Concrete Foundation

Metal Building Foundation Note: Through the years we have seen many sets of engineered plans for our buildings come through our offices. This has given us the opportunity to examine different concrete and foundation requirements for many different parts of the country. While we have attempted to provide you with accurate information that will apply to your new building, we cannot guarantee it to be what an engineer would specify for your unique circumstances. What you read here is intended as a guide.

Our metal buildings can be anchored to a concrete footing or slab, or directly to the ground.

COLD-WEATHER AREAS – SPECIAL NOTE: The concrete applications described below do not account for frost line requirements. If you live in an area that has colder winters and a frost line, your concrete footings will need to be approximately 12″ below that line. Your local building authorities can provide information on frost line requirements in your area.

Site Preparation – for information on site preparation, click here.

Concrete Slab Mounting

We highly recommend that you anchor your metal building to a concrete foundation. This is a stronger method of anchoring, and it will most likely be required in order to obtain a building permit. The choice is ultimately up you, though. Our website provides additional information on metal building plans and permits, which should be useful in making your decision.

Size Your Slab: You should make your slab the same width as your building, and 2″ longer. For example, if you have purchased a 20′ wide by 40′ long building, your slab should be 20′ wide by 40′ 2″ long.

Concrete Floor: Your floor should be a minimum of 4” thick. The concrete’s strength should be a minimum of 2500 psi, with fiber mesh reinforcement added at the batch plant OR #3 rebar on 24” centers. If you are planning to park large, heavy vehicles inside (such as trucks or larger RVs), you should consider making the slab 6” thick, and using 4000-psi concrete. Be sure to saw-cut expansion joints in the slab, within an appropriate time after the pour, or trowel in expansion joints during the finishing steps.

For the sake of estimation, we can tell you that in our local area, the cost for a 4″ slab runs about $4.50 per square foot. Prices in your area may be different.

Footing Requirements:

(International Building Code 2006 or “IBC 2006” requirements)

At the same time as your slab is poured, you will also need to pour perimeter footings, as illustrated below. This is called a “monolithic pour” or “monolithic slab.”

Perimeter footings should be 12″ wide, and 12” deep. You can include the 4” slab thickness in the 12″ total depth; in other words, the footing would extend 8″ below the slab. As shown in the detail drawings, your footings will also need continuous runs of #4 rebar along the top and bottom.

In our local area, footings of this type would cost approximately $11.50 per lineal (running) foot.

Ground Mounting with Concrete Caissons

If you plan to construct your building directly on bare ground, rather than on a concrete pad or footing, you will need to dig post holes approximately 10” in diameter and 30” deep, every five feet along the length of the building. (If you have purchased a 4′-on-center frame building, the holes should be placed four feet apart.) Each hole will be filled with concrete, to form a “caisson.”

Assemble your base rails and lay them in place, marking where each hole should be dug.

Next, using a post hole digger or auger, make your holes 30” deep. Clean out the holes. Next, lay out your base rails according to the instruction booklet shipped with your building kit, and drop a ground anchor into each hole. Fill each hole with 2500-psi concrete (pre-mixed bags or mix your own). Let the concrete cure overnight before moving on with building assembly.

REMINDER: There may be additional frost line requirements in your area, which would make it necessary to make your footings or caissons deeper than indicated here. Your local building authority can provide you with information on this point.

Need more information? Feel free to call us toll-free at 1-877-833-3237