How can marine clay affect my home?
Are all cracks in a house due to marine clay?
How can I be sure my problem is due to marine clay?
What should I do to repair damages caused by marine clay?
Why can't I patch the cracks in the wall?
Will every house built in marine clays have problems?
What can I do to prevent marine clay damage from occurring?
What kind of county assistance is available?
What is marine
clay?
Marine clay is a type of soil found in Fairfax County that contains
clays that swell upon wetting and shrink upon drying. Potential problems
associated with these soils include land slippage and slope instability,
shrinking and swelling of clays, poor foundation support, and poor
drainage.
Where is marine clay found?
Marine clay occurs in an area of Fairfax County known as the
Coastal Plain, an area located primarily east of Interstate 95. For
specific information on the location of marine clay in your area, contact
the Northern Virginia Soil and Water Conservation
District at 703-324-1460, TTY 711 or the
Environmental and Site Review Division at 703-324-1575, TTY
711.
How can marine clay affect my home?
Pressures exerted by marine clays upon swelling can crack and
damage below-ground walls and ground floor slabs. Shrinking and swelling
of soils underneath the foundation footing can reduce the bearing
support, damaging foundation walls. Land slippage and slope movement can
also undermine the foundation support and, in some cases, can cause walls
or sections of the house to separate or break apart.
Are all cracks
in a house due to marine clay?
Not every crack in a house will be caused by marine clay. Some
hairline cracks may be due to natural settlement of a house and may not
represent severe structural damage. Settlement of improperly compacted
non-clay fill under a foundation, pressures exerted by water collecting
next to the house, and substandard building construction can also result
in cracks in walls and floor slabs and in foundation damage.
How can I be
sure my problem is due to marine clay?
Weather patterns can provide clues to identify marine clay
damage. For instance, foundations may settle during extended dry periods
which cause the clays to shrink; wet periods may increase swelling
pressures on walls; slope movement typically occurs during wet periods of
the year. Cracks caused by marine clays tend to open and close with
changing moisture conditions. Often, several houses will be affected in
areas which are experiencing marine clay problems. Check to see if any of
your neighbors are experiencing similar problems.
What should I
do to repair damages caused by marine clay?
Most types of structural damage resulting from marine clay can
be repaired. You will need to obtain a building permit before any repair
work is undertaken. The
Fairfax County Code (Chapter 107 -- Problem Soils Ordinance)
currently requires a soil report prepared by a qualified geotechnical
engineer for all new construction and grading work in marine clay areas.
As a matter of practice, an engineering report is required for repair
work, unless the homeowner or contractor prepares adequate
recommendations and plans. Engineering designs should be submitted with
the application for a building permit. When the County approves your
designs, you will receive a building permit. The engineer who prepared
the repair designs must inspect the repair work and certify that the
designs are properly implemented.
Why do I need an engineer?
An inadequate repair can often result in no repair at all --
the damage may resurface after some time. An experienced geotechnical
engineer can help identify the source of the damage and ensure that the
proposed designs adequately address the problem. While the causes of some
types of damage are relatively easy to diagnose, the causes of others can
be baffling. An engineer can also make sure that the repairs themselves
will not create more damage to the house and potentially result in
further problems.
Why can't I
patch the cracks in the wall?
Patching wall, ceiling, or floor cracks caused by marine clay
is only a cosmetic repair and is not a solution to the problem. Patching
does not address the source of the problem. Damage may reappear,
resulting in more extensive and costly repairs. If you patch up cracks
and later sell your house without disclosing the damage, you may be sued
by the purchaser.
Will every
house built in marine clays have problems?
Not every house that has been built in marine clay is or will
be experiencing problems. The house may be properly constructed to
withstand the soil conditions or may be in an area of more stable soils.
While no design can provide a 100 percent guarantee that problems will
not occur, certain safeguards can be taken to reduce the potential for
damage by marine clay. Engineering designs that have been properly
incorporated into new house construction or in repairs to existing houses
minimize the potential for later damage by marine clay. Homeowner
maintenance directed toward preventing moisture changes that could
trigger marine clay damage can also minimize future problems.
What can I do to prevent marine clay damage from
occurring?
As a homeowner, you can take certain steps to reduce the
potential for future marine clay damage. These steps lessen changes in
moisture that can lead to the shrinking and swelling of clays that cause
foundation and wall damage. Maintain a positive grade, or slope, away
from the house. This encourages surface water to run off away from the
house rather than to soak into the ground next to the house. Similarly,
make sure that gutters are in good repair and divert all downspouts away
from the house. Do not leave outside water faucets or hoses running
unattended, which can add large quantities of water to the soil next to
the house.
Keep all deeply-rooted trees and shrubs away from the house. Roots
growing around and underneath the foundation can take up large amounts of
soil moisture during the growing season, dry out the clays, and lead to
soil shrinkage and loss of foundation support.
What kind of county
assistance is available?
Fairfax County can help the
homeowner determine the source, extent, and potential solutions to
damages that may be caused by marine clay. Contact the Northern Virginia
Soil and Water Conservation District for technical help. Consumer
information helpful in selecting an engineering firm or a contractor to
repair damages can be obtained by contacting the Department of Consumer
Affairs. Contact the Department of Public Works and Environmental
Services for information of building permits. In certain cases, low
interest or deferred loans may be available for repair work. For
availability and criteria, contact the Department of Housing and
Community Development.