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Structures or other constructed works are supported on the earth by foundations. The word “foundation” may mean the earth itself, something placed in or on the earth to provide support, or a combination of the earth and the elements placed on it. The foundation for a multistory office building could be a combination of concrete footings and the soil or rock on which the footings are supported. The foundation for an earth-fill dam would be the natural soil or rock on which the dam is placed. Concrete footings or piles and pile caps are often referred to as foundations without including the soil or rock on which or in which they are placed. The installed elements and the natural soil or rock of the earth form a foundation system; the soil and rock provide the ultimate support of the system. Foundations that are installed may be either soil-bearing or rock-bearing. The reactions of the soil or rock to the imposed loads generally determine how well the foundation system functions. In designing the installed portions, the designer must determine the safe pressure which can be used on the soil or rock and the amount of total settlement and differential settlement which the structure can withstand.

The installed parts of the foundation system may be footings, mat foundations, slab foundations, and caissons or piles, all of which are used to transfer load from a superstructure into the earth. These parts, which transmit load from the superstructure to the earth, are called the substructure (see illustration).

Examples of foundation systemsenlarge picture
Examples of foundation systems

Footings or spread foundations are used to spread the loads from columns or walls to the underlying soil or rock. Normally, footings are constructed of reinforced concrete; however, under some circumstances they may be constructed of plain concrete or masonry. When each footing supports only one column, it is square. Footings supporting two columns are called combined footings and may be either rectangular or trapezoidal. Cantilever footings are used to carry loads from two columns, with one column and one end of the footing placed against a building line or exterior wall. Footings supporting walls are continuous footings.

Mat or raft foundations are large, thick, and usually heavily reinforced concrete mats which transfer loads from a number of columns or columns and walls to the underlying soil or rock. Mats are also combined footings, but are much larger than a footing supporting two columns. They are continuous footings and are designed to transfer a relatively uniform pressure to the underlying soil or rock.

Slab foundations are used for light structures wherein the columns and walls are supported directly on the floor slab. The floor slab is thickened and more heavily reinforced at the places where the column and wall loads are imposed. See Caisson foundation, Retaining wall

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.
References in classic literature ?
Yet there were in the duke such boldness and ability, and he knew so well how men are to be won or lost, and so firm were the foundations which in so short a time he had laid, that if he had not had those armies on his back, or if he had been in good health, he would have overcome all difficulties.
The Indian right of possession itself stands, with regard to the greater part of the country, upon a questionable foundation. Their cultivated fields; their constructed habitations; a space of ample sufficiency for their subsistence, and whatever they had annexed to themselves by personal labor, was undoubtedly, by the laws of nature, theirs.
A sentimental reformer in architecture, he began at the cornice, not at the foundation. It was only how to put a core of truth within the ornaments, that every sugarplum, in fact, might have an almond or caraway seed in it -- though I hold that almonds are most wholesome without the sugar -- and not how the inhabitant, the indweller, might build truly within and without, and let the ornaments take care of themselves.
We have seen that we are driven to believe in the subsidence of those vast areas, interspersed with low islands, of which not one rises above the height to which the wind and waves can throw up matter, and yet are constructed by animals requiring a foundation, and that foundation to lie at no great depth.
How many times I wished them, and have often wished since, that by some power of magic I might remove the great bulk of these people into the county districts and plant them upon the soil, upon the solid and never deceptive foundation of Mother Nature, where all nations and races that have ever succeeded have gotten their start,--a start that at first may be slow and toilsome, but one that nevertheless is real.
'The foundation is in the wickedness and falsehood of the world,' said I, 'and in the fact that Mr.
Separate, stand-alone foundations established by Catholic dioceses to focus on fundraising and endowment growth are becoming increasingly more common, according to a new report.
Los Angeles, CA, July 09, 2017 --( A foundation repair and construction company, Julian Construction (, is informing homeowners on the five types of home foundations.
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The NH Charitable Foundation is among the 10 foundations nationally to receive the 2017 U.S.
For the second consecutive year, private and community foundations experienced lower investment returns in the 2015 fiscal year, the Council on Foundations and Commonfund Institute reported this week.

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