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Foundations for steel arch buildings and garage kits.

A good foundation is important to the overall integrity and life of your steel arch building. Here is what you need to know about foundations for your metal garage kit.

Preparing the foundation site
The first step after acquiring a building permit and making sure your plans are in accordance to local building codes is laying a proper foundation is to have the site your structure is going to be erected on is level. Have the land which your steel arch building is going to be erected on is surveyed and the boundary points are established. Once this is marked off the next step is grading the land and making sure the entire surface plane shape is level and the height is uniform.

The next step is grading the site. Have the site inspected to evaluate soil conditions and moisture problems. Drains may be installed in circumstances where excess water around yet building needs to be redirected. They can be as simple as adding a french drain on the perimeter. But in most cases you won’t have to worry about this. The soil that lies under the foundation may need to be replaced so that adequate drainage and stability can be achieved. Again, a professional can advise you on the quality of drainage and soil. Grading the site will make the surface level so you are prepared for excavation of the area used for the foundation.

Consult with your Metal Building Kings® representative as to how deep the excavation should be for your particular steel arch building model and size. Most metal garage kits for residential use require only modest excavation depth vs. a large industrial size arch building that requires more depth. You can choose to use hand tools to dig out your foundation base or commercial rental equipment such as a skid steer loader or track loader which is perfect for a home improvement project such as foundation excavation and a electronic self-leveling rotary laser level works well for leveling accuracy. Your foundation should slope 1/8” for foot towards your end wall overhead doors for adequate interior drainage.

Selecting the correct type of foundation
A Monolithic / Floating slab - This foundation is a concrete slab that sits on top of the graded soil trench. For most garage kits this type of slab is suitable. In severe cold climates the slab will need to be deeper than the frost line (5-8 feet below the surface) to prevent the ground from pushing up the foundation and creating a frozen gap underneath that eventually thaws and causes to foundation to resettle again repeatedly each season. This can cause cracks in the foundation and damage the integrity of the building’s structure over several years.

A 3-4 foot foundation can last decades but will eventually crack in the middle. Chances are your building won’t be affected by minor cracks. If you are concerned, one solution is keeping the building warm in the winter so the heat is transferred through the cement floor to keep the moisture underneath the foundation from freezing.

Another solution is Frost-Protected Shallow Foundations that are insulated protecting the dement from frost heaves.

What we have found to be most effective for heated or non heated arch building kits is having the concrete slab placed higher than the surrounding ground around it and have it thickened to 2’ around the perimeter and insulated on the outside face. This is commonly known as the “Alaska Slab”. One customer created his own creative solution by adding radiant heat with PEX heat pipes tied to wire mesh inside of the concrete pour.

pier and beam foundation

Pier and Beam Foundation
This type of foundation is impervious to severe cold and frost heaves.
The “pier” is a concrete column that goes deep into the ground and sits on solid rock which cannot contract or expand. The piers are aligned and placed throughout the span of the foundation. The concrete “beams” sit on top of the graded site and on top of the piers just like roof trusses in your house sit on the vertical walls. Below the grade beams are voids of space that soil in that area to absorb water too it doesn’t expand and push up on the beams causing cracks in the foundation. This is the best foundation for larger steel buildings.

In both cases it is advisable to layer steel rods in the concrete foundation to increase the tensile strength. Use a 2:1 ratio of sand to cement and a 2:1 ratio of Coarse Aggregate to sand to get a 3,000 PSI foundation. Always add admixtures which are a water retardant additive to strengthen the curing process.


The concrete pour
Construct solid perimeter forms with ridged wood and brace the forms to keep them in place. Once the mixture is created it must be kept in motion with a rotating drum to keep the aggregate mixed in uniform throughout the mixture and avoiding air pockets. Screed the concrete before it dries by pushing the cement to fill in gaps to have a smooth level surface. Then place large heavy wood planks on top of the surface to keep large stones from popping up above the surface and compacting the dement to assure a hard consistent surface.

If you need assistance in coordinating with outside contractors to plan and pour your foundation, we provide turnkey solutions coordinated with local contractors to assist your with planning and constructing the right foundation for your geographical area and climate.

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