When you suspect the foundation of your house needs repair, you are faced with the decision of which repair methodology is best. There are literally hundreds of foundation repair contractors in the area, each claiming their proprietary product or solution is best. A GeoDynamics engineer can help you sift through the options and choose the best solution for your problem and budget. Give us a call, and let us know how we can help.
In the mean time, the following information might help you
understand more about the
When considering why foundations move, it is important to note that
most slab foundations are not completely rigid.
In other words, if the soils below the foundation move, the foundation
will usually move also. When they move, some slab foundations will
no matter what kind of structure, GEO has you covered.click a type below to learn more...
|residential||apartment||commercial|Tiltingoccurs when the foundation moves uniformly and tilts much as a regular table would if one edge of the table was lifted up. Many times, this type of movement does not cause significant distress in the sheetrock or brick veneer. Differentialmovement occurs when one portion of the foundation moves more than another portion of the foundation. This type of movement is more common than tilting and causes more distress in the sheetrock, brick, doors, etc. than tilting.
Additionally, when a foundation moves, it is in the form of either upheaval or settlement (or both). Upheaval occurs when the clay soils experience expansion and this expansion pushes the foundation upward. This upheaval is usually the result of the clays in the dirt absorbing excess water.
The more common type of foundation movement is settlement. Settlement can be the result of several factors as more fully described in the following paragraph.
Foundation settlement can be caused by numerous factors, some of which are:
- The drying out of the soils around the outer perimeter of the foundation caused by lack of rain.
- The effects of the root structure of mature trees / landscaping near the foundation.
- Inadequate watering of the soil around the foundation during dry weather.
- Loosely compacted fill materials. (Fill material is dirt brought in by the builder to help level a lot prior to constructing a foundation on it.)
Settlement of a foundation that is caused by seasonal factors is especially noticeable during the hot dry summer months. This is the period of time in North Texas when the clay soils can dry out. Sometimes as deep as 10 to 15 feet below ground level, depending upon climate and environmental conditions. The drying of the soils occur because of both evaporation and transpiration (water being removed because of trees and shrubs). As the soils dry, they tend to consolidate; as they consolidate, many times, a slab-on-grade foundation settles. The outer perimeter is more susceptible to the settling because of the factors such as a higher evaporation rate and proximity to the landscaping.
If a foundation settles because of problems with fill materials, it is usually because the fill dirt used by the builder/developer to help level the lot prior to the construction of the foundation was not properly compacted. This loosely compacted dirt consolidates over time as a combined result of gravity, water, and the weight of the structure, causing a foundation to settle. This type of settlement generally occurs in the first few years after construction.
Foundation settlement can usually be remedied by the installation of piers, and under certain limited circumstances by “mudjacking”.
Because the clay soils in the North Texas are known for their expansive, highly plastic characteristics, they tend to expand when the moisture content of the soil increases.
Usually the winter/spring months are wet so during this time the clay soils tend to swell, and this can cause some foundation upheaval, especially around the outer perimeter of a foundation. Foundation movement caused by simple seasonal changes (wet/dry cycles) can certainly cause some cosmetic distress but, when compared to the other types of upheaval, seasonal foundation movement usually causes only relatively minor distress.
However, there are factors other than “normal” seasonal changes that can cause foundation upheaval, which, unfortunately, can result in significant problems. Some of these factors are:
- A slab foundation being initially constructed over dry expansive clay soils.
- Poor to marginal drainage conditions around a foundation.
- Plumbing leaks causing water to soak into the soils below a foundation.
- A slab foundation built over an area where, prior to the construction of the foundation, the soil was “cut” down to help make a lot level.
- A slab being constructed over a formerly heavily wooded area.
It can be somewhat complicated to correct a foundation that has experienced significant upheaval. Because of the complexities, it is highly recommended that the homeowner consult with an independent engineer to determine the best remedy for his or her specific situation.
