Basement foundations are, basically, an accessible space between the soil and the 1st floor framing of a house. They have walls that are at least eight feet high and are usually thicker than standard foundation walls. Basements are predominant in cold climates where footings are forcibly deep due to frost lines and are usually full-height to allow extra living or storage space. In some areas basement foundations are not possible because of high water tables or the obstruction created by solid rock near to the surface.
Full-height basement foundations consist of a slab on grade with full height footing walls. First the site will be excavated to the necessary depth. The hole does not necessarily need to be 8' deep or more. The top of footing walls will need to be above finish grade at least one to two feet to keep water away from the structure. After excavation a layer of crushed gravel should be put down and compacted. This gravel will provide drainage under and around the slab and footings. Next, the footing walls will be built. These may consist of poured concrete or block masonry reinforced with carbon steel bars or rods. Traditionally brick was also used for foundation walls but is much less common today because steel reinforced concrete or cement blocks are much more structurally sound. The depth below finish grade or the amount of fill dirt that will press against the footing wall will determine the thickness of the wall. Be sure that you or your contractor consult a structural engineer before pouring footings. It is essential to have a quality, durable foundation beneath your home.
The basement floor will simply be a slab on grade, poured directly onto the compacted gravel, which will span the interior of the footings. This slab is several inches thick and reinforced with wire mesh or steel bars. It is also a good idea to have any portion of the basement walls that are below ground waterproofed. Waterproofing can be done on existing basements, but if you are building new, then it is an excellent idea to seal it either at the time of construction or before anything is moved into the new basement. Epoxy or latex waterproof mixes can be purchased at local home improvement stores and applied with relative ease.
If a home is built on a slope or hillside it may very well have a daylight, or walk-out, basement. Daylight basements have usually one side of the foundation exposed with doors and/or windows. Daylight basements can be very advantageous, especially if the basement is finished. One important note, if you have, or plan on building, a standard basement, know that if you wish to finish you will by law need an egress, or access, window which acts as a fire exit.
Full-height basement foundations do cost more than slab on grade or low-height, crawl space foundations but, if you have the opportunity, they are a worthwhile investment. Not just for added worth of your home should you sell, but also for that extra storage space or living space. Basements add an amazing amount of square footage to a home without eating up the entire lot.
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