Concrete Foundations – Footings

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    Concrete is the fastest and easiest way to form a buildings foundation. Aluminum or wood forms are used to define the shape and placement of the wall and then concrete is poured into the form and allowed to cure.

    Foundations have 3 basic parts: the footing, the wall and the Slab or floor. 

    Footing specifications must be designed by an engineer or qualified architect. Although special considerations for your project may be necessary most of the time the specifications will be standard for your type of building located in your general area. For instance a single family home under three stories tall with good soil conditions will usually have a 12×24” perimeter footing located minimum 1 foot below frost line or at the base of the basement wall.

    To prepare the site a surveyor will use a map of your lot and a transit to set reference stakes. The stakes will be located outside of the area to be excavated and the foundation crew will use their own laser levels and tape measures to locate where forms should be set.

    Excavation will extend past the boundary of the footing by about 2 feet. This will allow enough room for crews to work. The depth of the excavation must extend far enough down to pass the frost line and all organic materials like topsoil must be removed. Over the life of your home topsoil will break down and cause voids or sink holes. Frost will also cause heaving and damage.

    To make sure your footing is on good soil a compaction test may need to be performed. Often when homes are being built close enough together in large developments Inspectors will assume that compaction rates are similar and only require one test for the area.

    The footing will run around the perimeter of the building and can be dug by hand or formed with 2’x12″ boards but most likely it will be dug by a backhoe. An architect will set the size of the footing needed to support the home but often when the backhoes bucket is slightly larger then the footing size you will see the hole being dug one bucket wide.

    Before concrete is poured Black ABS Drain Tile pipe will be run around the outside of the foundation and the end will go under the footing and into the basement where your sump pump will be placed.

    Rebar Rod will also be positioned in the center of the footing by placing it on supports.

    Once the prep work has been finished concrete will be poured into the footing. Since Concrete is a liquid it will (pretty much) self level in the hole.

    Rebar rod will now be inserted into the footing and extend up into the area where the wall will be set. This will tie the wall into the footing.

    After about 24 hours the Foundation Walls can be formed and poured.

    In this HowTo we covered the basic footing for a single family home. Your location may require different methods. In sandy beach front areas you can not dig deep enough to hit Ledge or compactable soil so you must make use of Caissons or Piers that are driven into the sand. In other areas you may not need to account for frost so a perimeter footing may only be just below grade and your home may not have a basement or kneewall. However in all buildings you must have a stable footing to support the structure.

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