There are basically two reasons to install piers:
- To stop any further downward movement (settlement) of the foundation – in the area of the piers. Under normal circumstances, a pier will only influence an area within a 7 or so foot radius. In other words, it is possible that the unpiered portions of the foundation may experience settlement/upheaval in the future. This includes settlement caused by seasonal factors, improperly compacted fill materials and settlement caused by trees. Even after a slab is underpinned with post construction piers, the entire slab will still be susceptible to upward movement (upheaval of the soils) and/or settlement in the unpiered areas. This means that the foundation may heave upward off of the newly installed piers. It is important to note that most, if not all, foundation repair contractors will warrant their work for settlement only – not upheaval.
- To help bring portions of the foundation to a more “level” position – in the area where the piers were installed.
Generally speaking, when an engineer designs a pier, he considers several factors, including the characteristics of the region’s soil (i.e., how deep is it to “bedrock”, how expansive the clay soils are, etc.). If piers are installed under a foundation, it is important that the piers be installed deep enough so they are founded in a stable bearing strata. Without site-specific soil data (which is very expensive to obtain), it is usually not possible to be precise where "bed rock" is located. This is one reason why it is important to choose an experienced engineer who is familiar with the soils in the neighborhood.
If a properly designed pier is founded in a stable strata, then the foundation should not experience any further settlement, in the area of the pier. However, if the pier is based in a bearing strata that is subject to movement, then there is a potential for continued foundation movement since the pier itself may move.
If this latter condition occurs, it usually occurs because the pier is based in the zone where the moisture content of the soil still varies from changes in climatic conditions (i.e., rain, no rain, evaporation, etc.). Therefore, unless a pier is firmly placed in a stable bearing strata, then that pier has the potential to move as the soil expands and/or contracts.
In order to reduce the effects of seasonal foundation movement, it is important for a homeowner to maintain the soil at a constant moisture around the foundation, throughout the year. This is prevention maintain soil moisture with a soaker hose done by ensuring that water will run rapidly away from the foundation during times of excess rain and by adding water to the soil during times of drought.
During the drier times of the year, the soil around the house can be watered by means of a soaker hose or a lawn sprinkler system. If a soaker hose is used, it is recommended that the hose be placed around the outer perimeter of the foundation at a distance of 1 ½ to 2 feet away from the foundation. Of course too much of a good thing can be harmful, so it is important to realize the goal is to maintain the moisture level, not drench the ground around the house.
Another factor is to realize that because of environmental considerations, some sides of a house may not require as much watering as others. For example, evaporation is usually more intense on the south and west sides of a house (unless these areas are shaded and protected from the wind).
One method to both reduce the effects of the foundation movement and help preclude significant upheaval from occurring is to ensure that there is good drainage around the foundation – the surface of the ground should not allow water to pond within 10 feet of the foundation. Another good idea is to make sure all rain gutters have adequate downspouts so the gutters do not overflow during a heavy rain. Furthermore, all downspouts should either be installed to drain into in a buried drain pipe that will deposit the runoff water well away from the foundation, or positioned such that the water is deposited several feet (10’ or so) away from the foundation into an area where the water will drain rapidly away from the foundation.
Finally, where possible, the ground surface (including flowerbeds) should be sloped at a minimum rate of 5% (i.e. 6 inch drop over a 10 feet distance) away from the foundation for the first 5 feet all around the foundation. At this point (5 feet from the foundation) the ground surface should slope adequately to drain the surface water away from the house. Again, do not allow water to pond within 10 feet of the foundation. Drainage swales should, if possible, have longitudinal slopes of at least 2% (i.e. 6 inches over a 25 foot distance) or a 1% minimum slope (3 inches over 25 feet).
The following photos show good examples of drainage correction. The photos are compliments of NDS, Inc. (a company that manufactures drainage pipes, catch basins, etc. www.ndspro.com)
call GeoDynamics today: 972-497-9998