Slab-on-grade foundations are shallow
foundations that are most often constructed of
reinforced concrete. Slab-on-grade foundations
can be built quickly and are relatively
inexpensive to build. The function of a
slab-on-grade foundation is not to resist or
limit the amount of heave that might occur
beneath a slab foundation, but to move up and
down with the shrink and heave. Slab-on-grade
houses do not have basements.
Shallow foundations are susceptible to seasonal
movement from rainfall, drought, freeze/thaw
cycles, and temperature changes and
transpiration of moisture thru the roots of
large plants and trees.
| Pier
and beam foundations |
|
Pier and beam foundations, as the name suggests,
is a concrete footing and pier which supports
wood beams and floor joists. These foundations
usually have crawl spaces underneath the home.
Basements are most often constructed in northern
climates where freeze thaw conditions occur and
the footing depth must extend beneath the frost
line- often four or more feet below the surface.
In many of these cases, builders will go ahead
and excavate for a basement and build basement
walls that provide the support for the house.
The bottom of the basement is typically below
the depth over which the majority of the soil’s
shrink or swell due to climate occurs. Basements
can suffer basement floor heave and lateral wall
movement, however.
Deep foundations reach depths that are not
normally affected by seasonal environmental
changes and are considered to be out of the zone
of influence.
There are a multitude of other types of both
shallow and deep foundations
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