Many people think that once you have foundation piers installed, you are done and you can forget about having to do any maintenance in the future on your foundation. Well, that is not really true. I have gone on many, many foundation inspections on homes that have had expensive foundation piers installed but after a few years, their foundation is showing signs again of movement.
The problem will usually fall into one of three different groups.
First, if you do not address the cause or causes of the initial foundation movement when you have piers installed, what caused the movement in the first place will probably continue to cause the foundation to move, even after piers are installed. The home’s foundation is a massive structure of concrete and rebar. Piers are like pencils holding up a desk. Now pencils will hold up a desk and piers will level a slab. My point is, don’t you think whatever caused that massive slab to move can also move those piers? The answer is – yes. It might take a few years, but whatever moved that slab can also move piers. That is why it is so important to address the causes of the movement. That movement could be caused by the drought, a plumbing leak, not having positive drainage away from the structure, etc., etc. There are about a dozen common causes of foundation distress and if they are not addressed, you may be just throwing your money away by only just installing foundation piers.
Secondly, piers need to be installed deep enough and many piers are not. The base area of the pier has a certain amount of capacity it can support but a large amount of its support comes from skin friction. There is also a layer of soil that is ‘active’. That means the moisture content of the soil changes over time and we have very expansive soils in this part of Texas. (Our soils will contract or shrink when they dry out and they will expand or swell when they re-hydrate.) You need to go into the non-active layer of soil to the same depth as you have depth of active soil. So, for example, if the active layer goes down to 10 feet, you need to go down to a depth of at least 20 feet with your piers. This way the skin friction in the non-active layer will anchor your pier so the active layer will not move your pier up or down.
Finally, a new situation may come up and that may affect your foundation even if you have piers installed. As another example large trees can pull out a lot of water from the surrounding area; some very large trees can pull out 200 gallons of water a day! If there was a large tree near your home and it was cut down or it died, where does all that water go that use to be used be the tree? It may not go anyplace. It may stay there and re-hydrate the soils; the re-hydrated soils expand and will lift the foundation up considerably. It can lift the foundation off the piers and now since the loading is off the piers, the piers are more susceptible to moving and failing. Plus the foundation has heaved up causing damage like cracks in the sheetrock, brick, and tile. Doors and windows don’t operate properly. A couple years ago, I looked at one house that moved up about 7 inches which can be devastating to a structure.