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Drain Tile & Shallow Foundations

Drain Tile & Shallow Foundations

Often, builders or contractors do not install drain tile systems on structures with shallow foundations (crawlspaces, no basements, or slabs). This can be a mistake. Shallow foundations are very susceptible to movement caused by soils that can expand or contract due to changes in moisture.

Many areas of the country have soils which fit this category. They are frequently called expansive clays. These soils are similar to synthetic sponges. When dry they shrink and when wet, they swell. Imagine what this kind of movement does to your structure. This movement is frequently referred to as settling. It often causes structural cracks in foundations, brickwork, plaster, doors and windows that stick, etc. A large majority of this damage can be avoided by simply installing a drain tile system in areas that have this type of soil. The only difference is one added pipe. However, instead of draining water the system will be used to add water.

These expansive clays can be stabilized. As long as the moisture content remains the same, the soils have a tendency not to shrink. Shallow foundation systems are more susceptible to droughts than deep foundations because the footings are closer to the surface. During dry spells or droughts, dry soil can extend 6-8' below the surface.

You can check with your county agricultural office to see if the soil in your area shrinks or swells in response to moisture changes.

The trick to stabilizing the soil is to keep it moist in periods of dry weather. The foundation drain system can easily accomplish this as long as you add a "T" fitting to the system at some point and extend a pipe to the surface. Place a removable cap on the end of this pipe. In dry weather, put a garden hose in the pipe and turn the faucet on low. Let the hose run over night once a week until the dry spell is over. This simple technique will stabilize your foundation for years to come.

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