Foundations
The word foundation is used to mean
- Construction below grade, such as footings, cellar,
or basement;
- The composition of the earth on which the
building rests; and
- Special construction, such as pilings and piers used
to support the building.
The foundation bed may be composed of solid rock,
sand, gravel, or unconsolidated sand or clay. Rock, sand,
or gravel are the most reliable foundation materials.
These are the three most common foundations for
homes. Unconsolidated sand and clay, though found in
many sections of the country, are not as desirable for
foundations because they are subject to sliding and
settling. Capillary breaks have been identified as a key
way of reducing moisture incursion in new construction.
The footing distributes the weight of the building over a
sufficient area of ground to ensure that the foundation
walls will stand properly. Footings are usually concrete;
however, in the past, wood and stone have been used.
Some older houses were constructed without footings.
Although it is usually difficult to determine the condition
of a footing without excavating the foundation, a footing
in a state of disrepair or lack of a footing will usually be
indicated either by large cracks or by settlement in the
foundation walls. This type of crack is called a Z crack.
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Foundation wall cracks are usually diagonal, starting from
the top, the bottom, or the end of the wall. Cracks that do not extend to at least one edge of the wall
may not be caused by foundation problems. Such wall
cracks may be due to other structural problems and
should also be reported.
The foundation walls support the weight of the structure
and transfer this weight to the footings. The foundation
walls may be made of stone, brick, concrete, or concrete
blocks. The exterior should be moisture proofed with
either a membrane of waterproof material or a coating of
portland cement mortar. The membrane may consist of
plastic sheeting or a sandwich of standard roofing felt
joined and covered with tar or asphalt. The purpose of
waterproofing the foundation and walls is to prevent
water from penetrating the wall material and leaving the
basement or cellar walls damp.
Holes in the foundation
walls are common in many
old houses. These holes
may be caused by missing
bricks or blocks. Holes and
cracks in a foundation wall
are undesirable because
they make a convenient
entry for rats and other
rodents and also indicate
the possibility of further
structural deterioration.
Basement problems are a
major complaint of
homeowners.
Concrete is naturally
porous (12%"18% air).
When it cures, surplus
water creates a network of
interconnected capillaries.
These pores let in liquid
water, water vapor, and
radon gas. Like a sponge,
concrete draws water from
several feet away. As concrete ages, the pores get bigger as
a result of freezing, thawing, and erosion.
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Concrete paints, waterproofing sealers, or cement coatings
are a temporary fix. They crack or peel and cannot stop
gases such as water vapor and radon.
Damp basement air spreads mold and radon through the
house. Efflorescence (white powder stains) and musty
odors are telltale signs of moisture problems.
Basement remodeling traps invisible water vapor, causing
mold and mildew. Most basements start leaking within
10 to 15 years. The basement walls and floors should be
sealed and preserved before they deteriorate. The basement
floor should be concrete placed on at least 6 inches of
gravel. The gravel distributes groundwater movement
under the concrete floor, reducing the possibility of the
water penetrating the floor. A waterproof membrane, such as
plastic sheeting, should be laid before the concrete is
placed for additional protection against flooding and the
infiltration of radon and other gases.
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Footings 
