Every house is built on a foundation, but not every house is built on the same type of foundation. Home foundation type is based on factors such as house design, geographical location and climate, soil and moisture conditions, and the project budget.
Foundation types vary, but likely your house or addition does or will have one of these three foundations: full or daylight basement, crawlspace, or concrete slab-on-grade. These are serviceable—and sometimes even flexible—foundations that work for millions of homes across a variety of climates and needs.
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Full or Daylight Basement Foundation
A basement foundation is the deepest of the three major foundation types. A full basement matches most or all of the floor space of the level above and it is generally at least 7 feet high. Newer homes typically have taller basements to facilitate conversion into living space.
The primary advantage of a basement is all the extra space that it provides for storage or for living. In some homes, finishing a basement can nearly double the home's living space. A basement can be conditioned (meaning that it is heated or cooled) like the rest of the house or it can be unconditioned.
A full basement is one that matches the perimeter of the house above. So, if the ground floor of the house is 800 square feet, the full basement's square footage is also 800 square feet—more or less.
A full basement consists of structural foundation walls that bear on foundation footings running along the perimeter of the basement. Footings usually extend below the frost line, the depth to which the ground freezes in winter.
A full basement with a ceiling 7 feet high or higher is a valuable asset to a home. It can be converted into habitable living space or turned into a home gym, children's play area, home theater, or just left for storage.
One variation of the full basement is the daylight basement, sometimes called a partial basement. Built against a slope, the daylight basement has one or more sides that are completely embedded in the ground, from floor to ceiling. However, as the slope descends, one or more sides of the foundation are exposed and can have large windows and doors to bring in daylight.
Daylight basements are often more practical for conversion into living space than full basements. They offer the possibility of adding a separate entrance, a necessity if you plan to rent out the space. Daylight basements, too, avoid many aspects of basement living, due to the increased natural light and air. Mold and mildew are easier to manage in daylight basements than in full basements.Pros
Living space possibility
Increased storage room
Often water problems
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Foundations that create a crawlspace consist of short foundation walls that stand on footings. The walls may be very short—creating a space that you literally have to crawl through—or they can be in the range of 4 feet tall, providing room for storage and sometimes a furnace or other equipment.
Typically, crawlspaces are unheated spaces and may be ventilated with small vents that penetrate the foundation walls to promote a small amount of airflow through the crawlspace.
For foundations in areas with certain types of clay soils, caissons (or deep holes filled with concrete) are often drilled down to bedrock. The foundation is then placed on them in lieu of footings. This allows for the expansion and contraction associated with certain soils.
Crawlspace foundations are less expensive than full basements because they require less excavation and less foundation wall material and labor to build. Like full basement foundations, crawlspace walls typically are made with poured concrete or mortared concrete block.Pros
Access to below-floor services like pipes or wires
Difficult to crawl through
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Concrete Slab-On-Grade Foundation
A slab-on-grade foundation is a solid concrete slab that rests on the ground. Grade refers to ground-level, and slab refers to the monolithic concrete pad.
Slab-on-grade foundations are most commonly used in climates that do not experience ground freezing and thawing, as this can lead to cracks in the concrete and shifting of the foundation.
Slab-on-grade foundations tend to be less expensive than the subgrade (full basement or crawlspace) foundations and can offer better protection against termite infestation (also common in warmer climates).
One notable downside of slab foundations is that water supply and drainage pipes are encased in the concrete. In the event of a problem, the concrete slab must be cut into to access the pipes. Also, slab foundations offer no storage or living space below, nor is it feasible to retroactively add a basement or crawlspace.Pros
Impervious to insects
No storage or living space
Pipes encased in concrete