How much does a 30' x 30' concrete slab cost in 2023

I'm going to share with you what it will cost to have a 30' x 30' concrete slab installed in 2023.

My name is Mike Day. I've owned Day's Concrete Floors, Inc since 1985. My company installs many concrete slabs every year of various sizes.

These 4 sizes are pretty popular and I think it's important for people to know what they cost.

Disclaimer: Keep in mind, these are my prices for installing concrete slabs for my customers in Maine. Prices could vary significantly depending on where you live and who you hire.

how much does a 30' x 30' concrete slab costThis is a basic 30'x 30' garage slab

What is the basic cost for a 30' x 30' concrete slab

The estimated cost for a 30' x 30' x  6" thick concrete slab is $8.50 per sq. ft. or $7650.00.

I get $7650 by figuring out the square footage, 30 x 30 = 900 sq. ft.

Then, I multiply the square footage, 900 by the cost per square foot, $8.50 and that = $7650.00



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What's included in the updated slab price for 2023?

The materials included in the above slab price are:

  • 18 yards of 3000 psi concrete mix @ 150.00 per yard
  • Wire mesh reinforcement
  • A double row of #4 rebar around the edges
  • Labor to form the slab
  • Labor to place the concrete and apply a smooth trowel finish
  • Labor to saw contraction joints (to help control cracking)
  • Install anchor bolts (if you want them)

What's not included in my 30 x 30 slab prices

I only specialize in doing the concrete work. I don't do the excavation and gravel work. So preparing the sub-base for the concrete slab is not included in my prices.

The sub-base for a concrete slab is very important and should consist of 3/4" crushed gravel, road base, or compacted sand.

The thickness of the sub-base will vary depending on where you live. In Maine, where we get a lot of freeze and thaw weather in the winter, the minimum sub-base thickness I like is 24 inches.

If you don't get any freezing weather, then 6 inches of gravel will work good for most cases. 

Excavation and preparation for the gravel sub-base will be based on your local conditions and it would be best to get a local contractor to assess your specific needs.

The price to excavate, gravel, and prep the sub-base in the slab pictured above was $4500.00

Can I just have a 4" thick slab instead of 6"

Sure you can. In Maine, most of the building codes require us to install 6" thick concrete slabs. If you're codes are different, a 4" thick slab with a good compacted gravel base will be strong enough for most residential garages. 

The only difference in price would be the 2" of concrete which comes to 5.5 yards for a 30' x 30' slab. So you could deduct $750 dollars from $4950.00.

A 4" thick 30x30 slab would cost $4200.00

What are some other things that would add to the cost?

THICKENED EDGES: Some towns and cities building codes require a thicker edge when installing concrete slabs. They could be 12" thick, 16" or even 18" thick. We call these haunched slabs.

The edge of the slab is 12" deep or more by 12 - 24" wide, then taper up to 6" thick for the rest of the slab. 

ADDED COST FOR THIS: $1.00 - $2.00 PER SQ. FT.

2" STYROFOAM UNDER THE SLAB: Our building codes require 2" Styrofoam under concrete slabs of 600 sq. ft. and larger. The Styrofoam helps insulate the slab from the cold sub-grade, helps keep the slab from heaving and cracking in cold climate areas, and is used if radiant heat is being installed in the slab.

ADDED COST FOR 2" STYROFOAM: $2.50 - $3.00 PER SQ. FT.  (includes installation of the Styrofoam also)

Thicker edges and Styrofoam are the 2 things we have to deal with the most here in Maine. You may not have to consider these where you live but I thought I would include them for those who do. 


What is the cost of a 30' x 40' concrete slab?

Based on the information I gave you above:

30' x 40' = 1200 sq. ft.

1200 sq. ft. x $8.50 = $10,200.00



What is the cost of a 20' x 30' concrete slab?

Based on the information I gave you above:

20' x 30' = 600 sq. ft.

600 sq. ft. x $8.50 = $5100.00



What is the cost of a 24' x 24' concrete slab?

Base on the information I gave you above:

24' x 24' = 576 sq. ft.

576 sq. ft. x $8.50 = $4896.00


Remember, the above prices are for 6" thick concrete slabs. If you only need a 4" thick slab the prices would be a little less because they require less concrete.

How much does a 40' x 60' concrete slab cost?


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