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Can a Post Frame Building Have a Crawl Space?

Can a Post Frame Building Have a Crawl Space?

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Post-frame buildings have been around for years, and they’re built using wooden posts that are set on some sort of concrete foundation. That means post-frame buildings usually don’t have a crawl space or a basement.

However, concrete slabs aren’t the only foundation options. This brings us to the question: can a post-frame building have a crawl space? Keep on reading to find out!

Can a Post Frame Building Have a Crawl Space?

Yes, a post-frame building can have a crawl space foundation. However, that type of foundation will need proper site grading and an exterior drainage system.

You’ll also have to damp proof the exterior crawl space walls to keep any outside moisture from creeping into them.

That said, before deciding to have a crawl space foundation for your post-frame building, you should check with your local zoning and building office. They’ll help you confirm whether the location is suitable to build in and if your desired design is achievable or not.

Types of Foundations for Post Frame Building

Let’s take a closer look at the types of foundations a post-frame building can have:

1 – Floating Slab

Typically, post-frame constructions sit on a concrete slab foundation with the wall frame attached to the concrete through metal brackets. The concrete slab usually seals any piping and potentially electrical wiring systems.

While this method is common—probably because it’s affordable—it still has some disadvantages.

The major problem you might face with floating concrete slabs is plumbing-related problems. If there’s sewer drainage or underground water leakage, you’ll probably have to break the concrete to do the plumbing.

Plus, you’ll need to find an alternative space to install a ventilation system, unlike crawl spaces and basements.

2 – Wall Foundation

You can set the post-frame building on a wall foundation system to solve the floating slab plumbing problem.

This type of foundation uses concrete to build a wall layout that extends below the frost line. After the concrete sets, metal brackets are drilled inside the wall layout to hold the wall frame posts.

Aside from not having to remove concrete to do the plumbing, wall foundations ensure your building doesn’t get damaged by frost heave.

3 – Structural Columns

Instead of a concrete wall layout, you can also use separate column footings to set in the post frame building posts.

There are several ways to install posts in separate footings, including:

1 – Rebar Wall Bracket

Similar to the wall foundation, this type of footing uses a rebar wall bracket to hold the wooden posts. However, the brackets are set on the concrete column while it’s still curing.

The poured concrete gives a strong base for uplift resistance, ensuring the posts can handle wind forces. It also keeps the wood away from soil contact, thus protecting it from rot.

2 – Post on Concrete Pad

For this type of foundation, the post base is made of concrete to increase the posts’ strength.

A metal uplift bracket is attached to the post’s base and is set on top of a concrete pad. The concrete extends around a foot above the grade to limit wood-to-ground contact.

3 – Treated Post in Poured Concrete

Instead of using some type of anchorage to hold the wooden post, you can directly place it in poured concrete footings.

While the concrete will provide stability, still it can shrink and expand, creating a gap that holds water, increasing the chances of rot.

4 – Crawl Space

Typically, to have a crawl space foundation, you have to build a wooden wall framework of at least 18 inches or more above grade.

You then have to fill the wall framework with concrete—the concrete footing varies in thickness and width depending on the load.

While it’s uncommon to include a crawl space when constructing a post-frame building; still, those pint-sized basements can be practical.

For starters, it makes plumbing and electrical wiring much more accessible. You can also insulate it and use the crawl space as an air plenum space for better ventilation.

However, you might have to deal with problems like pests, mold, and accumulated underground water if you don’t insulate the crawl space properly. Plus, encapsulating a crawl space can be pricey.

Final Thoughts

So, can a post-frame building have a crawl space?

The answer is yes. Post-frame buildings can have different types of foundations and footings, including a crawl space.

Before deciding on having a crawl space foundation, you should check with your local zoning and building codes. That way you’ll know whether the type of soil is suitable for this type of foundation or not.

After all, building a crawl space on poor drainage soil can cause many problems that’ll cost you more to repair.


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