Crawl space foundation is another popular foundation option after concrete slab-on-grade foundation and monolithic slabs. The crawlspace foundation is similar to a slab foundation where concrete footing provides the basis for the foundation.
Construction of Crawl Space Foundation
- Footings: Home builders need to excavate and pour footings just as it is done with a standard slab on grade. These footings carry weight of the entire house. Therefore, footings need to be strong enough. Depth, width and reinforcement of footings depend on size of the house and condition of the soil where construction of the house takes place.
- Stem Walls: Stem walls can be poured in place of reinforced block. Reinforced block is typically used when the foundation is hillside. Hillside foundations sometimes require a stepped foundation. Blocks helps easier stepping of the foundation stem walls.
- Termite Treatment: Whether it is a crawl space, slab or basement, make sure you have termite treatment for your foundation. You should go for a termite treatment process even if it is not a requirement in your municipality. This is important to get good resale value. You can claim that it has been termite treated.
- Piers: Concrete or block piers are set inside the crawl space area. Piers support beams or girders, which, in turn, support the floor joists. Size of pier footings may vary depending on the load. A blueprint specification should indicate what the necessary footing size should be.
- Beams and Girders: A wide span crawl space foundations will require beams or girders to support the floor joists. A home built with a small foot print may not use piers and beams because floor joists can span from stem wall to stem wall.
- Floor Joists: Floor joists are set on the crawl space foundation stem wall. Once the stem wall is complete, the framing contractor will begin the flooring system starting with building a short pony wall to raise the flooring if the stem walls are stepped. It is then necessary to frame up the wall to a level elevation to set floor joists.
- Plumbing and HVAC: Once the framing is complete, the plumbing and HVAC contractors will start their work in the crawl space foundation and run pipes and ductwork underneath the floor. It is recommended to insulate individual water lines. Keep in mind that crawl space is the exterior of the house and is subject to winter freezing unless sealed.
Crawl Space Insulation
You can insulate the stem walls of the crawl space foundation by using insulated concrete forms (ICF’s) and by blowing in or using fiberglass batts in the pony wall. Because the crawl space is vented, there will be free movement of air. Still, insulation can regulate crawl space temperature.
Insulating crawl space: As stated above, crawl space is exterior of the house unless completely sealed; all floor joists should be insulated. You can discuss with your insulation contractor about options available for your house. The most common and the simplest form of insulation used in flooring joists is fiberglass batt insulation. Using fiberglass for insulation has following advantages:
- It is difficult to blow in insulation in the flooring area.
- Many water lines run through the floor joists. Therefore, it using other insulating materials such as loose cellulose would be difficult and also maintenance would get difficult. Maintain a high standard when installing batts in the crawl space.
Crawl Space Venting and Access
Any standard crawl space foundation should have venting. Plumbing, gas and HVAC run in the crawl space. Venting helps prevent moisture which can lead to mold growth and deterioration of wood. Work on calculations for how many square feet of venting is required per cubic foot of vented area. Framers can work on this to know the number of vents needed.
Access to the crawl space is necessary to allow maintenance in future. Keep this in mind when planning the crawl space foundation.
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