Problem







Solution
"Terra-firma"


Condor SS, the best foundation insurance money can buy

 

Does Condor SS Work With Piers?

If your home has piers and is still showing seasonal movement, stabilization with Condor SS can most likely greatly improve this situation or eliminate the problem altogether. This is true whether the piers were installed as part of the original construction or installed after foundation problems have been encountered. Since the expansive clay is still expanding and contracting and lifting your home, Condor SS will drive the excess water out of the clay improve the average strength of soil thus enabling your homes piers to work properly. A quality, patented, and guaranteed stabilizer such as Condor SS will ensure your home never moves excessively again. If you are unfamiliar with residential pier failures, just place "foundation pier failed failures" into your favorite web browser and read the stories. It appears that all of the people in the business of remedial foundation repair are quick to point out the problems or failures of "someone else's" way of doing things. Unfortunately, all of them are correct because all of the standard methods have experienced failures.

How Piers Can Fail

Even a pier foundation system requires proper design coupled with either stable soil or rock to work properly. If the soil or rock does not have the required compressive shear strength, the pier will, over time sink, into the ground. Expansive clay soils can also lift a pier if the pier is not properly designed. Although piers are mostly used to provide support against vertical movement, they also provide a degree of support against horizontal movement of the foundation. For a pier that is relying on the strength of clay soil, it is critical that the pier is deep enough to avoid the seasonal variations in moisture of the soil.  It is reported by the U.S. Army Corps of Engineers that the depth of stable moisture content in Central Oklahoma can be as deep as 15 feet. Were your piers installed to that depth or deeper? If not, a pier may perform very well for quite a number of years and yet fail when the soil goes through extreme wet or dry conditions caused by climatic changes or large trees. Knowing the proper depth to avoid significant moisture changes requires the skills of a geotechnical engineer who is knowledgeable of the long-term characteristics of the soil in your specific region.

Many builders assume that if a pier is resting on rock it will remain stable. Unfortunately, not all rock is the same! In Oklahoma, finding a good stable and permanent load bearing rock layer can be quite difficult. Many parts of Oklahoma have thin rock formations consisting primarily of shale or sandstone. While shale or sandstone can have adequate strength properties for pier support, one must be assured that there is an adequate thickness of the rock to be of significance. It is common for the layer of shale or sandstone to be less than one foot in thickness with clay underlying the thin rock formation. The other problem with shale and sandstone is the fact that they can loose significant strength when subjected to excessive water. Of course, the rock thickness and characteristics can only be determined by borings and analysis by a geotechnical engineer. While geotechnical soil borings may be required for larger commercial structures, most of the time such borings are not done for houses or light commercial buildings due to the expense. Therefore, the designer of a pier system who has no soil boring data is merely guessing at the support capabilities of the rock or soil. Is 10 feet deep enough, 20 feet, 40 feet?

While stabilization with Condor SS after a structure has already shifted may not eliminate the need for retroactive underpinning with piers to lift portions of the structure back into place, it does compliment piers by “fixing” what is wrong with the clay soil, thus lessening the forces acting on the piers and foundation. Of course, a hybrid blend of piers and chemical stabilization is the most cost effective, efficient, long lasting and dependable method known. If you value your home or commercial property, you cannot do better than this one-two punch of stabilization. It simply addresses all of the concerns at once.

Residential Piers

Many commercial structures utilize pier designs where the cylindrical drilled pier is widened out (belled) at the bottom of the pier hole. (See drawing to the right) This solves two problems. First, the belled pier has a much larger surface area to provide better support in weak soils. Second, belling the bottom of the hole in clay soils prevents the clay from pushing the pier upwards due to swelling clay along the vertical shaft of the pier. That's right, the clay can actually lift or jack the pier out of the ground. Unfortunately, most light commercial construction and homes with piers do not widen (bell) out the bottom of the drilled pier column. (See drawing to the left) This means that, if the pier column is not resting on stable thick rock or is not deep enough to have a significant portion of the pier in a stable clay moisture zone, the clay can pull the pier vertically or cause the pier to sink. Condor SS can provide stability for your homes piers and in addition, provide the equivalent of a continuous deep pier for your home or building. This is because the Condor SS can completely stabilize the critical zone of clay between the surface and 10-12 feet deep, the zone that would normally be subjected to moisture changes during extreme wet or drought cycles.

