Ever wanted to build a shed but don’t know where to start? Afraid the cost will be to the moon? The best place to start is a concrete slab for a base. It will support almost anything and also makes a great floor. Once you have the concrete base, you can build a shed, assemble a shed, or have a ready-made placed on it. But how much does a concrete slab for a shed cost?
A concrete slab for a shed will cost between $4.00 and $5.00 a square foot assuming you do all the preparation work. If you hire someone to do the job for you, the price can be double, or higher. Just multiply the length and width of your proposed shed by $4 or $5.
In this article, we’ll take a look at what is needed to build a concrete slab for a 12’x14’ shed and how much it will cost.
Typical Thickness of a Concrete Slab for a Shed
The thickness of concrete depends upon what you plan to store in your shed, and also the soil, and the climate you live in. A 2-inch thick concrete pad in Florida won’t survive the freeze-thaw of winter in Idaho or New York. Sand vs. loam vs. clay are other considerations too.
The typical thickness for a concrete slab is 4-inches. It will support a motorcycle, quad, boat lawn and garden tractors, cars, and even a 9000-pound forklift.
For heavy equipment such as bulldozers and skidders, a 6-inch pad is recommended. The physical size of your shed also determines what will fit in it.
The difference between a concrete slab and a slab-on-grade is the thickness of the perimeter. A slab is the same thickness throughout. A slab-on-grade has an 8-inch thick (or thicker) reinforced perimeter that acts as a foundation to support the walls and the edges of the slab.
The first thing you need to decide is the size of the shed you want, so you know the size of the concrete pad you need. Once you determine the size, you need to figure out where to put it in your yard.
A concrete slab works best on flat ground or ground with a slight slope. Remember to check for underground utilities and get a building permit if necessary.
After determining the size and location of your shed, you need to clear the area and remove the top 4” of soil. I won’t include the cost of preparing the site or permits since they will be different for everyone.
Now you’re ready to put down 4-inches of ¾” crushed stone for drainage; spread it and tamp it down. With the gravel in place, you need to build the 2”x6” forms, which will give you a 4-inch thick concrete pad.
The optional rigid insulation would go on top of the gravel, then the moisture barrier. The rebar grid would be placed next, followed by the concrete.
Suggested reading: for more information on building a concrete slab, read How to Pour a Concrete Slab Foundation for a Shed.
What Type of Concrete Should You Use?
The typical concrete is rated at 4000psi. It will support anything you normally can put into a shed – even that 9000-pound forklift! However, for an extra cost, you can get higher strength concrete with ratings of 5000psi and 6000psi.
There is also a crack resistant concrete, which has a synthetic fiber blended in to help prevent cracking; it also doesn’t require steel reinforcing in supported slabs.
What are the Components of a Shed Concrete Slab Price
There are too many permutations of length and width for a concrete pad for a shed to calculate all slab prices. I’ll use a 12’x14’ shed slab as an example and list the components with unit prices – prices change daily and seasonally on many of the materials, so check your local suppliers for current prices.
The average cost of a do-it-yourself concrete pad is between $4.00 and $5.00 a square foot.
The cost to install a cement slab includes the following materials and assumes you do all the prep work yourself. If you hire someone to do it for you, the labor cost usually doubles (or more) the price of doing the work yourself. Additionally, if you live in an area where gravel and concrete are less expensive, then the cost will be less.
Gravel subbase: the cost of gravel per cubic yard is $115.00 + delivery (price often goes down when ordering more). I use 4-inches of crushed stone gravel (21-A grade). The 12’x14’ pad would need 2.05 cubic yards and cost $238.56. (115÷27÷3=$1.42/sqft)
The best material for under the concrete pad is ¾” gravel with smaller particles and dust to compact. Its cost per cubic yard varies. I picked a cost closer to the upper end; check out your local supplier or this link.
Concrete forms: 2”x4”x8’=$3.15, 2”x6”x8’=$5.46, 2”x6”x12’=$8.90, 2”x8”x12’=$16.57
The 52-foot perimeter of the pad needs 2”x6” perimeter forms with 2”x4” bracing every 2 feet and would cost $56.16 based on linear foot measure. ($1.08 a linear foot)
Moisture Barrier: the cost of 6 mil moisture barrier is $34.83 for 20’x50’ roll – you won’t need the whole role, and may be able to get a smaller piece based on your shed size. ($34.83/1000sqft=$0.034/sqft)
Reinforcement: rebar is sold by the foot, but the more you buy, the lower the price. I’d use ½” rebar to make a 2’x2’ grid. A 12’x14’ concrete pad would require 194-feet of rebar at $0.79/foot for a cost of $153.26. ($0.79 a linear foot)
Concrete: the cost of concrete per cubic yard is $119.54 + delivery (price often goes down when ordering more). For a 4-inch thick pour in the 12’x14’ base 2.05 cubic yards which would cost $248.64. (119.54÷27÷3=$1.48/sqft) You may want to round down to 2 cubic yards, or round up to 2½ cubic yards; each will affect the cost.
The cost of concrete varies greatly, so I picked the average between the highest and the lowest that I found. For a more accurate calculation, contact your local supplier or check out this link.
Note: Concrete is usually delivered in ½ or full cubic yards. You may want to have something else formed up to take the extra concrete.
Insulation: the cost of 2” R-10 rigid insulation also varies, but the price I have is $33.92 for a 4’x8’ sheet. That work out to $1.06/sqft, so $178.08 to insulate under the 12’x14’ pad.
In the table below, we’ve attempted to provide an accurate material cost for a concrete slab for a shed. Prices will vary depending on your location and the distances from suppliers. Labor and delivery are not included.
|4” Thick Concrete Slab||Unit Cost||6X8|
|4” of Gravel (21-A grade)||$1.42/sqft||0.59 yd³|
|2”x6” perimeter forms with 2”x4” bracing every 2 feet||$1.08/foot||28 feet|
|20 mil Moisture Barrier||$0.034/sqft||$1.63||$3.40||$5.71||$8.16|
|½” rebar 2’x2’ grid||$0.79/foot||62 feet|
|4” of concrete|
What Can Make the Cost of Concrete Pad to Go Up?
There are many factors that can make the cost of a concrete pad increase. Local codes may require you to use a slab-on-grade with a 12-inch thick perimeter.
Supply and demand for steel and lumber affect prices too. The distance you are from the gravel pit or cement plant also impact the price.
And finally, how easily the job site can be accessed is another factor, getting materials to the site may increase the cost.