- Why does the Dallas/Fort Worth area have so many homes that have foundation problems?
- Is it true that trees can cause a foundation to settle?
- What is meant by “seasonal” foundation movement?
- When is foundation movement considered to be severe enough to warrant repairs to the foundation?
- How does installing piers help my foundation?
- I am not familiar with construction techniques. How do I know the foundation repair contractor is repairing my foundation in accordance with the engineer’s specifications?
- Can poor drainage conditions around a foundation cause my foundation to move?
- Will adding rain gutters help control foundation movement?
- Will installing a sprinkler system help control foundation movement?
- What does it mean to be a professional engineer?
Why does the Dallas/Fort Worth area have so many homes that have foundation problems?
Most of the foundation movement in the metroplex area is the result of the foundation responding to variations in moisture content of the soil. The soils in most of the North Texas and certainly the DFW area have a high clay content. As such, when the expansive clays absorb moisture, they tend to swell. Likewise, when they dry, they tend to shrink. This repeated shrink/swell action many times causes a foundation to move up and down.
However, there are several other reasons foundations move that are not related to soil moisture content. For example, when a slab foundation is constructed over loose fill material. (fill material is dirt the builder/developer uses to level the lot prior to the installation of the foundation.) If the fill material dirt was not properly compacted during construction, it will eventually consolidate (settle). When this occurs, a foundation built on top of the fill can settle, also.
Is it true that trees can cause a foundation to settle?
Yes, there has been considerable scientific research done on this subject. Generally speaking, tree roots absorb large quantities of moisture from the soil. Consequently, trees can affect the soil’s moisture content under and around foundations. A large shade tree can transpire as much as 200trees causing problems with foundation gallons of water per day. Trees “transpire” or release water into the air in the form of vapor. The water for transpiration comes from the soil by the way of the roots. This is why trees are known to “pull” water from under a foundation, but only when water in the surrounding soil is inadequate or unavailable.
Basically, if roots are near and/or under a foundation, then the soil in the area of the roots is usually drier than in those areas away from the roots. As the soils dry out, they shrink. This shrinkage sets up the potential for a foundation to settle. However, since water naturally moves through the soil from high-moisture areas to low moisture areas, simply not watering at all can cause foundation problems regardless of nearby trees. Trees can certainly add to the problem, but are usually not the primary cause of moisture loss from the soil.
Having said all that, the usual remedy to a situation where it has been determined that a tree has had a negative impact on a foundation is to either remove the tree or install a root barrier between the tree and the foundation. A root barrier is a ditch that is typically 12" or so wide (the one shown in the photo is 6" wide) approximately 3 to 4 feet deep and has an impenetrable barrier place in it to keep the roots from gaining access to the soil immediately around the foundation. Since the installation of the barrier may cause damage to the tree, it is recommended that the client consult with an Arborist to determine if the tree should be trimmed back before/after the installation of the root barrier.
It should be noted that if a slab foundation is constructed near or over the roots of a mature tree and if the tree is cut down, some unwanted upheaval of the foundation may occur as the soils rehydrate. This situation should be evaluated by an arborist or an experienced engineer.
What is meant by “seasonal” foundation movement?
Seasonal foundation movement occurs as the soils absorb water during times of rain (typically during the winter and spring months) and lose water during times of no rain (typically the dry summer months). Clay-rich soils typically expand as they gain water and shrink as they lose water. This expansion/contraction can cause a foundation to move up and down.
If foundation movement is due only to seasonal weather changes, this can be considered a somewhat “normal” occurrence and typically causes only relatively minor cosmetic damage to the sheetrock and/or brick veneer.
In most of these cases, depending upon the soil conditions, a sheetrock crack can grow wider during the dry summer months but then close back up during the wet winter/spring months (or visa versa). It is common for slab foundations to experience some “seasonal” foundation movement in the DFW /North Texas area.
When is foundation movement considered to be severe enough to warrant repairs to the foundation?
Foundation repairs are usually needed when the livability of a residence is impacted. Examples of this include excessive floor slopes, large cracks in the sheetrock walls, doors become difficult to operate, etc. Also, all of these factors can reduce the value of a property.
