How Much Does a 20×30 Concrete Slab Cost?

When building your barndominium, one of the most important components is the concrete slab.  Barndominiums use a concrete slab instead of a traditional foundation as the base for the building. This aspect of the build is crucial and getting it right determines the strength and safety of your home. Because of this, it’s a good idea to know how much you can expect to spend on a quality slab. 

The average cost of a 20×30 concrete slab is between $2,400 and $4,800. However, there are quite a few factors that may change this price.

Understanding these factors can help you price your 20×30 concrete slab and be ready for construction. In this article, we have laid out everything you need to know about laying a 20×30 concrete slab. 

20x30 concrete slab

What is a Concrete Slab? 

A concrete slab acts as the base for buildings like shops, barndominiums, and even traditional homes. They are the solid, flat surface that the rest of the home is built on and they need to be correct. The craftsmanship of the 20×30 concrete slab will determine the quality of the rest of the home. Because of this, you do not want to cut corners with this specific part of your build. 

With barndominiums, the plumbing is set inside the concrete slab. The posts that hold up the walls and roof are also sunk into the slab.

Because of this, it is crucial that the slab is correctly installed and has the right thickness. Understanding the costs associated with this will help you make the right choice. 

What Does a 20×30 Concrete Slab Installation Include? 

When installing a 20×30 concrete slab, you are getting more than just the installation. You are also getting all the checks and extra features you need to ensure a quality job. This includes things like 3,000 PSI concrete poured to a six-inch thickness and the fiber mesh reinforcement. You also get the rebar to support the slab itself, which is essential for structural integrity. 

One of the most important things that come with 20×30 concrete slab installation is labor. Pouring a slab is a very involved process and requires a lot of manpower. By making sure that you get all the help you need, you can ensure a quality final product. This help and expertise make the cost well worth it in the long run.  

20x30 concrete slab

Factors That Determine the Cost of a 20×30 Concrete Slab 


The thickness of your concrete slab is important and will determine the durability of your home. Most concrete slabs need to be around six inches thick but this can also vary. Depending on where you live and what the building codes are like in your area, you may want more. If your barndominium is going to be very small, you can usually have a thinner slab.

The thickness of the 20×30 concrete slab will also change depending on your plumbing. Because the plumbing in a barndominium is set in the slab, it can change your thickness requirements. If you have a lot of lines and pipes, you may want to increase your thickness. Speak with your builder to decide what size you will need. 

The average prices of concrete slabs by thickness include: 

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

Labor Costs 

The cost of labor will also determine the cost of your 20×30 concrete slab. Depending on where you live and what the labor market is like, you may end up paying more. The best way to find out is to get quotes from a wide variety of contractors. This will help you narrow down your choices and give you a lot of quotes to choose from.

You do not want to cut costs in terms of labor when installing a 20×30 concrete slab. Having professional craftspeople on your side is essential with a project like this. The slab needs to be level and completely cured before anything can be built on it. Labor can be expensive, but having the benefit of professionals at your disposal is priceless. 

20x30 concrete slab

Extra Features 

Your concrete slab can also come with extra features that will make construction much easier. These extra features include thickened edges, wire mesh reinforcement, and a vapor barrier for the flooring. If you are looking to have the strongest, most structurally-sound slab, these are great options. You may also need to install them to be in compliance with your local building codes.

Getting the extra features may cost more but they can be well worth it. For example, you will need a vapor barrier to install flooring like tile or laminate in your barndominium. Making sure that you get the best extra features will end up saving you money in the long run.

Speak with your contractor to find out what features are available to you. 

DIY vs. Professional Installation 

When thinking about installing a 20×30 concrete slab, you might be considering a DIY installation. A concrete slab is a relatively simple job but it does require a lot of expertise. If you are completely unfamiliar with the process, you may want to have a professional handle it. 

This is especially true with a barndominium concrete slab installation. Because the posts are sunk into the slab, you will need your slab installer to work with your general contractor. This kind of coordination and professionalism can make the extra cost well worth it. 


If you need to install a 20×30 concrete slab, it is important to know what that entails. Knowing all the different factors that can determine the cost will help you be ready. A large project like this requires you to prepare for the costs and expect the best. This is especially true with such a structurally important component of the build. 

If you would like more helpful advice from the pros, be sure to check out the rest of There, you will find information on financing and insurance, our recommended software to design your own plan, and other tips and tricks. You will also find featured barndominiums to help get you inspired for your own custom home.