1.1 General
A foundation transfers the load of a structure to the earth and resists loads
imposed by the earth. A foundation in residential construction may consist of a footing,
wall, slab, pier, pile, or a combination of these elements. This course will addresses the
following foundation types:
• crawl space;
• basement;
• slab-on-grade with stem wall;
• monolithic slab;
• piles;
• piers; and
• alternative methods.
The most common residential foundation materials are concrete masonry (i.e., concrete
block) and cast-in-place concrete. Preservative-treated wood, precast concrete, and other
methods may also be used. The concrete slab on grade is the most popular foundation
type in the Southeast; basements are the most common type in the East and Midwest.
Crawl spaces are common in the Northwest and Southeast. Pile foundations are
commonly used in coastal flood zones to elevate structures above flood levels, in weak or
expansive soils to reach a stable stratum, and on steeply sloped sites. Figure 1.1 depicts
different foundation types; a brief description follows. A crawl space is a building
foundation that uses a perimeter foundation wall to create an under-floor space that is not
habitable; the interior crawl space elevation may or may not be below the exterior finish
grade. A basement is typically defined as a portion of a building that is partly or
completely below the exterior grade and that may be used as habitable or storage space.
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A slab on grade with an independent stem wall is a concrete floor supported by the soil
independently of the rest of the building. The stem wall supports the building loads and in
turn is supported directly by the soil or a footing. A monolithic or thickened-edge slab is
a ground-supported slab on grade with an integral footing (i.e., thickened edge); it is
normally used in warmer regions with little or no frost depth but is also used in colder
climates when adequate frost protection is provided. When necessary, piles are used to
transmit the load to a deeper soil stratum with a higher bearing capacity, to prevent
failure due to undercutting of the foundation by scour from flood water flow at high
velocities, and to elevate the building above required flood elevations. Piles are also used
to isolate the structure from expansive soil movements. Post-and-pier foundations can
provide an economical alternative to crawl space perimeter wall construction. It is
common practice to use a brick curtain wall between piers for appearance and bracing
purposes. The design procedures and information covered in this course are
• foundation materials and properties;
• soil bearing capacity and footing size;
• concrete or gravel footings;
• concrete and masonry foundation walls;
• preservative-treated wood walls;
• insulating concrete foundations;
• concrete slabs on grade;
• pile foundations; and
• frost protection.
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