What Causes Foundation Damage
You Want to Know What Causes Foundation DamageFoundation damage can occur when the soil expands. Expansive soils contain minerals such as smectite clays that are capable of absorbing water. When they absorb water they increase in volume. The more water they absorb the more their volume increases. Expansions of ten percent or more are not uncommon. This change in volume can exert enough force on a building or other structure to cause damage. Cracked foundations, floors and basement walls are typical types of damage done by swelling soils. Damage to the upper floors of the building can occur when motion in the structure is significant. Expansive soils will also shrink when they dry out. This shrinkage can remove support from buildings or other structures and result in damaging subsidence. Fissures in the soil can also develop. These fissures can facilitate the deep penetration of water when moist conditions or runoff occurs. This produces a cycle of shrinkage and swelling that places repetitive stress on structures.
How Many Buildings are at Risk for Foundation Damage?Expansive soils are present throughout the world and are known in every US state. Every year they cause billions of dollars in damage. The American Society of Civil Engineers estimates that 1/4 of all homes in the United States have some foundation damage caused by expansive soils. In a typical year in the United States they cause a greater financial loss to property owners than earthquakes, floods, hurricanes and tornadoes combined. Even though expansive soils cause enormous amounts of damage most people have never heard of them. This is because their damage is done slowly and can not be attributed to a specific event. The damage done by expansive soils is then attributed to poor construction practices or a misconception that all buildings experience this type of damage as they age.
Expandable, Shrink-Swell, Heavable SoilsExpandable soils are referred to by many names. “Expandable soils”, “expansive clays”, “shrink-swell soils” and “heavable soils” are some of the many names used for these materials.
Why Do These Soils Expand?Soils are composed of a variety of materials, most of which do not expand in the presence of moisture. However, a number of clay minerals are expansive. These include: smectite, bentonite, montmorillonite, beidellite, vermiculite, attapulgite, nontronite, illite and chlorite. There are also some sulfate salts that will expand with changes in temperature. When a soil contains a large amount of expansive minerals it has the potential of significant expansion. When the soil contains very little expansive minerals it has little expansive potential.
Changes in Moisture Content Trigger Foundation DamageWhen expansive soils are present they will generally not cause a problem if their water content remains constant. The situation where greatest damage occurs is when there are significant or repeated moisture content changes.
Expansive Clay Soils:Different soil types have different potential for shrinking and swelling. The more expansive the soil around your home, the more your foundation may by subject to movement. This “Expansive Soil” is the type of soil found throughout North Texas, including Dallas and Fort Worth. Again this is a major factor in foundation damage in the DFW area.
Seasonal Weather Changes:Dry and wet weather cycles, both in summer and winter, produce a soil bed under your home’s foundation that is likely to be shrinking and swelling on a consistent basis. The expansion and contraction of the soil over time can weaken the support for your foundation and cause it to settle and crack. These seasonal changes have a greater impact in the Dallas and Fort Worth areas simply because of the expansive clay soil that covers the North Texas area.
Drainage Issues:Foundation problems can be caused by too much moisture as well as too little. Standing water around your home, large amounts of water dumped by gutter downspouts or a negative slope of the area around your home can cause saturated soil. These issues can be remedied by installing French drains, channel drains, surface drains, swales, retaining walls, and gutters to help alleviate drainage problems around the house.
Trees and Large Shrubs:Trees have extensive tap root systems that extract large amounts of water from the soil. A large tree may drink up to 150 gallons of water per day through its roots. When these roots are under or near your foundation, the drying process may cause a portion of the soil to shrink. The difference in moisture content below the home may cause certain parts of the foundation to shift more than others. A root barrier is highly recommended for any tree located closer than 20 feet to the house. A1 Guaranteed Foundation repair can install root barriers to ease potential foundation issues and to help manage tree root issues after foundation repair is done. This helps prevent any further issues.
Under-Slab Plumbing Leaks:These leaks create excessive moisture in one area under your foundation and may cause that area to heave upward or disturb the stability of your slab. If we think an under-slab plumbing leak is causing the problem, we will provide a plumbing leak test prior to making any recommendations. A1 Guaranteed Foundation Repair provides a post leak test with every foundation repair we perform.
The Bottom Line for a Solid FoundationIt is possible to build successfully and safely on expansive soils if stable moisture content can be maintained or if the building can be insulated from any soil volume change that occurs. The procedure for success is as follows:
- Testing to identify any problems
- Design to minimize moisture content changes and insulate from soil volume changes
- Build in a way that will not change the conditions of the soil
- Maintain a constant moisture environment after construction
- Install Root Barriers
- Expert assistance is needed to do these things successfully.