Once you’ve chosen where to set up a steel building, it’s time to prepare your site.
If you’re planning on putting your metal building or carport on an existing concrete slab, you usually won’t have to deal with this provided the slab is thick enough around the edges. If so, about all the preparation you’ll need is a bit of sweeping, or perhaps hosing away any dirt or dust.
If what you’ve got is bare ground, preparations are just a bit more involved. But not much.
METAL BUILDING FOUNDATION OPTIONS
Most steel buildings and carports are meant to be set up on any one of three foundation types:
- Prepared Ground – soil that has been leveled out and compacted or has good natural compaction.
- Concrete footing – strips of concrete, one under each side of the building, normally 12” wide, and 12” to 16” deep, and usually strengthened with steel reinforcing bar (“rebar”). [See illustration "Steel Building Footing" below]
- Concrete slab with a built-in footing – a slab, usually 4” thick, poured to form a complete floor for your building, with a footing underneath. The footing and slab are poured at the same time; you often hear this called a “monolithic pour.” [See illustration "Steel Building Slab and Footing" above]
Before starting your project, it’s best to check with your local building officials to find out what kind of a frost line you have. Your footing depth may need to be adjusted accordingly.
No matter what type of foundation you’ll be using, it’s a good idea to start by clearing off a level area 3 or 4 extra feet wide, all around the building’s location. This will give you room to work, and make it much easier to set up ladders when it comes time to install roofing and siding.
Preparing an area of ground for a building is fairly simple – all you’re trying to do is create a smooth, level, firm surface.
First, you’ll need to remove any vegetation, rocks and debris. This is strictly shovel and rake work. You might need a pickaxe to dig out more stubborn rocks or roots.
Next, you’ll need to make sure the ground is level. For this you can use a long construction level, or a smaller level placed on top of a long, straight piece of wood or steel. If you want to get fancy (and very accurate) you can use surveyor’s tools such as laser levels and surveying rods.
Once you have the ground reasonably level, it may need to be compacted to create a firm surface. In some cases natural compaction will suffice.
Compaction equipment such as rollers or tampers may be needed to achieve a good, firm surface. These can usually be rented from local equipment rental shops, and often from home improvement stores, too.
If you are using footings alone as your foundation (also known as “ribbon footings” or “strip footings”), they should generally be 12” wide by 12” deep, or 12” wide by 16” deep, subject to your frost line requirements, if any. Check local building codes, and the Absolute Steel instructions for your building, to work out the exact dimensions.
Footings should be positioned according to your building’s design. Some systems call for a footing that extends outward from the building’s walls, both inside and outside. Other systems work best with a footing that’s flush with the outer wall. In any case, your footings should be level.
Slab plus Footing
If you will be pouring a slab for your building, it should be at least 4” thick, with reinforcing bar (rebar) or fiber mesh reinforcement, and a perimeter footing.
Footing size and depth depends on local building codes. In most areas, a footing 12” wide by 12” deep will do – and the thickness of the slab (4”) can be counted as part of the 12” depth. In some areas, you’re required to have a footing that extends 12” below the frost line – again, consult your local codes.
Two continuous runs of #4 steel reinforcing bar are recommended in the footing – one running 3” from the top, the other 3” from the bottom.
The slab should be level, side to side and back to front.
With your foundation complete, you’re ready for the main event – putting up the building itself.
For more information on concrete requirements and/or ground-mount installation, use the links below…
- Metal building concrete requirements
- Garage kit concrete requirements
- Carport ground installation information
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Written by: Robert Armstrong