How does installing piers help my foundation?
The installation of piers under a foundation increases the rigidity of the foundation and helps it to withstand the movements of the soil. Properly designed & installed piers are veryfoundation piers effective in stopping further settlement of the foundation, in the area of the piers. It is important that the piers be designed by an experienced engineer who understands the soil conditions of the area.
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.)
- To help bring portions of the foundation to a more “level” position – in the area where the piers were installed.
I am not familiar with construction techniques. How do I know the foundation repair contractor is repairing my foundation in accordance with the engineer’s specifications?
It is highly advisable to have the work of a repair contractor inspected by an independent engineer to insure compliance with the design drawings and specifications. This includes inspecting the work during the installation of the repair plan, and after the repair is completed. At that point, the engineer should write a letter to the homeowner that confirms that the repair contractor complied with the design specifications.
In fact, if the residence is either being purchased or re-financed, many lending institutions require that an engineer provide such a compliance letter. At GeoDynamics, we are always willing to ensure that the foundation repairs are being done in compliance with our engineering design requirements. There is an additional charge for this service.
Can poor drainage conditions around a foundation cause my foundation to move?
Absolutely. Poor drainage conditions allow an excessive amount of water to soak into the soils. This can trigger an expansion of the clays (how much expansion is a function of several factors including the soil characteristics and dryness of the clays prior to the absorption of the water). If the clay expands enough, it can cause a foundation to heave upward, sometimes significantly.
Some areas of the DFW metroplex have soil that is very susceptible to moisture expansion (and foundation movement up to 12” has been recorded), while foundations in other areas of the metroplex that have poor to marginal drainage patterns and are not significantly impacted.
It is a generally accepted fact in the DFW area, that to minimize the potential for foundation movement, the homeowner should attempt to keep the moisture content of the soil at a constant rate, year around (i.e., do not allow the soil to get too wet and do not let it get too dry). This usually means that it is important to have drainage conditions around a foundation that will allow the surface water to drain rapidly away from the foundation and then, in time of drought (summer months), not allow the soil to become too dry (this requires watering the soil).
Will adding rain gutters help control foundation movement?
The installation of rain gutters around the roof line will greatly aid in controlling excess water as long as the downspouts are positioned so that they deposit the water several feet away from the foundation. The preferred method of doing this is to install the downspouts so they terminate into a buried drain pipe and then discharge the water far away from the house.
It is estimated that over 700 gallons of water come off a roof of a 1200 sq. ft. house after a 1" rain.
Will installing a sprinkler system help control foundation movement?
A sprinkler system can make it more convenient to keep the soil around a foundation at a constant moisture content. If you are considering installing a water sprinkler system, it is suggested that the water valves be at least 5 feet away from the foundation. Additionally, if feasible, it is a good idea to have a zone designated strictly for the soil around the foundation. This way, during the summer months (or when there has been no rain), it is possible to water the soil around a foundation more evenly and without having to over-water the rest of the yard to keep the soil around the foundation moist.
What does it mean to be a professional engineer?
Professional Engineers in Texas are certified by the Texas Board of Professional Engineers as being qualified to practice engineering in Texas. Once certified by the Board, the engineers may use the designation "Engineer", "Professional Engineer", or "P.E." after their names. Typically in Texas, in order to become a certified Professional Engineer, the candidate must complete the following:
Receive a degree from an accredited college that has an approved engineering curriculum. The curriculum for an engineer must include 8 semester hours of mathematics beyond trigonometry, including differential and integral calculus and 20 semester hours of related engineering sciences. For a structural engineer, this typically includes subjects such as mechanics of materials, thermodynamics, fluid mechanics, structural analysis, etc.
After graduation from an accredited university, have 4 years of active, verifiable experience of engineering work.
At least 3 references from licensed professional engineers. These engineers must have a personal knowledge of the applicant’s character, reputation, general suitability for a license, and engineering experience.
Engineering Firms Engineering firms in Texas can obtain legal engineering status only through the licenses of their own licensed professional engineers who are full-time employees. They cannot obtain a license to practice engineering by using part time employees who are engineers. The registration of the engineering firm gives a company the legal authority to offer the engineers’ services to the public.
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