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Active Soils in the Metroplex

The DFW Metroplex has soils that are referred to as expansive or active. This type of soil generally contains clay minerals that expand and contract depending on their moisture content. The Metroplex has extended dry or wet periods that require special homeowner maintenance and precautions. Improper homeowner maintenance can adversely affect the performance and structural integrity of the foundation constructed on active soils.

The following procedures should be used to minimize damage caused by shrinking and swelling of expansive soils:
a. Maintain an even moisture content in the soils around the foundation;
b. Maintain the grading about the foundation;
c. Maintain the landscaping.

Maintenance Guidelines

A. General Information
1. When very hot and dry conditions exist and soil begins to pull away from the foundation, you should act immediately to correct the situation. If you will be away from home during these conditions, you should plan to have someone maintain your lot.
2. Uneven moisture content of the soil surrounding the foundation can cause movement in the foundation. If the moisture content in one area is substantially different from another, differential movement can occur, which can cause the foundation to bend. Although this may not damage the foundation, it may cause signs of distress such as wall and ceiling cracks, tape separations, doors that swing open or closed on their own, window frames out-of-square, and cracks in brick veneer and mortar joints. You should check the soil conditions around the foundation and correct any problems.

B. Final Grade
1. The grading (the slope of the ground) around the foundation must be established to cause water to flow away from the home. Make sure water does not collect or become trapped in localized areas near the foundation. These conditions can cause changes in moisture content that can damage the foundation.
2. The surface water is often directed to disposal areas (such as streets, storm sewers, etc.) by way of drainage channels called swales. Swales are typically a shallow trench or depression formed in the yard. Swales must be maintained and not left to erode or fill.
3. Fences installed over drainage swales must be kept off the ground so water can drain properly. Obstructions in the drainage swale can interrupt proper drainage of water from the lot.

C. Landscaping and Yard Maintenance
1. Maintaining adequate ground cover (such as grass in the lawn and mulch in the planter beds) is essential to maintaining uniform moisture content in the soil. The presence of ground cover minimizes evaporation of moisture. When watering grass, shrubbery, and other plantings, you should use a systematic, uniform manner of watering so soil on all sides of the foundation is kept moist, NOT SATURATED. Just as too little moisture causes soil shrinkage, too much moisture causes swelling. Both conditions can damage a foundation. Areas of soil that do not have ground cover may require additional watering, as they are more susceptible to evaporation, causing an imbalance in soil moisture.
2. Position sprinkler heads so water is directed away from the foundation. Shrubs planted close to the foundation may have to be watered by hand.
3. When landscaping, be sure that flowerbeds do not trap water next to the foundation. Planters and curbs often hold water, causing increased moisture in localized areas. This can cause damage to the foundation. If curbs and planters are installed, drainage holes must be provided to maintain balanced soil moisture around the foundation.

D. Trees and Shrubbery
1. Trees and shrubbery may absorb large amounts of water daily, reducing the moisture in the soil and causing shrinkage. Soil shrinkage near the foundation causes settlement in that area. Soil in areas around trees and shrubbery must be adequately watered to prevent settlement and shrinkage. In extreme drought, areas around trees and shrubbery will need more water.
2. Trees especially can damage the structural integrity of the foundation. Root systems of trees can penetrate the foundation, reduce moisture and cause additional damage to the foundation. Precautionary measure may be needed to prevent trees from adversely affecting the foundation. Homeowner maintenance may include the placement of root shields, which reduce the absorption of moisture from the soil between the shield and the foundation.
3. Prior to planting trees and shrubbery, and if existing tree branches extend over your roof or the root system extends into the foundation, you should contact your Builder or those who are experienced in planting trees and shrubbery to discuss proper maintenance options, including the costs involved. Your county Agricultural Extension Office will be able to suggest appropriate plant life and proper maintenance procedures.

E. Gutters and Downspouts
If the home is equipped with a roof drainage system such as gutters and downspouts, water discharged from the downspouts should be directed to flow a minimum of 5 ft. away from the foundation. Gutters and downspouts are a good investment for homes in active soil areas. When downspout extensions are removed for mowing or other maintenance, they must be returned for proper surface drainage. Rainwater should not be rerouted to flower beds or other areas near the foundation. This can cause localized saturation and uneven moisture, which may damage the foundation.