Strip foundations are made out of a continuous strip of material, commonly concrete, that is constructed centrally underneath load-bearing walls. The foundation slab forms the base upon which house structures are built. It provides support for these buildings and prevents their collapse. The foundation should be strong enough to carry its intended load without failure. The size of the foundation depends on how much weight it will have to bear and the type of loading it will experience. The two main types of foundations are footings and caps. Footings are trenches or holes dug below the frost line with the intention of preventing water from reaching the interior of the home. The depth of the footing depends on how wet or dry your soil is. If you can't dig down deep enough, then you'll need to use gravel or other materials to create a drainage system. Caps are the surface structures placed on top of footings to keep out moisture and provide some levelness to the ground surface. They can be as simple as a stone or brick wall, but they may also be a series of blocks or piers supporting a roof over the footings. Caps and footings help prevent erosion and maintain the integrity of the land surface around the foundation. Erosion is the wearing away of soil by water, wind, ice, and gravity.