Top 3 Causes of Slab Foundation Settlement
Structures settle into the ground for many different
reasons.
The number one reason structures settle
and foundation repair is later needed is because
of poor soil preparation when the structure was
built. The builder fails to prepare the soil before
the concrete is poured.
The soil, once it is graded, no longer remains at
it's NATURAL DENSITY. It is now disturbed, and is
loose and porous. The contractor grades the property
to level out the lot, sometimes cutting into a hill
at one side and filling up the low spots at the
other side. He rarely compacts this soil to it's
natural density when he grades it down. The slab is
poured level, but the homeowner soon sees his
beautiful home start to develop cracks in the brick,
cracks in the sheetrock, and the bathroom tile.
Doors will not shut and some cannot lock. What
happened?
What has happened is that the loose un-compacted soil
compacted on its own, and the slab settled into the
ground. Un-compacted fill dirt will compact when it gets
dry or when it gets wet, bringing the structure down
with it. Once a Bedrock foundation repair specialist
installs supports deeper into the ground to reach
undisturbed soil, soil that is naturally compacted
at it's natural density, it is then strong enough to
support most structures. On loose soil that is
un-compacted, even a light small shed will soon
settle.
Some sub-contractors may have water and moisture
inside their trenches before the concrete is poured,
and they pour the concrete anyway. It looks good at
the time, and they didn't have to spend any time and
money digging the wet muddy soil out of their
trenches. No damage is done until the new homeowner
starts to see cracks and damage. The homeowner is
faced with an unforeseen foundation repair expense,
as well as interior damages and landscape damage.
The soil again was not prepared properly before the
concrete was poured.
SOLUTIONS - How to prevent
foundation problems before construction of your new
home or building:
A foundation/structural engineer and an architect
should be involved in the
building process from the beginning of construction
to protect the future owner.
A foundation/structural engineer can insist on seeing compaction tests
provided by the builder to insure all the soil is
properly compacted before allowing any concrete to
be poured. This should be done before concrete
driveways and sidewalks are poured as well.
The architect should visit the construction site and
prepare plans to construct the home high enough to
insure proper water drainage, and then the
foundation/structural engineer
should be involved to verify that the builder did in
fact follow the architect's plans.
The foundation/structural engineer
can also inspect the trenches for
standing moisture and wet spots, and request that the wet
soil be removed and the area properly compacted
before concrete is installed.
Of course, foundation/structural engineers
and architects charge a fee, but those fees are
much less than future foundation
repair fees, and repairing crack damage fees.
Please call our sister company,
Bedrock Engineering, LLC, for prices on
hiring a Registered Professional
Foundation/Structural Engineer.
The number two reason foundations settle is
because of the plasticity of clay soils. The clay
will swell when it gets wet, and it will shrink when
it dries. This swelling and shrinking will WORK the
weight of the structure down into the ground. Over
time, the foundation will remain more settled than
it has risen, leaving the homeowner with an
unleveled
home and doors that stick.
If the homeowner can maintain the moisture of the
soil under the foundation at a constant level, and
there will be no swelling and shrinking, but during
extreme dry spells that is sometimes impossible.
The homeowner, when undergoing a dry spell, must
first water the foundation according to Bedrock's
rules in our Maintenance Procedures
here, but must also prevent water from ponding around the foundation as well, to prevent
swelling of the soil.
Plasticity is the ability of the soil to shrink and
swell. The higher the plasticity of the soil, the
more apt the soil is to rise up and then settle
down. Some of the highest soil plasticity in the
world is in North Texas. There are also strong clay
soils mixed into most of the southern United States
and the Midwest. One side of your house may have
more clays than the other side, and one neighbor's
foundation may be sitting on more clay than the
other neighbor's, which accounts for some homes
experiencing more foundation problems than others.
The third main reason for foundation settlement is
poor drainage. Water must never pond around a
foundation. The soil around the foundation must
always shed water away from the structure. We always
say, to fix the foundation you must first fix the
drainage.
Water is the enemy. It can wash out around
foundation supports, but it can also cause the clays
to swell and shrink, damaging the foundation. Also,
If there is too much moisture in the soil, it can
reach a saturated point where it will no longer
support the weight above it.
If you think you have a moisture problem under or
around your home, call our sister company,
Bedrock
Drainage Corrections, LLC, and they can design a
drainage correction plan to collect the moisture
and reduce the potential of any future moisture
damage.
Also see:
Common
Architectural Defects in Foundation Construction
-
How Architects
Under-Design Homes
When it's your
foundation, we're the ones to call...
WE DO IT ALL!
