistance of the surrounding soils to hold them in position. If the structure is only one story I would use the helical pier because the push pier will start lifting the house before it is deep enough. If you have soil test results then you will know how deep the piers need to go and you can use whatever system you like. Be sure to find out if there is a "depth clause" in the bid that addresses the extra costs if the piers go deeper than quoted! These extra costs can add up quickly.
Expect a lifetime warranty against further settlement. You will find additional information on this subject at
www.expertbasementrepair.com and www.foundationrepairnetwork Best of luck,  jim

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QUESTION: Thank you so much for your help. I wanted to add a few pieces of info- We live in Tennessee, 2 story home, built on slab foundation.What exactly is soil testing, our contractor says he does " stabilicrete soil stabilization". It goes on to say after his soil sampling is done, his product is intalled to surround each exterior pier.We also remember him saying that he will know when he hits bedrock when 9k psi is reached, and that the piers are 7.5 " in diameter.So does this mean that we can be confident in how deep these concrete piers reach? Thanks- Laura

Answer
Laura,
     I Googled "stabilicrete soil stabilization" and could not find anything. This may just be a term for a concrete pier. If that's what it is generally these piers have a steel rebar cage set into the bored hole and have concrete poured around them.
I also don't recognize his 9k testing pressure.
     When soil testing is done in our region a soil boring is utilized. Generally a few test holes are bored, usually in the range of 20' to sometimes 50' or more...unless very hard/ stable strata or bedrock is achieved. Soil samples are taken from the soil sampler and the soil is analyzed every 3'of depth. This analysis give a representative soil strength profile.
     I think I would get an engineers opinion of this companies product and test procedure just to be sure. Perhaps some else monitoring this site can be of assistance.
There are also several helical pier companies that have piers which can do the job without soil testing
( which is expensive ) Look for a MacLean-Dixie, A.B.Chance or Ramjack dealer in your area.   jim