Build your pole barn on a solid foundation so it stands as strong as you do
When selecting pole barn foundation options, choosing the right one can add years to the lifespan of your post-frame building—saving you money and headaches. As with any building, a solid foundation is essential. In this article we’ll discuss a few different pole barn foundation options and what factors may make one of them the right option for your building. Always check your local building codes to find out what types of pole barn foundations are allowed.
This one is typically precast concrete, about 12 to 16 inches in diameter and at least 6 inches thick. One of the most cost-effective options, concrete foundation pads rest on compacted crushed stone. With a pole barn, you’ll want something more substantial than a smaller shed foundation that consists of only a concrete slab, for example. A pole barn should have a foundation that goes at least 48 inches below ground (or grade).
As with any foundation type that goes below grade, concrete pads should be placed at least 48 inches below ground. This ensures they’re below frost level to prevent frost from getting underneath and heaving or moving your foundation. You can accomplish this in a couple of different ways.
Auger holes down at least 4 feet below grade, making sure to go deep enough to place at least 6 inches of crushed stone at the bottom and still have the pad 4 feet below ground level. Place the stone, compact it, and place the concrete footing pads. After placing the posts, backfill with crushed stone for drainage to keep water from resting against the wood.
Rather than augering holes, dig a 12 to 18 inch wide trench. Place at least 6 inches of crushed stone in the bottom of the trench. Compact the stone and then place the concrete pads on the stone. After setting the posts, backfill the trench with crushed stone.
In both instances, wrapping the crushed stone with a landscape fabric (so the fabric is between the soil next to the crushed stone) will help keep the soil from washing into the stone, ultimately defeating the purpose.
With wood posts below grade like this, every precaution must be taken to ensure good drainage so water does not rot the wood. The area around the post should also be backfilled with crushed stone for good drainage.
| Pros | Cons |
|---|---|
| Environmentally friendly | Expensive |
| Low maintenance | Prone to cracking |
Best For: Areas with clayey soil
Another option is to encase the below-ground part of the posts in concrete. This is done by digging or auguring the post hole in the same way as with the concrete pads. This time, you’ll place the post into the hole on the crushed, compacted stone and pour concrete into the hole to encase the wood post. It’s important to ensure that water does not get trapped between the concrete and the wood posts. Using a circular form to continue the concrete above ground will help keep water from resting on top of the concrete and running down between the post and the concrete.
Make sure the concrete cylinder is the same diameter all the way up. Any concrete overhanging can get caught by the frozen ground and pushed upward, possibly causing major damage to your pole barn. Additionally, the foundation may not settle down again when the ground thaws, as the soil can fall down under the bottom of the concrete column.
| Pros | Cons |
|---|---|
| Affordable | Posts can rot if not sealed properly |
| DIYable | Can result in settling issues if done incorrectly |
Best For: Sandy or loose soil
If you ever have any posts rotting below ground, it can be difficult and costly to make repairs. Some builders prefer to keep all the wood posts above ground. To avoid burying the wood posts (and potential foundation repair costs down the road), you can use a couple of different types of brackets that fasten the bottom of the posts to the concrete foundation.
This type of bracket is fastened to the concrete with bolts designed to be used with concrete and masonry. A pilot hole is drilled into the foundation, and then the special bolts are installed. Standard lag bolts are used to fasten the bracket to the posts.
Another type of bracket gets set directly into the wet concrete. The part of the bracket above the concrete looks and works the same as the drill-set bracket. These kinds of brackets make it easier to monitor the condition of your wood posts and to make any repairs. It’s still important to protect the wood posts from water, though. But this type of bracket is the stronger option if you want to use brackets because the bracket is placed directly into the concrete rather than fastened to it.
| Pros | Cons |
|---|---|
| Avoids rotting posts below ground | Not the strongest option |
| Easy to perform repairs | Prone to settling |
Best For: Uneven terrain
Rather than running wood posts into the ground where water can possibly rot them without you knowing until it’s too late, you can use precast concrete columns resting on concrete pads and fasten the posts to the top of them. The columns are typically made using 10,000 PSI concrete (whereas standard concrete slabs are 3,500 to 4,000 PSI) and are reinforced with steel rebar that’s welded to a steel plate or bracket.
| Pros | Cons |
|---|---|
| Easy to install | Can lose level from shifting soils |
| Long-lasting | Expensive |
Best For: Areas with cold climates
This option is the most costly and requires a bit of knowledge on how to pour a foundation, but it is also the best option for longevity and strength. Typically, concrete is poured into a 12-inch wide, 48-inch deep trench up to grade, and then the pole barn is built on top of that. If you’re building a larger pole barn, this option may be worth the investment. Local codes may also require this type of pole barn foundation for certain buildings of certain sizes.
| Pros | Cons |
|---|---|
| Longevity | Most expensive |
| Strength | Requires expertise |
Best For: Areas with sandy soil
Although the building codes in your area have already considered these factors and established codes accordingly, many areas have a variety of soil types and water table depths that can allow for some choice of foundation type.
If you live in an area with sandy soil, you may want a continuous poured foundation to ensure that your pole barn is built on the sturdiest foundation possible. If the ground has a lot of clay, concrete pads may be sufficient. If you’re not sure, you may want to call a local foundation contractor for advice and an estimate. After all, this type of work isn’t DIY-friendly unless you have the equipment and the experience.
"The type of soil your home sits on is crucial for foundation stability. Clay soils expand and contract with moisture changes, which can lead to foundation movement. Sandy or well-drained soils are generally more stable. If the soil isn’t ideal, you might need to take extra measures like soil stabilization or proper drainage systems to prevent shifting and settling."
— Tim O'Shea, The Build Pros
As you can imagine, the weather you see throughout the year will help determine the best foundation choice for your pole barn. If you get a lot of rain or snow, your posts are more likely to rot from the moisture, and you may want to consider pole barn foundation options that keep your posts above ground.
No matter what foundation or footing method you choose, protecting your posts from moisture rot and insects like termites is vitally important for the longevity of your building and to protect your investment in the cost to build your pole barn. Companies make special waterproof sleeves and wraps to help keep the posts dry for buildings with wood foundations. Wraps like this typically run from the bottom of the post to a few inches above grade or above your pole barn floor.
There are a few different types of foundations that are good for a pole barn house. Concrete pads, brackets on concrete, and posts set in concrete-poured columns are a few of the best options.
Whether pole barn posts should be set in concrete depends on the soil surrounding your home. If your soil is compact and digging conditions are agreeable, then setting pole barn posts in concrete is an ideal option.
Your foundation contractor will first need to remove the topsoil and any vegetation within 4 feet of the area around the barn. They’ll need to ensure they have clear access to the site to begin excavation, after which they can begin construction.
The foundation for a pole barn should be at least 36 inches thick to ensure that the piers won’t shift from frost heave.
