Concrete or Ground: What Should Your Metal Building Sit On?

You can put a metal building on bare ground, on gravel, on an existing concrete slab, or on asphalt. All four work. They cost different amounts, they take different amounts of preparation, and they suit different uses.

Here's how to decide.

The question behind the question

People usually ask "do I need concrete?" when what they actually want to know is one of two things: will the building stay put, or what am I going to be standing on in there.

Those are separate issues, and only the second one really pushes you toward a slab.

A building is held down by anchors sized for whatever it sits on. That part is handled either way. What changes is the floor.

Bare ground

The cheapest and fastest option, and the right one for a large share of open carports.

It suits you if you're covering vehicles, equipment, hay, firewood, or a boat, and you don't plan to work in there or enclose it later. Site preparation is minimal — the ground needs to be reasonably level, and that's about it.

The downsides are the ones you'd expect. You'll have dirt or grass underfoot, mud after rain, and you can't roll a jack around on it.

Gravel

A middle option that solves most of what people dislike about bare ground, for a fraction of what concrete costs.

Gravel drains, keeps mud down, and gives you a firmer surface to walk and work on. It's a common choice for equipment storage, for buildings that will be open on at least one side, and for anyone who wants a usable floor without a slab budget.

It still isn't a floor you can sweep, and it won't take a floor jack.

Concrete

A slab is the right answer when any of these apply:

• You're enclosing the building. A closed building with a dirt floor traps moisture. Ground damp has nowhere to go, and it ends up on whatever you're storing.
• You want to work in there. Rolling toolboxes, jacks, and anything on casters need a hard flat surface.
• You're storing something you care about. A classic car or a restoration project belongs on concrete.
• You want to finish the interior later. Insulation, lighting and shelving all assume a slab.

The tradeoff is cost and time. Concrete is poured, then cured before anything goes on it, and it's usually the largest single line item in the whole project.

Asphalt

If you already have an asphalt driveway or pad in the right spot, a building can go on it. This mostly comes up when someone wants to cover an existing parking area rather than create a new one.

What matters more than any of this: level

Whatever surface you choose, the spot has to be level. That's the requirement that actually determines whether installation goes smoothly.

A site that slopes noticeably needs grading, fill, or a retaining edge before anything can be installed, and that preparation costs money regardless of which surface you picked. It also has to be sorted out before installation rather than during.

If your spot isn't level, deal with that first and decide about concrete second. Tell us about the slope when you request a quote and we'll tell you what it'll take.

If you're going with concrete, order in the right sequence

The slab has to match the building, not the other way around, and the dimensions aren't always what people assume. Get the building specified first, then pour to those dimensions, then schedule the install for after the concrete has cured.

Pouring a slab before you've settled the building size is how people end up with a pad that's four inches too narrow.

Permits

Some counties require a permit for a metal building and some don't. It can also depend on the size, on whether you're pouring concrete, and on how close you are to a property line. Requirements vary enough across North Carolina that the only reliable answer comes from your own county's inspections office.

We can handle the permit filing for you when one is required, for an additional fee.

The short version

Most people who go straight to concrete are enclosing the building. Most people who are only covering a vehicle do fine on ground or gravel and would rather put the difference toward a bigger building.

Not sure which way to go? Build your configuration on our estimator to see where the price lands, then tell us about your site when you send it over. Quotes are free and there's no obligation.