Every building, including a pole barn, needs a foundation to prevent settling and avoid uplift. A pole barn foundation generally uses pressure-treated columns that sit in holes in the ground backfilled with concrete.
You can also use other types of foundations. For example, options include slab on grade with brackets, perma column, sonotubes and bracket foundations.
When to Pour the Concrete Slab
You should not pour your concrete slab before you build your pole barn. Instead, set the poles first. Then place skirt board around the perimeter of the poles. That way, you will have a form for pouring your concrete.
Crews normally pour concrete through the large door opening. If you need more access, you can leave some wall metal off until the concrete goes in.
Fill and Slab Thickness
The fill beneath a concrete slab determines its strength and quality. So if the site drains well and has good compacted fill, a 4 inch thick slab should be enough.
Also, build your pole barn as soon as possible after you set the poles. That way, they do not warp or twist.
Building on an Existing Pole Barn Foundation or Slab
Do you have an existing foundation or slab? Then the easiest and least expensive approach is to cut holes through it and embed the posts in the soil.
If you would rather not do this, you can mount the pole barn to the concrete. However, a building inspector must first decide that the concrete can support the load. This means hiring a building inspector and possibly also an engineer.
What About Concrete Cookies?
A “cookie” is a pre-cast chunk of concrete that is 4 to 6 inches thick. It measures 12 to 16 inches in diameter. Builders put cookies in the bottoms of holes under building columns. They use them in designs with gravel, sand or soil backfill around the columns.
However, a pole barn foundation does not require cookies. That is because they are not large enough to spread the weight of the pole barn without settling, except in the smallest spans and the lowest loading conditions.