South Bay home buyers and home owners can learn a great deal about dealing with expansive soil issues from the City of Torrance. Several areas within the City of Torrance contain differing amounts of expansive (also called adobe or clay) soil. Expansive soils are naturally occurring materials found in low lying regions and flood plains. In Torrance, such regions are the Walteria Lake area, between South High School and Hawthorne Boulevard and most of North Torrance, north of 190th Street and east of Hawthorne Boulevard. Read some history – CLICK HERE.
Most locations in Torrance originally required fill before housing tracts could be built due to poor drainage which filled with water after the winter rains. At the time of the land filling the developer used proper filling procedures, but soon after problems developed in the area due the expansive nature of the fill. The filling procedure came to be considered improper. The fill contained Adobe soil which is “expansive”.
Expansive soil is subject to swelling and shrinkage, varying in proportion to the amount of moisture present in the soil. As water is initially introduced into the soil an expansion takes place. When dried the soil contracts, sometimes leaving small fissures or cracks in cement or stucco or interior sheet rock. Excessive drying and wetting of the soil progressively deteriorates structures over the years. This excessive wetting and drying causes damage due to differential settlement within buildings and other improvements.
Major problems ensued with walls and chimneys falling down, changes in the angle of flooring, doorways becoming distorted and more. Many homes were in such bad shape that they had to be completely torn down. Since a large area was filled improperly there is little that can be done to solve the issue. Residents however have adjusted to this condition .
If your home or a home you are considering purchasing is located in these areas, it is likely that you will experience more hairline cracks in the walls and slabs than a home built on sandy soil. This is due to the native soil in the area, and not much can be done to prevent minor soil movement. You can, however, protect your house from major damage, and minimize the minor cracking by taking a few precautions to ensure that the soil under the foundation does not become either saturated or completely dried out. The following guidelines are intended to assist you in that regard:
1. Proper drainage after a rain is the most important single factor. Rainfall should run off the property as fast as possible following a storm. Re-grading of the lot and installation of a drainage system may be necessary to alleviate the drainage problem.
2. Installation of rain gutters and downspouts can help in the elimination of a drainage problem, but be sure that the downspout outlet does not discharge close to the structure, as this could cause more of a problem. The discharge point should be on walkways, driveways or other paved areas away from the building. Drainage should then flow directly to the street.
3. In the summer water your lawn lightly two or three times a week. Heavy watering is not recommended as this could saturate the foundations. However, it should be emphasized that a uniform moisture condition around foundations should be maintained throughout the year. This will prevent periodic drying and wetting which will cause damage to structures.
4. Monitor your water consumption. An unexplained increase in your water bill could indicate a plumbing leak. Any leak should be repaired immediately, as the soil around the foundation could become saturated and distressed if the leak is allowed to continue for a long time.
5. If you notice a number of ground fissures or cracks in a short period of time, it would be in your best interest to contact a soil engineer who specializes in expansive soil problems. A soil engineer can investigate the problem and make specific recommendations for elimination of the problem and repair of your home.
6. Planting trees within about ten feet from the house is not recommended. Trees tend to extract moisture from soil causing shrinkage.
Below is a map showing the most impacted areas. Contact the City of Torrance for further information.