CAUSES OF SETTLEMENT
The causes of foundation settlement are
rarely due to the design (or under-design) of
the structure itself. More commonly, damage
is caused as changes occur within the
foundation soils that surround and support
the structure.
The following briefly describes a few of the
more common causes of foundation
settlement:
1-Weak Bearing Soils
• Some soils are simply not capable of supporting the
weight or bearing pressure exerted by a building's
foundation. As a result, the footings press or sink into
the soft soils, similar in theory to how a person
standing in the mud sinks into soft, wet clay.
• In such cases, footings may be designed to spread the
load over the weak soils, thereby reducing potential
foundation settlement. However, the majority of
settlement problems caused by weak bearing soils
occur in residential construction, where the footings
are designed based upon general guidelines and not
site-specific soil information.
2-Poor Compaction
• Placement of fill soils is common practice in the
development of both commercial and residential
subdivisions.
• In general, before a foundation can be constructed on a
plot, hilltops are cut down and valleys are filled in
order to create buildable lots. Properly placed and
compacted fill soils can provide adequate support for
foundations, and are sometimes brought in from offsite locations.
• When fill soils are not adequately compacted, they can
compress under a foundation load resulting in
settlement of the structure.
3-Changes in Moisture Content
• Extreme changes in moisture content within foundation soils can
result in damaging settlement. Excess moisture can saturate
foundation soils, which often leads to softening or weakening of
clays and silts. The reduced ability of the soil to support the load
results in foundation settlement. Increased moisture within
foundation soils is often a consequence of poor surface drainage
around the structure, leaks in water lines or plumbing, or a raised
groundwater table.
• Soils with high clay contents also have a tendency to shrink with
loss of moisture. As clay soils dry out, they shrink or contract,
resulting in a general decrease in soil volume.
• Therefore, settlement damage is often observed in a structure
supported on dried-out soil. Drying of foundation soils is commonly
caused by extensive drought-like conditions, maturing trees and
vegetation and leaking subfloor heating, ventilation, and air
conditioning (HVAC) systems.
4-Maturing Trees and Vegetation
• Maturing trees, bushes and other vegetation in close proximity to a
home or building are a common cause of settlement. As trees and
other vegetation mature, their demand for water also grows.
• The root systems continually expand and can draw moisture from
the soil beneath the foundation. Again, clay-rich soils shrink as they
lose moisture, resulting in settlement of overlying structures. Many
home and building owners often state that they did not have a
settlement problem until decades after the structure was built.
• This time frame coincides with the maturation and growth of the
trees and vegetation.
• Foundations closer to the surface are more often affected by soil
dehydration due to tree roots than are deep, basement level
foundations. As a general rule, the diameter of a tree's root system
is at least as large as the tree's canopy.
5-Soil Consolidation
• Consolidation occurs when the weight of a structure or
newly-placed fill soils compress lower, weak clayey
soils. The applied load forces water out of the clay
soils, allowing the individual soil particles to become
more densely spaced.
• Consolidation results in downward movement or
settlement of overlying structures. Settlement caused
by consolidation of foundation soils may take weeks,
months, or years to be considered "complete."
• As this occurs, the foundation will experience
downward movement -- sometimes at an uneven rate.
This leads to cracks and structural damage.
Foundation Underpinning and Piering
There are two methods used to support sinking foundations:
1-Foundation Push Piers and
2-Foundation Helical Piers.
Foundation Push Piers
The Foundation Supportworks Push Pier System permanently
stabilizes your home's foundation and offers the best opportunity
to lift your home back to level without the expense and disruption
of a full foundation replacement. If you've detected cracks, uneven
floors, jamming doors or windows that stick, then you may be
witnessing the signs of the settling foundation. Contact a local
Foundation Supportworks expert to ensure that you utilize the
easiest and least invasive means of repairing your settling
foundation.
Foundation Supportworks Push Pier systems utilize
high-strength steel pier sections that are hydraulically
driven through heavy-duty steel foundation brackets to
reach deep down to competent load-bearing strata.
The piers have the ability to reach far below the
problem soils and do not rely on friction for capacity.
Used in both residential and commercial applications,
pier installation can be completed year-round without
the major disruption of other methods. Foundation
Supportworks Push Piers effectively stabilize settling
foundations and provide the best opportunity to lift
your home back to a level position.
Push Pier Advantages:
• Can be installed year-round
• Piers reach greater depth than other options
• Long life span – galvanized steel is resistant to
corrosion
• Does not require the use of invasive equipment
• In most cases can lift foundation back to level
position
• Restores Property Value
• Push Piers
• Push pier systems are an
easy, economical solution
that will provide you with
a long-lasting result.
• Manufactured with
industrial-strength,
galvanized steel,
Foundation Supportworks
piers have a high
resistance to corrosion
with a 100+ design life in
moderate soil conditions
Push Pier Installation Steps:
Step 1: Footing is exposed and prepared for
the bracket.
Step 2: Foundation Bracket is secured to the
footing.
Step 3: Steel pier sections are hydraulically
driven through the bracket to competent soil
or bedrock.
Step 4: The weight of the home is transferred
through the piers to load bearing strata. Home
is lifted back to
level if possible.
2-Helical Pier Systems
The helical pier systems offered by Foundation
Supportworks can fix your failing foundation
and restore the property value of your home.
If you've noticed interior or exterior wall
cracks, a leaning chimney, or gaps in window
and door frames, you could have a serious
foundation problem.
•
Foundation Supportworks Helical Pier Systems will
permanently stabilize your home's foundation and
provide you an opportunity to lift the structure back
to a level position. Round-shaft helical piers have a
high resistance to buckling and have the torsional
strength to penetrate deep into competent soil unlike
other square-shaft helical alternatives. Another
benefit of helical piers is that they do not use the
weight of the home as resistance during installation,
so they can be used on both heavy and lightly loaded
structures such as sinking stoops, decks, or sunrooms.
• Helical piers are installed by mechanically "screwing"
them into the soil using small construction equipment
or handheld equipment. Once they reach the proper
depth, heavy-duty steel brackets are installed under
the footing.
Helical Piers
Foundation Supportworks helical
piers are able to efficiently
stabilize distressed foundations
by transferring the load of the
structure from unstable soil,
through the piers, to competent
soil strata below.
The Journal of Light Construction
states that compared to
rebuilding a concrete foundation,
installing helical piers is much
faster, usually taking at least a
week or two less than the
alternative.
Helical Pier Advantages:
•
•
•
•
Can be installed year-round
Round shaft has a high resistance to bending
Suitable for both heavy and light loads
Long life span – galvanized steel is resistant to
corrosion
• Doesn't rely on the weight of the structure for
depth and capacity
• In most cases can lift foundation back to level
position
• Restores Property Value
Helical Pier Installation Steps:
Step 1: Footing is exposed and prepared for
the bracket.
Step 2: Round-shaft helical piers are
mechanically advanced into the soil
Step 3: Foundation Bracket is secured to the
footing.
Step 4: The weight of the home is transferred
through the piers to load bearing strata. Home
is lifted back to
level if possible.