How Much Does a 30×40 Concrete Slab Cost? [With Thickness]

When building a barndominium, several costs must be considered.

While it is essential to evaluate the cost of framing, flooring, or plumbing, the first and most important expense to determine is the cost of building the foundation.

Since many barndominium home builders recognize this fact, it has led to many asking how much does a 30×40 concrete slab costs for a barndominium?

The average cost is $5.50- $9.50 per square foot. The median price is about $6 per square foot. Based on this price range, you can expect to pay $6,600- $11,400 for 1200 square feet.

It is worth noting that this is an average and the actual price will differ based on what the slab includes and a person’s state laws on the cost of labor and materials.

What Is A Typical 30×40 Concrete Slab Made Of?

A 30×40 concrete slab will cover 1200 square feet. One may need to spend $5.50- $9.50 per square foot; this would mean an estimated $6,600- $11,400.

It is worth noting that this estimate depends on the following options:

  • 3000 PSI Concrete: PSI is used to measure the compressive strength of concrete. As a rule of thumb, the higher the PSI, the more durable the concrete. Concrete slabs typically require a concrete of 3500- 4000 PSI. However, if one goes for a higher PSI, then they will pay more.
  • Six Inches Thick Concrete: The thicker the concrete, the more weight it can support, and of course, the more expensive it is. Be prepared to shoot for tens of thousands of dollars for a concrete thicker than six inches.
  • Fiber Mesh: Concrete mesh is ideal for slab reinforcement. There are two types of concrete mesh: fiber mesh and wire mesh. Both of them are used in reducing cracking and structural damage. Fiber mesh is generally cheaper than wire mesh and easier to lay.
  • A Double Row Of Rebar Around The Edges: A rebar (reinforcing bar) is a bar used for strengthening and reinforcing the cement under tension. Rebar comes in different sizes, grades, and types. The one included in your slab may make it affordable or on the high side.
  • Concrete Curing Compounds: Curing compounds help to reduce the evaporation of water from the concrete, thereby preventing shrinkage and cracking. If these options are included, it will impact the cost of a concrete slab.
  • Concrete Anchor Bolts: Concrete bolts are mainly used to attach steel to concrete. It connects the steel to the concrete while providing structural support.

Other features may include;

  • Labor to form the edges
  • Labor to power trowel
  • Sawed contraction joints

How Much Does a 30×40 Concrete Slab Cost?

As previously explained, the cost of a 30×40 concrete slab depends on the materials used in making the slab.

A slab made with more durable materials and added features will cost more than a concrete slab with fewer features.

Typically, the average cost is $5.50- $9.50 per square foot while the median price is about $6 per square foot.

How Much Does a 30×40 Concrete Slab Cost

If construction workers are hired for the job, then the local labor rate in the specific state must be considered.

A construction timesheet software like Raken allows workers to record how much time they have worked. This keeps the employer from overpaying or underpaying.

The size of the concrete slab will also play a major role in how much is spent.

The cost of two 30×40 slabs will still differ depending on thickness, built-in reinforcement, finishing type, and grade of concrete

Since the price of concrete slabs depends mainly on their features, it makes sense to know these features and how they impact the price.

The following paragraphs break down the standard features and their costs.

Cost By Slab Thickness

Concrete slabs fall in the thickness range of 4-6 inches. Concrete driveways can go up to 8 inches as they need to withstand higher tension.

Anyone going for a concrete slab with 6 inches can expect to pay more than someone settling for a 4 inches slab.

The price is thus by the square foot;

  • 4 inches – $5.35
  • 5 inches- $5.78
  • 6 inches- $6.19

Cost By Reinforcement

Reinforcing a concrete slab enhances its durability, quality, and longevity. Added features for durability like wire mesh, rebar, or fiber mesh can significantly impact the cost of a concrete slab.

A plain concrete slab may cost $5.50- $6.60 per square foot. After installing reinforcements, the price can go up to $9.29-$10.04.

Reinforcement options and their cost per square foot include;

  • Installing wire mesh – $0.35
  • Installing vapor barrier- $0.50
  • Increasing Edge Thickness- (12inches- 2feet)- $1.00- $1.75
  • Styrofoam (2 inches)- $1.25
  • Installing Fiber Mesh- $0.13
  • Installing Rebar- $0.75- $1.40

Cost By Slab Finish

Many homeowners do not like the gray, dull look of concrete slabs. Therefore, they may want to give their slabs a decorative finish.

It is worth noting that doing this will add to the pricing.

