How Much Does a 30×40 Concrete Slab Cost?

Building a barndominium requires a number of steps, one of the most essential being laying the foundation. If you’ve determined that the best way to go about building your barndominium foundation is by using a 30×40 concrete slab, you’ll obviously want to price out this important step in your barndo build.

Let’s take a closer look at budgeting this all-important element of your barndo build to get a closer estimate of the total cost of your barndominium!

How Much Does a 30×40 Concrete Slab Cost?

30x40 Concrete Slab - Foundation

The cost of a 30×40 concrete slab will depend on the vendor you go to, but generally, the price will range between $4 to $8 per square foot, with the median price being $6.

For a 1,200 square foot barndominium, this will mean that you’ll be looking at a total cost of $4,800 to $9,600, with a median of $7,200. 

However, like many things when building your own property, this is only an estimate, and there are a number of other factors which will influence how much you’ll be paying per slab. The approximate final price tag will depend on several things, including…

  • The lumber used for your wood form
  • The use or lack of fiber mesh inside the slabs
  • Whether you’re going to be laying the concrete yourself or hiring laborers to do the work.

Laying Foundations Using 30×40 Concrete Slab: Price Breakdown

30x40 Concrete Slab - Laid Slab

In terms of thickness alone, without accounting for labor, the cost of laying foundations using a 30×40 concrete slab breaks down like this:

  • 4-inch slab – $2.83 per square foot
  • 5-inch slab – $3.20 per square foot
  • 6-inch slab – $3.57 per square foot

If you’ve determined that you need certain additional features for your concrete, here are the approximate costs of some of the other potential costs:

  • Thickened edges – $1 per square foot
  • Vapor barrier – $0.50 per square foot
  • Wire mesh – $0.40 per square foot
  • Site preparation – $0.60 to $1.25 per square foot

The first three items on this list are all things that, though optional, will go a long way in strengthening the foundations of the concrete.

With thicker edges, for example, will improve the home’s overall structural strength, and is highly recommended when you’re planning to build a two-story barndominium.

While concrete slab edges can be poured up to two feet deep, the more common 12-inch edges are perfectly functional, and cost around $1 per square foot.

Vapor barriers work to limit the amount of built-up moisture and condensation beneath the foundation, which is a common cause of cracks and other structural issues.

Vapor barriers are recommended for any kind of structure that’s intended to be lived in, especially if you’re building in a particularly humid area. This feature will add approximately 50 cents per square foot.

Wire mesh, sometimes called wire fabric or wire cloth, can be used to reinforce your concrete.

This method of laying concrete has an advantage over rebar concrete in that it allows a certain degree of flexibility when shaping the concrete foundations which you won’t get with rebar. Wire mesh is available in various compositions, including plain, galvanized, and stainless steel, the latter two of which are especially resistant to rust.

Though the last item on this list, site preparation, should be completed before you actually start pouring the concrete, and is generally treated as a separate stage altogether, there may be additional work past the basics required, such as uprooting tree stumps or grading the soil where you’re building to make sure it’s totally level.

Some of this can probably be completed by you, but others will require the attention of experienced construction workers.

Determining the Cost of your 30×40 Concrete Slab

30x40 Concrete Slab - Setting
A residential concrete slab foundation with roughed-in plumbing and radiant floor heating tubes. The floor heating system can be water or propane.

To determine the overall cost of your 30×40 concrete slab, you’ll first need to determine whether you’ll be hiring contractors for the job, or if you’re capable of taking a DIY approach.

If you choose the latter option, you’ll only need to budget for the material and tools.

For a 4-inch thick slab of concrete alone, the average cost will be $2.83 per square foot.

From there, if you opt for features like a vapor barrier, thicker edges, a wire mesh, or other reinforcements, this will increase the cost to approximately $4.73 per square foot.

With all things considered, the total cost of material will range between $3,396 and $5,676 depending on the options you settle on.

If you decide on outsourcing the work to a contractor, on the other hand, you’ll also need to think about the cost of labor, which can add several more dollars to the cost per square foot for your foundations.

With contracted labor, the cost of laying a four-inch slab will generally range between $6 and $8 per square foot, meaning a total price range of $7,200 to $9,600. 

Bear in mind though that like anything, the price will vary depending on where you’re buying materials and hiring work, and in some areas, the cost of construction labor could be higher.

Wrapping Up…

We hope you find this price guide on 30×40 concrete slabs useful as you plan out and build your barndominium. For more guidance on building your own barndominium, be sure to check out barndominium insurance and the state guides, floor plans, design software for your floor plan, and featured homes on Barndominium Homes!