These foundation types are easier to maintain in areas with expansive soils, like Houston, TX.
CRAWL SPACE FOUNDATIONS
Foundations with a crawl space are called pier and beam, or block and base, and use sills and floor joist made from wood. Pier and beam types of foundations are one of the most common types of spread foundations people are familiar with. Spread foundations distribute the weight of the building over a large area. Foundation problems occur for several reasons: too much or too little water or changing of existing loads.
Buildings with a crawl space sitting off the ground; allow workers to enter the space below the house and allows for improved ventilation. This space, besides making it easier for other types of repair, allows people to repair foundation problems by replacing damaged beams, sills and adding additional pads and blocks.
Block and base foundations are a shallow foundation usually less than one foot in the ground. Block and base describes how this system is built, pre-fab blocks, usually 8x8x16, are set on a base pad. The base pad is usually bigger than the block. Each base and block setting is called a post, and these posts are usually placed 5 to 10 feet apart, depending on engineering and loads.