Carport Foundation Requirements
Although your carport can be installed without a finished floor, anchoring to a concrete foundation gives you a more secure structure and easier maintenance. Some local building authorities require a foundation – you can learn more about this on our page covering engineered plans and permits.
Concrete Foundation Planning: You should plan for a foundation that is 2” longer than your carport, but of the same width. That is, if you’ve purchased a kit for a carport 24’ wide and 28’ long, the foundation should measure 24’ wide by 28’ and 2” long. Before actually installing your foundation, you’ll need to prepare the building site. Instructions for this step are included in the instruction booklet shipped with your steel carport kit. For additional information on site preparation, click here.
Foundation Slab Depth: If you plan to park normal-sized passenger vehicles in your carport, the slab should be made 4” thick, using concrete rated at 2500 psi.
If you plan on using the carport to house large, heavy vehicles such as larger trucks or RVs, it’s best to use a 6” slab, to support the extra weight. In this case, 4000 psi concrete is recommended.
In either case, your slab’s concrete should be reinforced. This can be done at the mixing plant with the addition of fiber mesh to the concrete mix, or on your building site by placing #3 reinforcing bar (“rebar”) on a 24” pattern.
Expansion joints should be added during the floor’s finishing, either with a trowel or by saw cutting, at the appropriate point of the finishing process.
Footings for Your Carport Foundation
Perimeter footings should be included in the pouring of your carport floor slab. As shown in the drawings that follow, typical perimeter footings are 12 inches wide and 12 inches deep. (The depth measurement includes the thickness of the slab.)
Reinforcing bar is also normally required in footings. This is done with #4 rebar, running continuously at both the top and bottom of the footing.
Since prices vary from area to area, the best way to learn the cost for pouring your carport’s concrete slab and footings is to contact a local contractor.
Bare-Ground Carport Foundations
Your carport can be installed directly to the ground, if you prefer. This type of installation is best done using concrete caissons to securely anchor the structure.
Space your caissons along the length of your carport, at the same distance apart as its upright framing – either every five feet, or every four feet. Each caisson requires a hole, 10” or more across and at least 30” deep. The best method for making your caisson holes is with a post-hole digger or auger, available at most equipment rental outlets. With your carport’s base rails laid out and all caisson holes in place, you’re ready to install anchoring rods and fill each hole with concrete.
The concrete caissons should be allowed to set up overnight, before you continue assembling your carport.
Additional Carport Foundation Options
To learn about other foundation and anchoring options for your carport, consult the instruction booklet shipped with your carport kit, or give us a call at 1-877-833-3237.
NOTE – COLD WEATHER AREAS: If winters are severe in your area, there may be additional frost-line requirements for concrete foundations. Contact a contractor in the area, or your community’s building authorities for details.