Building Foundations

Foundations The foundation of a building transfers the weight of the building to the ground. Normally, every building has a number of individual foundations, commonly called “footings”. Usually each column of the building will have its own footing. https://en.wikipedia.org/wiki/Wall_footing https://en.wikipedia.org/wiki/Strap_footing

Soil Bearing Capacity Since the weight of the building rests on the soil, engineers must study the properties of the soil very carefully to ensure it can carry the load (weight) of the building To properly support a building, the soil must be firm and strong. It is common for the soil near the surface of the earth to be loose and weak. If a building is rested on this soil, it will sink. https://en.wikipedia.org/wiki/Soil_mechanics

Types of Foundations 2 Categories: Shallow and Deep Shallow Can be made in depths of as little as 3 feet Used for small, light buildings Deep Can be made at depths of 60 - 200 feet Used for large, heavy buildings https://en.wikipedia.org/wiki/Shallow_foundation http://cdn.wonderfulengineering.com/wp-content/uploads/2014/07/What-is-a-pile8.jpg

Shallow Foundations: Individual Footings Individual footings are one of the most simple and common types of foundations. Used when the load of the building is carried by columns Each column will have its own square of rectangular pad of concrete on which it will sit. http://www.123rf.com/stock-photo/concrete_footing.html

Shallow Foundations: Strip Footing Commonly found in load-bearing masonry construction, and act as a long strip that supports the weight of an entire wall. Used when loads are carried by an entire wall, instead of isolated columns. www.builderbill-diy-help.com

Shallow Foundations: Raft or Mat Foundation Used most often when basements are to be constructed. The weight of the building is spread evenly over the entire footprint of the building. Used where the soil is weak, and where loads have to be spread out over a large area https://en.wikipedia.org/wiki/Shallow_foundation

Deep Foundations: Pile Foundations A pile is a long cylinder of a strong material that is pushed deep into the ground so the structures can be supported on top of it Used when there is a layer of weak soil at the surface, or when a building has very heavy concentrated loads, such as a high rise 2 Types: End-bearing, and Friction End-bearing piles: the bottom end of the pile rests on a layer of strong soil or rock Friction piles: the pile transfers the load across the full height of the pile, by friction, and works to transfer the forces to the soil

What are piles made of? Piles can be made of wood, concrete, or steel. www.14thstviaductreplacement.com https://en.wikipedia.org/wiki/Pier www.foundationpiledriving.com

How are piles used? As pile foundations carry a lot of load, they must be placed to ensure the soil is not overloaded beyond its bearing capacity.

How are piles put into place? Piles are first cast at ground level, then hammered or driven into the ground using a “pile driver”. The pile driver lifts and holds the pile perfectly vertical, then hammers it into the ground blow by blow until it cannot be driven any further into the soil. http://www.understandconstruction.com/pile-foundations.html

Helical Pile Helical piles are steel tubes that have helical (spiral) blades attached to them. They can be drilled into the ground from above Once the pile is driven into the ground, a pile cap is poured on top to prepare it for construction above. www.magnumpiering.com www.haywardbaker.com

Sources Understand Construction http://www.understandconstruction.com/introduction-to-foundations.html