Spread Footing Foundation
A spread footing foundation, which is typical in residential building, has a wider bottom portion than the load-bearing foundation walls it supports. This wider part "spreads" the weight of the structure over more area for greater stability.
The design and layout of spread footings is controlled by several factors, foremost of which is the weight (load) of the structure it will support as well as penetration of soft near-surface layers, and penetration through near-surface layers likely to change volume due to frost heave or shrink-swell.
These foundations are common in residential construction that includes a basement, and in many commercial structures. But for high rise building it is not sufficient.
A spread footing which changes elevation in several places in a series of vertical "steps" in order to follow the contours of a sloping site or accommodate changes in soil strata, is termed a stepped footing.
Read more about this topic: Shallow Foundation
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