At that time, concrete generally attains about 85% of its fully cured compressive strength.Ĭoncrete is a mixture of cement, water, sand, gravel, crushed rock, or other aggregates. Given that concrete strength increases at a diminishing rate with time, the specified compressive strength is usually associated with the strength attained after 28 days of curing time. The concrete compressive strength may be verified in accordance with ASTM C39 (ASTM, 1996). For example, 3,500 psi concrete may be used for improved weathering resistance in particularly severe climates or unusual applications. The concrete compressive strength used in residential construction is typically either 2,500 or 3,000 psi, although other values may be specified. ![]() A brief discussion of the properties of concrete and masonry follows. In addition, soils are considered a foundation material. In addition, the designer is referred to the applicable design standards for symbol definitions and additional guidance, since the intent of this article is to provide supplemental instruction in the efficient design of residential foundations.Ī residential designer using concrete and masonry materials must have a basic understanding of such materials, as well as an appreciation of variations in the materials’ composition and structural properties. Wood design procedures are used to design the connections between the foundation system and the structure above and follow the allowable stress design method for wood construction. Masonry design procedures follow the allowable stress design method of ACI-530 (ACI, 1999). For this reason, some supplemental design guidance is provided when practical and technically justified. soil-bearing capacity and footing size Ĭoncrete design procedures generally follow the strength design method contained in ACI (American Concrete Institute)-318 (ACI, 1999), although certain aspects of the procedures may be considered conservative relative to conventional residential foundation applications.The design procedures and information in this section covers: ![]() It is common practice to use a brick curtain wall between piers for appearance and bracing purposes. Post-and-pier foundations can provide an economical alternative to crawlspace perimeter wall construction. Piles are also used to isolate the structure from expansive soil movements. 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 floodwater flow at high velocities, and to elevate the building above required flood elevations. 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. The stem wall supports the building loads and, in turn, is supported directly by the soil or a footing. 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.Ī slab on grade with an independent stem wall is a concrete floor supported by the soil independently of the rest of the building. 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.Ī crawlspace is a building foundation that uses a perimeter foundation wall to create an under-floor space that is not habitable the interior crawlspace elevation may or may not be below the exterior finish grade. Crawlspaces are common in the Northwest and Southeast. 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. Preservative-treated wood, precast concrete, and other methods may also be used. ![]() The most common residential foundation materials are concrete masonry (i.e., concrete block) and cast-in-place concrete. In this inspection training article, we'll discuss the following foundation types: ![]() A foundation in residential construction may consist of a footing, wall, slab, pier, pile, or a combination of these elements. A foundation transfers the load of a structure to the earth and resists loads imposed by the earth.
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