Slab, Crawlspace or Basement?
Even though the foundation is one of the most important components of your home, there is often little choice in the matter. The type of foundation you use is most often determined for you. The type of lot you are building on, your location and your local building codes will dictate the type of foundation you can build. Natural conditions in the location you are building such as frost line, the type of soil, the depth of the water tables, as well as the overall water drainage, and the slope of your lot must all be considered when making the choice of which foundation to build. Local building codes examine all of these factors to make their recommendation as to what foundations are allowed in the area you want to build. The following are the three main types of foundations available: slab, crawlspace and basement.
Slab foundations are made up of a concrete slab that is typically 6 to 8 inches thick. The house then sits on the slab. Gravel is laid out first to facilitate drainage from underneath. Often times piping and utility hookups are set up to run through the slab. Rebar is used in some cases for added support, and expansion joists, or grooves along the surface inserted to handle any sort of cracking that might occur during the curing process, are added to all slabs as they are finished. Slabs are used most often in areas where there is high clay content in the soil. This can cause problems with settling due to inadequate subsurface drainage.
Slabs typically are the cheapest and fastest foundations to build. There is little excavation needed to set the slab, and it is poured simultaneously with the footings. The preparation for pouring the slab should be a day or less including the dry time for the concrete. Slabs are also less expensive then the other foundations because the floor of the home will sit directly on the slab, this eliminates the need for a floor support system to be constructed.
A crawlspace foundation is where the home is supported off of the ground level by approximately 2 feet. Stem walls extend from the footings around the perimeter of the foundation to support the home. Often times an alternative is used instead of the stem wall. This is called pier and beam. This is a system piers, which are a formation of rebar that are placed in holes and filled with concrete, that are tied into beams that will form a similar stem wall to support the home above. Crawlspaces are typically used in areas with high moisture, where excessive water can build up. Supporting the home off of the ground keeps it away from moisture that could cause damage. A crawlspace will also allow easy access to piping and utility areas underneath the home for both hookups and any necessary repairs.
Crawlspaces can be a fairly inexpensive foundation to build. There is often little excavation needed due to the home is supported off of the ground, and very little concrete is needed since it is only required in the footings and stem wall.
A basement is a popular foundation due to the added functionality it brings to a home. The basement can be used as storage space, finished off for living areas, or both. This living space is often finished off as recreation rooms, added bedrooms and bathrooms, and depending on the slope of your lot, nice windows and doors can be placed to make a walkout or daylight basement. The basement foundation combines elements of a slab and crawlspace. The floor in a basement is basically a slab, and the floor support system is what a crawlspace uses. The days the walls of the basement are most offered poured, but the decision between poured or block walls is often determined by local building codes. You can find basements all over the country, but areas with high water tables or unsettled soil will probably restrict you from building a basement due to potential flooding or cracking in the foundation walls.
Basements are the most expensive of the three foundations to build. More labor is required to excavate the site, poring the walls or setting the concrete blocks, and a basement is going to use more materials. A basement is also going to take more time to build. This is due to the added amount of work and the extra time needed to let all of the concrete set. An average basement will take 2-3 days to pour the concrete and up to a week to set.
As you search through our home plan collection you will notice plans will say what foundations they are available with. Some are available with all three types where others are only drawn with one. If you are unsure what foundation you will need, you can check with your county or local builders to see if there are restrictions as to what foundation you may build. If you find your dream home, but it is not available with the foundation you need, the plan can still work for you. Often times your builder can adjust the foundation to meet your needs or meet your local building code requirements. It is a good idea to discuss that with them first to make sure there wouldn't be any problems. If a new foundation sheet needs to be drawn, we have a staff designer who can look into making adjustments, or you can always have a local architect or designer make the adjustment for you.