House Foundation Types, Uses, and Pros and Cons

Full or Daylight Basement Foundation

A basement foundation is the deepest of the 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 average cost of a basement foundation is $34,250. This makes a basement foundation the most expensive: about four times more expensive than a concrete slab foundation.

The chief advantage of a basement is the extra space it provides for storage or living. In some homes, finishing a basement can nearly double the amount of living space. 

Also, a basement can be conditioned (meaning that it is heated or cooled) like the rest of the house. A conditioned basement provides a buffer for upper floors, making them easier to heat or cool.

Full Basements

A full basement matches the perimeter of the house above. So, if the house's ground floor is 800 square feet, the entire 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. 

The average cost to remodel a basement is $25,000. Remodeling a basement means, at a minimum, installing a dry subfloor, moisture-tolerant flooring, insulated walls, and a ceiling.

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.

Daylight Basements

One variation of the entire basement is the daylight basement, sometimes called a partial basement. Built against a slope, the daylight basement has one or more sides wholly 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. Due to the increased natural light and air, daylight basements avoid many of the unpleasant aspects of basement living. Mold and mildew are easier to manage in daylight basements than in full basements.

Crawlspace Foundation

Foundations create a crawlspace consisting of short foundation walls on footings. The walls may be very short—creating a space you have to crawl through—or they can be 4 feet tall, providing room for storage and sometimes a furnace or other equipment. 

Crawlspace floors are usually built at grade or above grade. The crawlspace's lower part (not the house's upper floor) is at ground level or higher. Sometimes, crawlspaces are built below grade, much like a basement. Precautions must be taken to allow flooded water to escape. Owners of ground-level homes or with below-grade crawlspaces may need to pay higher flood insurance premiums.

The average cost of a crawlspace foundation is $14,500, twice that of a concrete slab foundation and more than half that of a basement foundation.

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. Moisture control and water leaks and seepage are other considerations with crawlspace foundations.

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 are typically made with poured or mortared concrete blocks. 

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.

A slab-on-grade is less expensive than a subgrade (full basement or crawlspace) foundation and can offer better protection against termite infestation (common in warmer climates).

Expect to pay an average of about $8,250 for a concrete slab foundation. Compared to the average cost of $14,500 for a crawlspace foundation, a concrete foundation is almost half the cost of a crawlspace foundation.

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 to access the pipes. With a slab foundation, you won't have storage space or additional living space for your home. It is also not feasible to retroactively add a basement or crawlspace.

Insulated Concrete Form (ICF)

Insulating concrete forms, usually made from high-density foam, are used when pouring concrete walls, forming the wall structure. They stay in place after the concrete has hardened, strengthening and insulating the system from outside temperature and sound. They are modular, making their construction faster. They are also recommended for their durability in hurricanes, earthquakes, and other natural disaster zones.

A significant benefit of using ICF construction is that you can use 60% smaller heating and cooling units to service the same floor area. Since it's more energy efficient, it may qualify for tax credits in some areas. Property insurers may also reduce your rate since ICF properties are less prone to damage from earthquakes, floods, hurricanes, fires, and other natural disasters. Also, these structures do not contain wood, so maintenance and upkeep costs are less since they don't rot or can't be damaged by insects or rodents.

A downside to using ICF is that it is not structurally sound if it does not cure correctly. Also, since it is not porous like concrete, humidity may be higher indoors than some foundations that breathe. Unlike other systems, making modifications, like adding windows or doors, is also tricky, requiring demolishing that portion of the structure.

Traditional concrete foundations will be the cheapest option at $5 to $25 per square foot. Still, in the long run, ICF will be the most cost-effective considering all its upsides with energy efficiency, tax credits, and insurance rates. ICF foundation and walls cost $10 to $30 per square foot, according to HomeAdvisor.

ICF construction costs about 40% less than conventional (basement) construction. It is more expensive to use ICF above grade but not when adding large openings. ICF construction only needs reinforcing steel around its opening, while conventional construction methods require large headers and supporting posts with large openings.