How Much Does a 20×20 Concrete Slab Cost?

If you are considering purchasing a barndominium to fit on this size concrete slab it would be approximately  20 feet wide and 19 feet 10 inches because you need the concrete slab to be two inches longer than the barndominium.

Now that we have figured out what size barndominium can fit on this size slab, how much does a 20×20 concrete slab cost?  Are there any extra fees to figure out in the cost?  How can you make concrete slabs cheaper? 

These questions and more will be answered in this article.  We will also tell just what you would get with that size barndominium so you can see if it fits your family.  Read on to learn about what it costs for a 20s20 concrete slab.  On average this size slab can cost $1,650-$3,300.

How Much Does a 20×20 Concrete Slab Cost – Important Factors

When figuring out the cost of a 20×20 concrete slab, there are several factors that you need to take into consideration.   When getting an estimate for the cost of the 20×20 concrete slab, make sure you get all the details in writing so you can do a comparison before you select the one for the job.

How Much Does a 20x20 Concrete Slab Cost

Duration of the Project

When figuring labor costs, they are generally figured by the hour and not by the job.  How long it will take to finish the job will affect how much is going to be added to the estimate.  Always check to see how many hours they figure it will take to complete the job.

Type of job

There is more to the job than just pouring the concrete, which will add to the cost.  Some of these include:

  • Removing old concrete—if you decide to have the concrete poured where there is old concrete it will have to be removed.
  • Pumping concrete—if it cannot be mixed on-site and has to be transported there will be a charge to pump it out from their concrete mixer into the frame.
  • Sealing the concrete—this is when they apply a sealant on the concrete slab to protect it from wear and tear and stains. The price will depend on the sealant that is used


Yes, you can mix concrete by hand but with such a huge slab of concrete to pour, they may have to use special machinery, suck as pump trucks or cement mixers.

You will also need to have a wood form that will hold the concrete while it hardens, and a fiber meshing inside the concrete to increase the strength of the concrete.  There is also the cost of the row of rebar that will be around the inner perimeter of the concrete slab.  The price will also depend on the thickness of the concrete slab.  If you do the project yourself, you will save money on the cost of labor.

Here is an average cost chart for a 20×20 concrete slab.  The prices are per square feet

Installed on average $2.468 for 400 sq ft.
Installed for 4 inches thick $5.35
Installed for 6 inches thick $10.55
Thicker edges from 12 inches to 2 feet $1.00-$1.50
Vapor barrier $0.50
2 inch Styrofoam $2.00
Wire mesh $0.35
Pump truck if the concrete truck cannot reach the slab $900 flat fee
Labor for 4-inch slab $2.52
Labor for 6-inch slab $2.60
Material for 4-inch slab $2.83
Material for 6-inch slab $3.57

On average, the cost of labor would be $45 per hour to pour your concrete.  There may also be a delivery fee, which can average $60.  The average cost for a 20×20 concrete slab would be $1.700 to $3,300 with labor being a larger portion of the cost.

How to Calculate Concrete

To figure out how many cubic feet of concrete you would need for a 20×20 concrete slab, you will need to find out three dimensions.  That is the length, depth, and width.  This formula is one of volume so that is why you need these three dimensions.

How to Calculate Concrete

Using a measuring tape, you will need to get all three of the above-mentioned dimensions and write them down.  If there are any measurements in inches you will need to divide them by 12 to the number of feet.

Measure all measurements together to give you cubic feet.  For example, if you were pouring footings for a 20×20 barndominium floor, you would multiple the length, which is 20 feet by the number of sides, which would be four.  And then multiply that by the width of the footings.  For example, if they are 16 inches, that would be 1.33 feet (16/12)   The area of the footings would be 20*4*1.33  Then you would need to multiply the footings depth for the volume of the concrete.

Once you have added up all the volumes you will divide that number by 27 to get the number of cubic yards.  You divide by 27 because there are three feet in a yard.  In a cubic yard, there are 27 cubic feet.  (3*3*3*=27).

A concrete truck will hold from seven to fifteen cubic yards of concrete.  To help determine how many truckloads will be needed for a 20×20 concrete slab, you would calculate how many cubic yards you would need.  One reason that you calculate in yards is that when buying bags of concrete, they are in cubic yards.  It is advisable that if you decide to do it yourself, you round up your calculations to the nearest half-yard.  This will give you extra concrete if you make an error in your calculations.  One cubic yard of concrete will equal approximately 3,600 pounds of concrete.  For example, if each bag of concrete weighed 50 pounds, it would take 72 bags of concrete but should get one extra to account for any errors in calculations.

What is the Cheapest way to Make Concrete?

The cheapest way to make concrete but can also be the hardest way is to do it yourself.  You can purchase your bags of concrete at a home improvement store.  On average, for a 50-pound bag of concrete, it would cost from $5 to as much as $34.  It depends on which store you purchase it from, the brand,  and if it is rapid or quick setting concrete.

With mixing your own, all you would need is a wheelbarrow or something to mix it in and then carry it to the site to pour it along with water.  The instructions would be on the back of the bag of concrete as to the ratio of water to concrete.  It is important that you get the ratio correct.  If not, you could get concrete that becomes weaker as it cures.

A weak concrete can lead to crumbling or cracks within a few years.  Although this is the cheapest way to make concrete, when doing it one or two bags at a time, can limit the ability to get results that are consistent.

What Type of Material Reduces the Cost of Concrete?

To reduce the cost of concrete, you can use a new flooring called Bubble Deck.  It is a flat hollow slab that goes in two directions.  Plastic balls are incorporated to replace and eliminate the concrete in the middle of the 20×20 barndominium slab.  Doing this does not contribute to the performance of the structure.

What Type of Material Reduces the Cost of Concrete

Because there is no beam support needed, it can give you longer spans between the supports.  The usage of concrete is reduced significantly.  It is environmentally friendly.  Approximately one kg of recycled plastic will replace 100kg of concrete.

What are Some Other Things That you can add to the Cost?

Some of the things that could add to the cost of your 20×20 concrete slab can include:

  • On average, the concrete slabs are either four or six inches thick and if you add in reinforced wire mesh, that can add $0.30 to $0.80 more per square inch. This includes installation and material.
  • If you decide that you want colored concrete, you can figure another $0.75 to $1.25 per square foot.
  • Sub-base preparation adds $0.60 to $1,25 per square foot. This just includes site-work preparation, which includes compacting the top-grade, grading, ¾ crush stone, installing wire mesh, and wood forms that are 2”x4” or 2” x 6”.


When reading this article, you can see how much concrete you need for a 20×20 barndominium slab is needed and how to calculate the price plus how to make it cheaper.  So, how much does a 20×20 concrete slab cost?It would be, on average, $1,700 to $3.300.

James Hall
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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