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Foundation
Repair
When a homeowner in the DFW area suspects the foundation
of his house needs repairing, he is faced with having to
decide which repair methodology is best. Given the
financial investment in the typical Dallas-area home,
the prospect of a foundation repair project of any
magnitude can sometimes be overwhelming. With all the
different technologies available and the myriad of
foundation repair companies in the Dallas/Ft. Worth
area, this important decision is made more difficult.
There are literally hundreds of foundation repair
contractors in the area, each claiming their proprietary
product or solution is best. For most homeowners,
sifting through the options and choosing a solution is a
confusing process; that is, unless they find someone
they can trust who can guide them through the repair
process.
The following foundation repair description might help
you understand more about the causes, repairs, and
prevention of foundation problems.
Foundation Movement
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 tilt and others will move
differentially. Tilting occurs when the foundation moves
uniformly and tilts much as a regular table would if one
edge of the table was lifted up. Differential movement
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.
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
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.
-
The effects of the root structure of mature trees /
landscaping near the foundation.
-
Inadequate watering of 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 the DFW
area 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, 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 can
settle.
Foundation settlement can usually be remedied by the
installation of piers, and under certain circumstances
by “mudjacking”.
Foundation Upheaval
Because the soils in the DFW area are known for their
expansive, highly plastic characteristics, they tend to
expand when the moisture content of the soil increases.
Usually the winter months are wet so the clay soils tend
to swell, 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 caused
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 was initially constructed over dry
clay soils.
Poor to marginal drainage conditions around a
foundation.
Plumbing leaks that cause 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.
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.
What installing piers does
There are basically two reasons to install piers:
1.
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. 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.
2.
To help bring portions of the foundation to a more
“level” position – in the area where the piers were
installed.
About Piers
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.
If a properly designed pier is founded in a stable
strata, then the foundation can 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.
Homeowner Maintenance
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 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).
Drainage Conditions
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 8 to 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 terminated in a buried drain
pipe or positioned such that the water is deposited
several feet (8’ 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. 3 inch drop over a 5 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 8 to 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).
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