The first thing that needs to be done on any construction site is site preparation. The three most common types of house foundations are basement, crawl space or slab. These are discussed in another article.
The site-preparation crew (also commonly referred to as the excavator) usually uses heavy equipment such as a backhoe and/or bulldozer to clear the site of any trees, rocks and debris, level the site if necessary and dig a hole in the ground necessary for the foundation being built.
If the house is built on a slab, the excavators digout approximately 8 inches deep and then completely level an area for the pad. In western Washington, slab foundations are very unusual; in drier southern climates they are much more common. For a crawl space, the crew digs a hole that slightly reminiscent of a swimming pool. In this digout, forms are built into which liquid concrete will be poured and set to become the footings and walls of the foundation. At points where a beam will sit, thickened areas of concrete form pads to support the additional weight for the beams and whatever the beams are supporting. These foundation footings and walls forms the beams which the walls of the house will rest on. When a house is built on a basement foundation, the digout is 7-8 feet deep.
Around the perimeter of the digout, the excavator will also dig about 2-3 feet wider on each side than the actual footprint of the house. This is so that workers can work around the perimeter as the concrete is being poured.
Concrete takes some time to ‘cure’ or harden to gain full strength to support the weight of the house. During this curing, the excavators will come back and ‘backfill’ or fill in dirt where in the trenches that had been dug for temporary use. Then the framing of the house can begin.