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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
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.
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 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.
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
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.
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 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 also 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 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.
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. 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.
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
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.
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). It should be said that for watering
around the foundation to be effective, the moisture
content must be impacted several feet below the surface.
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 to terminate into a buried drain pipe and
then discharge the water far away from the house.
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. If
feasible, it is a good idea to have a zone designated
strictly for 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.
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 Engineer 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 in 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
Registered professional 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 firm gives a company the legal
authority to offer the engineers’ services to the
public.
For a complete description of the requirements involved
with becoming a Professional Engineer in Texas, go to
http://www.tbpe.state.tx.us
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