Over the long term, ground settling (or subsidence) may be a problem, as a slab foundation cannot be readily jacked up to compensate proper soil compaction prior to pour can minimize this. Remodeling or extending such a structure may also be more difficult. That being said, Frost Protected Shallow Foundations (or FPSF) which are used in areas of potential Frost Heave, are a form of Slab on Grade Foundations. This type of construction is most often seen in warmer climates, where ground freezing and thawing is less of a concern and where there is no need for heat ducting underneath the floor. The concrete is then placed into the mold, leaving no space between the ground and the structure. Slab-on-grade or floating slab foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. The general purpose of a strap footing is alike to those of a combined footing, where the spacing is possibly limited and/or the columns are adjacent to the property lines.ĭiagrams of the types of shallow foundations. Conversely, when the load among the columns is unequal, the combined footing should be trapezoidal.Ī strap footing is when individual columns are connected to one another with the use of a strap beam. When the load among the columns is equal, the combined footing may be rectangular. Also, when property lines make isolated footings eccentrically loaded, combined footings are preferred. Utilized when the spacing of the columns is too restricted, that if isolated footing were used, they would overlap one another. When more than one column shares the same footing, these are called combined footing. This type of footing is used when the structural load is relatively low, columns are widely spaced, and the soil's bearing capacity is adequate at a shallow depth. Sometimes, an isolated footing can be sloped or stepped at the base to spread greater loads.
Generally, each of its columns gets its footing to transmit and distribute the load of the structure towards the soil underneath. Isolated footing Īlso called single-column footing, it is a square, rectangular, or circular slab that supports the structural members individually. Detail Section of a strip footing and its wall.