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Expansive Soil Causes Foundation Damage

Many homes around the country are build on layers of clay or bentonite soil. Also known as expansive soil, management of the soil’s water content is the key to preventing or halting foundation damage. This issue is particularly evident in Texas, Louisiana, and Oklahoma where expansive clay soils are the dominant soil type.

All foundation types are vulnerable: slab, pier and beam and basements.

There are several things that can go wrong with your basement. The most common reason foundation walls crack, bow, or settle is due to the earth around them, not a poorly constructed foundation. The dynamics of the earth/soil around a home can change due to various weather conditions and time. These changes put a lot of pressure on the concrete and can cause cracks, bowed walls, settling, etc…. Moisture or lack of moisture is the # 1 reason soil conditions change.

expansive soil damageWhen a basement is first constructed, it is typically sitting on soil and is backfilled with the same soils that were extracted from the excavation. At that time, there will be a particular moisture content in the soil based on the weather conditions at that time. Over time, the moisture content in the soils can change from dryer to wetter.

Additionally, the soils used to backfill around the foundation can take years to settle to a fully compacted state. In some cases, the soil can settle enough around a foundation to create a negative slope towards the home.

The bottom line: Do everything you can to maintain the soil around your home so the dynamics of the soil do not change and cause stress to your concrete foundation.

Most people blame their faulty foundation on the type of concrete used, lack of re-bars, and just poor craftsmanship on the part of the foundation contractor. Some of this may be true, or partly true, but the soil your home sits on causes the most damage.

When a foundation is built, it typically does not have any cracks at that point. It is generally stable, has not settled, and looks pretty good.

When the condition of the foundation changes, it is generally due to the earth that the foundation is sitting on. The earth, or dirt, will experience many weather related changes. Rain, snow, hot, cold, and then dry. All of these conditions cause the dirt to chemically change, or expand and contract. This can put a lot of pressure on your foundation walls and basement floor when the earth moves.

sump pump in basementIn a perfect situation, you want to keep the soils around your home at a constant moisture content. When it rains a lot and over extending periods of time, you don’t want too much water saturating the soils around your home. Good grading around the home is one of many ways to help this. When we are lacking rain or melting snow, you don’t get enough water in the soils around your home. It is a good idea to water your foundation during excessive dry periods. Keep the soils at a constant moisture content to reduce the problems that they can cause your foundation.

Clay-like soils are a big factor. The more clay in your soil, the more likely your soil will expand and contract based on different moisture contents. Wet clay-like soil will expand. Expanding soils can push against your foundation walls and floor. Dry clay-like soil will contract. Contracting soils can cause your home to settle, or go down. They can also create gaps in the soil next to your home. These gaps can let water run directly down against the foundation the next time the rain comes back.

The best way to avoid foundation problems are to maintain the soils around your home. Here are some things that you can consider:
1. Make sure there is good grade or slope so that rain/snow can effectively drain away from the basement walls.
2. Bury your gutter downspouts and/or sump pump discharge so that this water can effectively drain away from the basement walls.
3. If it becomes dry, water the soils around the basement walls to keep them at a consistent moisture content. Don’t let the soils dry out. A soaker hose works best to get the moisture down to where foundation sits on the footings.
4. If building a new home, have a soils test done. This will tell you how much potential there is for your to experience expansive soils.
5. If building a new home, don’t backfill with the expansive soils.
Do not build on clay like soil. You can do a soils test to see what the soil conditions are. If the soils pose a potential problem, you can inject a chemical into the ground to break down the clay. Another option is to install piers under the footings which can support the home in lieu of the clay soil.
Another way to help is to backfill with gravel. These options cost more up front, but they can cost you a lot more later in foundation repair bills.

Resource:  http://www.gordonenergy.com/blog/foundation-repair-why-foundations-fail/

Living in areas with clay soils can be a serious challenge when is comes to maintaining the integrity of home’s foundation. It just takes paying a little more attention to water management around the home. In some instances, installation of a French drain system may be required. Always check with a reputable foundation repair company.

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