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Frequently Asked QuestionsQuestions and Answers about Foundation Repair in Dallas/Fort Worth
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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
DFW metroplex 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; one
of which is 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.
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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 200 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.
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Root Barrier |
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 said 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.
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 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.
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Out-of-level Doors |
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 also reduce the value of a property.
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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 very effective in stopping further settlement
of the foundation, in the area of the piers. It is
important that the piers be designed and placed 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.
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. Prior to writing a compliance letter, the engineer should inspect the work of the foundation repair company while the work is going on. Upon successful completion of the project, 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.
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Poor Drainage |
Absolutely. Poor drainage conditions allow an excessive
amount of water to soak into the soils. This can trigger
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.
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 are not significantly
impacted.
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Proper Drainage |
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).
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Rain gutter downspout installed into a buried drain pipe |
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 to terminate into a buried drain pipe and then discharge the water far away from the house.
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. 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 soak the rest of the yard to keep the soil around the foundation moist.
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 Engineer must complete the
following:
© 2009 GeoDynamics. All rights reserved worldwide. GeoDynamics serves the North Texas area including: Dallas, Fort Worth, Arlington, Southlake, Carrollton, Richardson, Plano, Frisco, Addison, Prosper, Denton, Lewisville, Flower Mound, Garland, Irving, McKinney, Kaufman, Grand Prairie, Mesquite, Rockwell, Rowlett and Wylie. They also serve the Sherman Denison area.
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