Some finish options and their costs include;

  • Polish- $3.00 to $7.25 (Low end) $14 to $30 (High End)
  • Stained Concrete- $3.40 to $9.75 (Low End) $25 (High end)
  • Epoxy- $4.75- $10.00
  • Stamped Concrete- 9.00- 16.25 (Low End) 25.25 (High End)

See AlsoHow Much Does a 24*24 Concrete Slab Cost?

30×40 Concrete Slab: Determine Your Cost

Before asking, how much does a 30×40 concrete slab cost? There are some decisions one will need to make.

For instance, a person will need to decide whether to hire a contractor or if it will be a DIY project.

Both options hold their pros and cons. Hiring a contractor will cost more.

You may need to cover labor expenses which may add a few dollars per square foot to the original cost.

Hired labor will increase the price of a 4 inches slab from $5.35 to $6- $8 per square foot. This may result in a total price range of $7,200- $9,600.

It is worth noting that the cost of labor and materials, however, depends on the region a person resides.

One may also decide to tow the DIY line. This decision may save one a lot of money or become a big mistake.

If a person is pouring the concrete by themselves, they will only need to spend money on materials.

Depending on the reinforcements added to the material, the person may need to pay between $3,396- and $5,676.

How Is Slab Cost Calculated?

The math can be quickly done using an online calculator.

Below are the results from an online calculator of the estimated costs for a 30×40 concrete slab using an average cost of $6.88, $10.47, and $14.61.

The difference in cost range depicts the quality of materials and job.

Regular Better Best
Material prices for Concrete Slabs. $2220.00






The Installation cost for Concrete Slabs. $5400.00






Total cost for Concrete Slabs. $7620.00






Total Average Cost per square foot for Concrete Slabs. $6.88 $10.47 $14.61

How Much Does a 30×40 Shop Cost?

The price of a 30×40 shop depends on the location of the building, its specifications, and upgrades. The average kit costs $1500.

However, it can vary greatly and range between $13,000- and $24,000. Materials for a 30×40 shop will set one back $17.22 to $19.44 per square foot.

Since a 30×40 shop allows 1200 square feet of usable space, one can expect to pay $20,664 to $23, 328.

How Much Does a 30×40 Shop Cost

The construction cost will also vary depending on a person’s state laws. Generally, it may cost between $6-$8 per square foot giving $5800- $10,600 for a 1200 square foot interior.

All in all, a basic 30×40 shop will cost anything from $30,264- $42,528 to build.

The more customization and designs one adds, the higher the price goes.

Have A Look: How Much Does a 30×30 Concrete Slab Cost for A Barndominium?

How Much Concrete Do I Need?

To accurately calculate slab cost, one must know how much concrete one will need for the project.

The tools required for this are a measuring tape, pencil, paper, and a calculator.

Then, follow the steps below;

  1. The first thing to do is estimate the volume of concrete needed for the job. Measure the dimensions (length, width, height) and quantity of the area to be paved.
  2. Determine the weight of the elements. To do this, calculate the volume of concrete and the density (Information will be provided on the concrete bag)
  3. Find out how much concrete is produced per bag and calculate the waste or spillage ratio- this could be 5-10%


If one has four concrete elements and each of the elements is 3 feet long, 3 feet wide, and 3 feet high. Most pre-mixed concrete is sold by the cubic yard.

And construction elements are measured in feet. For instance, four cubic yards will measure 108 cubic feet.

A person may know how many concrete slabs they want, or they may know the area that needs to be paved.

If a person wants to pave a 36 square feet area, they would need four cubic yards of cement in bags weighing 150Ib/cu ft density.

The total weight of the concrete the person will need is 16,201.03Ib. Suppose they include 5% for spillage, that means, they will need 284 bags of concrete.

Concrete Slab Cost Calculation

Multiply the square footage by the depth of the slab and divide by one cubic yard( 27 square feet). For instance, a 10×10 concrete slab will need 1.3 yards of concrete.

The math will look thus: [(10×10×.33feet)/27].

The average thickness of a concrete slab is 4 inches. If a person’s slab is more than 4 inches, they should calculate the depth they intend to use.

Ensure to translate the slab’s thickness from inches to feet before using the above equation.


As the reader already knows, the cost of a 30×40 concrete slab can go from  ‘affordable’ to ‘pretty expensive’ depending on the features the user wants.

Also, the region where a person lives will impact the overall cost. This is because materials and labor are more expensive in some areas than in others.

So, how much does a concrete slab cost for a barndominium? This guide gives a rough estimate.

James HallBarndominiums Advisor

I'm James, your barndominiums advisor. Several years ago, I had no idea what barndominiums were. Although I'd spent over 10 years in the construction industry, the first time I heard about barndominiums was when I saw my neighbor building a new-style home. That was the first barndominium I've ever seen, and I found it so fascinating that I wanted to learn more about them.

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