subject: What Are Some Of The Causes Of Foundation Distress? [print this page] It is a mystery to many homeowners as to the cause or causes of foundation problems. At the first mention of foundation problems, many think of expensive foundation repair. Well, a little knowledge and simple actions could keep that boogieman at bay. First of all, this discussion is limited to areas where there is a lot of expansive clays in the soils such as is the case in southeast Texas and the greater Houston area. We also will be confining our discussions to single family homes, although other structures such as apartment complexes, condos, townhomes, light commercial structures, etc. may be affected the same way.
Next, let's talk about what makes the soils in our area move so much. The answer is the clays in the soils and how they react to moisture. As the soil dries out, the clays will shrink. (If there is no vegetation on the top of the ground, you may see cracks appearing on the surface of the ground.) When the soil becomes wet, they will rehydrate and the soils will expand. Any structure on top of this ground will rise and fall with the expanding and shrinking soils.
The foundations of most homes in our area are engineered with this movement in mind. In a normal year, between the wet season and the dry season, the perimeter may rise and fall as much as three-quarters an inch relative to the center of the structure. Why does the perimeter move more than the center of the house? The moisture content of the soil under the center of the house is relatively more stable than the moisture content around the perimeter because evaporation affects the soil more at the perimeter than the center. Also when it rains, the soil will rehydrate faster around the perimeter - it will take the water longer to travel to the center to swell the soil at that location.
So What is the Main Cause?
The main cause of foundation movement is the changing moisture content of the soil. If you can control the moisture content of the soil, you can control most of the movement of the foundation.
Trees and their root system: Some very large trees can pull out 200 gallons of water a day! Maybe you don't have trees this large on your property or the property adjacent to yours, but you may have 2 or 3 smaller trees and combined they could be pulling out 50 gallons of water a day. Are you putting those 50 gallons of water back every day? Probably not.
Weather conditions: We are in the middle of a persistent drought that could last into the year 2012. This factor is causing visible damage to many homes in our area. We have had years where flooding has been a big problem and drainage issues were foremost on everyone's mind.
Plumbing problems: Cracked or broken drain lines or fresh water pressurized lines can cause problems not just under the kitchen and bathroom areas but the whole length of the lines as they run out to the perimeter of the house. A dripping hose bib is also a big contributor to foundation problems.
Not having positive drainage away from the house: Do you have an area around your house that doesn't drain and water sits for days after a rain? You should have positive drainage away from you home. That means that the ground should be graded so water will flow away from your home and off your property. There should be 6 inches of fall in the first 10 feet from the edge of your home. If your property ends in 5 feet, you should still have that 6 inch drop in that 5 foot space. If water ponds in one area next to your house, you will have soils that stay wet and will swell and areas that are dry will start to shrink. This will cause differential heaving of your foundation, that's not good.
Other causes: There are many other contributing causes to foundation movement and the problems they bring with them. Some of those issues are gutters & downspout placement, secondary A/C line dripping, and landscaping blocking drainage. The good news is that there are remedies to these issues and most of these remedies are cheaper than expensive foundation piers. An unbiased foundation evaluation can give you the knowledge to make a good business decision.
