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House Foundations & Footings

Footing & House Foundation Systems

Foundations are one of the most important aspects of construction. This is the part of the structure which interacts with the earth. At first blush, this "interaction" may not appear to be significant. However, one must realize that the surface of the earth is covered by many different materials (soils). These materials (soils) have vastly different properties and react quite differently when loads are placed upon them. The problem is further complicated when we disturb these soils and move them from one location to another. This practice is generally referred to as "cutting and filling." Read this article for more information on cutting and filling.

Footing and foundation systems, when properly designed and constructed, allow us to construct buildings which will withstand the powerful forces of nature. Some of these forces are quite impressive. Gravity, soil swelling, frost heaving, hydrostatic pressure, etc. are just a few of the subtle hidden forces that can affect your house or building. These forces are powerful and should not be underestimated. For example, I have witnessed firsthand the ability of a 2' x 2' area of soil to raise 1,200 lbs of steel and concrete 1/2". This occurred after the soil underneath a column footing had been saturated with water after a moderate rainfall. I was quite impressed. You must respect these forces.

Let's start with the basics. Footings are the structural members which transmit the concentrated loads of the structure to the soil. These members come in various shapes and sizes and are generally constructed of steel-reinforced concrete. The footings are generally a minimum of two to three times wider than the width of the foundation wall. The thickness of the footer is a function of the weight of the structure above and the strength of the soil below the footer. A thicker footer (10 -12") will be stronger than a thinner (6 - 8") footer. The footer is usually installed immediately after excavation. The foundation is then constructed on top of the footer. Generally speaking, the footer is constructed independently of the foundation.

Foundations are also structural members. They basically are nothing more than giant beams. They carry loads, similar to structural steel I-beams. Foundations can be constructed from a variety of materials. They can be made from concrete, stone, concrete block, wood, steel, etc. Since they are difficult to replace, it is a wise idea to construct foundations using strong, durable, water resistant materials. The design criteria concerning foundations is very technical. You should consider consulting a structural engineer prior to building a foundation. This person will properly size the foundation and specify the materials from which it should be constructed.

Additional Reading

The following books offer a wealth of information concerning footings and foundations. In the event you cannot locate these books, your local library will probably have many similar books on the same topic. Good Luck!

  • Residential Foundations
    Jim Carr
    Home Builder Press, 2000

  • Simplified Design of Building Foundations, 2nd ed.
    James Ambrose
    John Wiley & Sons, Inc. 1988
  • Foundations and Concrete Work
    Fine Homebuilding Magazine
    Taunton Press, 2002

Column B10


6 Responses to House Foundations & Footings

  1. recently I worked on my house in south lake tahoe
    the house built in 1996 and on a slightl few degress slope , the house has basement and the basement flooded few years ago and I hired a builder to help in this issue and he did some work but still flooded three years ago, so this time I took some workers with me and I digged the foundtion till I reached the footings
    at one ara there was a small space to dig between the basment retainer wall like and
    another pole which was surrounded with dirt
    and I dd not come close to it becasue I thougt that by clearing the dirt around it I might weaken it,
    so I finished the job by putting french drains
    just about two inches deeper than the upper
    surfaces of the footings
    then I connected the drain to a sump pump
    and I insulated the wall with a waterproofing material
    my question
    how deep is those columns usually
    and did I did the right apporach

    thank you


  2. Hi,
    I am working with a builder constructing a new 2400 sf home in North Carolina. Purchased the lot, had a soil test and evaluation. Everything looked good. Construction started. Day 1 foundation staked, day 2 foundation was dug, day 3,4 footing was poured. 10 days later I got a message from the builder. They encountered adverse soil conditions and the additional cost would be $3,000 for washed stone, additional labor $1600, engineering 350. Do you think I am getting ripped off? could this be bogus? John

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