Reliable Pole Barn Foundation Options - Michigan Building Design

Traditionally a pole barn foundation is simple footings with wood posts extending below the frost line. However, depending on your location, application, and comfort level, your pole building plans may specify a different type of foundation.

You may have a larger building that requires more concrete, or you may want to install in-floor heating. A licensed structural engineer can tell you what kind of foundation is best suited for your building, but it can be helpful to have a basic understanding of the various options.

In this post we’ll talk about the pros and cons of each foundation type.

Here are your main pole barn foundation options (click to jump to section):

Post in Ground
Concrete Piers (Permacolumns)
Cast-in-Place Piers (Sonotubes)
Monolithic Slab Foundation
Stemwall Foundation

Concrete Foundations Require Brackets

Before we jump into foundation types, there’s a common factor among concrete foundations. If you’re not using a post-in-ground foundation, then you’ll need brackets to attach your posts to the concrete.

There are two options: you can use wet-set brackets during the concrete work, or drill-set brackets (also called dry-set brackets) after the concrete has set.

Wet-set brackets typically have a deep rebar anchor system that allows you to take advantage of the strength of post frame construction with a concrete foundation. These brackets use welded rebar set into the foundation to transfer the loads properly into the foundation. They’re stronger and better.

We do not recommend drill-set brackets, since shallow masonry drilling significantly effects how the structure handles the bending moment. The lateral bracing or sheathing required to make the building function with a drill-set bracket vs. a wet set is very different. From a cost-benefit standpoint, drill-set brackets typically do not make sense for a new build.

Now let’s break down the pole barn foundation options.

1. Post in Ground

Properly treated wood columns set on solid footings, buried below the frost line, provide the bulk of the structural integrity of a pole building. This is an affordable, relatively fast, and easy way to build accessory buildings and storage buildings. There’s a reason post-frame construction is so popular!

Some people prefer to avoid post-in-ground because they are concerned about wood rot, and subsequently pole barn collapse. With a properly prepared site and properly treated wood, post decay is almost unheard of. Read more about it here.

Post-in-ground pros:

Most affordable option
Fastest install
Minimal concrete work
Very simple – no brackets, bolts, etc

Post-in-ground cons

May not be adequate for commercial or large barndominium-type applications
Has potential for rot in unprepared soils

2. Concrete Piers or Permacolumns

If you’re really against putting wood in the ground, permacolumns are the way to go. These are very similar to post-in-ground foundations, except the post is made of concrete and rises to just above the grade. Connecting brackets fasten the wood posts to the concrete piers, creating a solid base for your pole building.

Permacolumn pros:

The most affordable of the concrete options
Minimal to no wood contact with the ground
Quick and easy to install
Easiest to finish cleanly, as the concrete post dimensionally matches the wood post

Permacolumn cons

More expensive than a wooden post in the ground
The concrete joint is visible on the interior of the pole building, which might not be the aesthetic you desire
May not be adequate for commercial applications

3. Cast-in-Place Piers (Sonotubes)

We are only including this on the list because it is popular with DIYers on Youtube. We would almost never recommend this type of foundation for a post-frame building.

Sonotubes work a lot like permacolumns, except instead of buying a pre-made product, you’re pouring the concrete yourself. After digging holes and pouring the post footings, you can use round sonotube forms to create cast-in-place piers.

A sonotube footing detail should include footing, the sonotube, and rebar reinforcement from the footing all the way up to the bracket. That’s the problem with the content that is currently popular on the internet: they may not reinforce the sonotubes, and some of them don’t even use footings!

Sonotube pros:

Probably about the same cost for materials as permacolumns

Sonotube cons:

Large round concrete columns stick up above the grade. This means it’s hard to finish the interior, exterior and slab in an aesthetically pleasing manner.
Requires multiple days of concrete work. Any material savings are offset by additional labor.
This method has many DIY resources available on the internet, but the structural integrity is questionable and may be very different for your intended application.

4. Monolithic Slab Foundation

A slab foundation requires significant site prep and concrete work, but it will keep all wooden components above ground. These foundations may make sense for commercial applications or barndominiums with in-slab heating. They are not the most cost-effective choice if another option will work.

They can be built above frost line if they’re continuously heated, with special consideration to the insulation. A slab doesn’t work well if the building is unheated due to the additional concrete required, but it is doable.

Slab foundation pros:

Concrete can be poured in a single pour – footings and slab are poured simultaneously
May be the best option for buildings that are to be continuously heated
Better continuous insulation options

Slab foundation cons:

In Michigan, if the building is not continuously heated footings must be below frost line. This uses a very large amount of concrete compared to the other options.
Significant site prep vs. other pole barn foundation options
Significant concrete work vs. other options
Additional material costs for lateral bracing

5. Stemwall Foundation

A stemwall foundation is commonly used for commercial applications, and may make sense for barndos and similar builds. It requires significant concrete work, with multiple pours and reinforcement. It may also require additional lateral bracing or sheathing as the posts are not using the soil to resist lateral loads.

Stem wall pros:

If you’re building a commercial building or barndominium or application that sees a lot of interior moisture on the floor, this may be a good option
Good insulation options
No wood anywhere near the ground

Stem wall cons:

Significant site prep
Significant concrete work in comparison to other options, requiring multiple pours
Additional material costs for adding lateral bracing in comparison to other options

Trust MBD To Determine the Best Foundation Type for Your Building

There’s a lot of information available about different pole barn foundation options. It’s not a one-size-fits all approach, which is why your best option is to hire a professional engineer. An experienced structural engineer can help you determine the most affordable, simplest option to fit the building you have in mind.

Michigan Building Design has worked on all different types of accessory buildings and post-frame buildings in our cold northern climate. If you want make sure your foundation and structure will withstand the snow loads and stresses of Michigan weather, give us a call at (231) 577-9523 or fill out our online contact form. We offer engineer sealed plans at reasonable rates.