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Buyer Beware: Expansive Soil

By Tiffany Raiford

One of the results of increasing population growth and urban sprawl is the lack of residential land for building in many areas of the country. The land that is still available for building may not be ideally suited to build on.

Many families who have had homes built in recent years have awoken to find cracks appearing in their walls, porches and decks pulling away from the home, and areas of the home beginning to sink. More and more homes are being built on "expansive soil"- earth that swells when it rains.

Expansive soils contain minerals like smectitie clays that absorb water. When the soil absorbs water it expands in volume. The more water that is absorbed, the more the volume increases. Expansion of ten per cent or more is typical. As the soil dries out it shrinks. The shrinkage can remove support from buildings and result in damages. Another typical problem of expansive soil is the development of fissures. The fissures allow deep penetration of water that produces a repetitive cycle of expansion and shrinkage that places repetitive stress on buildings causing significant structural damage including cracked foundations, floors and basement walls. If the building begins moving due to the expansion and contraction upper floors can be damaged and porches, sunrooms and decks can begin pulling away from the house.

The American Society of Civil engineers estimates that 1/4 of all homes in the US have some damage caused by expansive soils. Damage due to expansive soil causes greater financial losses to property owners than earthquakes, floods, hurricanes and tornados combined.

Despite the very high level of damage caused by expansive soil many homeowners have never heard of them because damage occurs slowly and is rarely attributed to a specific event.

How can you protect yourself against expansive soil? It is possible to build successfully on expansive soils if the building can be insulated from any soil volume changes that occur or is stable soil moisture content can be maintained. If you are working with a contractor to build a home make sure the soil is tested and request a soil report. Work with an engineer and your builder to build your home in a way that will not change the conditions of the soil and design the home to minimize moisture content changes and plan to insulate the home as much as possible from soil volume changes. For the best results it is important to engage the services of experts.

If you are buying a home, have your realtor check an expansive soils map that shows the geographic distribution of soils containing expandable clay minerals prone to causing damage to home foundations and structures. Check with the realtor for any areas where expansive soils constitute a significant portion of the land or neighborhoods where there is an unusually high occurrence of cracked foundations, walls etc. so you can avoid buying in an area prone to expansive soil problems. Request a soil analysis to identify the type of soil and determine any expansive qualities of the soil. Check the history of homes in the area where you are planning to buy. Ask neighbors if they have had any problems over the past 5-10 years.

Doing your due diligence and checking out the soil quality can save you a lot of money in repairs, time and the expense of extended litigation and ensure your home is on stable ground and structurally sound for the long term.

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