 

Post Construction Installation of Driven or Pushed Piers

If a building without piers subsides (sinks) after construction, restorative piering methods are used. Some restorative piers installed after a building construction utilize driven concrete or steel piers. Although many installers use hydraulic means to press the pier into the ground, they would still be considered a driven pier or pile. One problem encountered with post construction driven concrete or steel piers occurs when the clay soil contracts away from the pier.  When the clay soil contracts away from a steel pier, it leaves the steel exposed to moisture and oxygen. This leaves steel piers open to the devastating effects of oxidation or galvanic corrosion, which then causes rust and loss of metal. Of course, most installers of steel piers use large steel posts. The corrosion can eventually result in loss of some strength in the pier but the large quantity of steel present should provide for a long life in most soil conditions. Even those installers that use stainless steel pipe or posts still have the problems of lost support even if they do not corrode away.

Another problem however may manifest itself when the clay dries out and pulls away from the side of the pier. Losing the soil support along the sides of the piers can reduce the original frictional forces that allowed the pier to support the foundation. The loss of support of the soil for the pier can cause the pier to settle. If the pier settles, this can place more stress on the foundation grade beams and also require the piering contractor to come back in to lift the foundation back into place again. Many times the owner may notice foundation cracking in new locations because the foundation had inadequate steel rebar reinforcement to begin with. Condor SS soil stabilizer helps your piers be much more effective by preventing the soil from contracting away from the piers and foundation. Not only that, Condor SS provides the equivalent of a continuous deep pier under your home or building. This provides for improvements in both vertical and lateral stability of the foundation.

The greatest problem with piers installed on existing homes or buildings is the methods used to install the piers. Since the initial installation uses pressure to push the pier into the ground, proper pressures must be used to drive the pier to an adequate depth. To perform properly these "pressed into place" piers must have moisture contents in the soil that will allow pushing the pier to a minimum depth of 20 feet or bedrock without lifting the house. Many times these depths cannot be achieved.

For a more in depth engineering analysis of various post construction pier types, you may want to read the following engineering paper analyzing various underpinning techniques along with their strengths and weaknesses. If you wish, read this non-technical paper from the The Foundation Performance Association on what their committees have found to be problems with all of the standard "fixes" used by foundation contractors.

For the sake of argument, let us assume the pier is installed perfectly and has adequate strength to support the foundation without foundation damage. Possibly it was installed to bedrock. What about the clay that still rests against the foundation and floor slab? When it gets wet, it will still swell. If the remediation contractor installs the piering during dry spells, the swelling clay will merely lift the foundation and floor slab off of the pier. For jacked piers that are bolted to a flange attached to the foundation, the foundation and pier will just be lifted out of the ground. For the pushed pipe or concrete piers that are made up of segments, the piering system cannot restrain any upward vertical movement. Why will the piers not restrain the upward vertical movement? That is because the swelling pressures of many clays greatly exceed the restraining forces of the building weight or pier itself. The swelling clay has even been found to break the large reinforcing bars used in commercial construction with drilled piers!!! This why even large commercial buildings with clay soil beneath the structure have to reinforce the concrete as if it was a self-supporting slab and foundation. For more information go to Sure-Void's website where there is also an excellent video that expains this problem.

If the contractor installs the piering with excess moisture beneath the slab and foundation, when the clay dries, it will shrink. To prevent foundation or slab failure, adequate steel reinforcement must be used. The reinforcement required goes way beyond the standard steel wire mesh, steel rebar, or fiber-reinforced concrete typically used. Even post-tensioned slabs unless properly designed and installed will fail.

The Bottom Line

All of this discussion above should point out the shortcomings of most remedial methods. So instead, why not fix the actual problem; expansive clay soil.

Treating the clay soil with Condor SS and reducing the foundation movement to acceptable amounts in the long run will provide a permanent solution.

Call us today at 918-744-7198 and we will show you how cost effective Condor SS treatment is compared to other failure prone solutions.