A concrete slab is the foundation for your building, providing the support and stability for your metal building. 30 x 50 is a standard size for garages, workshops, storage, and even small warehouses. And, with 1,500 square feet of space, you can do a lot in 30×50.
A simple slab-on-grade concrete foundation is the most common base for these buildings. That’s because it’s cheap, relatively quick to install, and provides the support needed for even heavy machinery. However, you’ll have to adjust your foundation thickness and type to the location and weight of the building.
A 1,500 square foot building requires minimal support in most cases, which means you can likely get away with a 4-6″ foundation with small concrete piers under each of the building supports. That will cost you roughly $5-$9 per square foot – or $7,500-$13,500. However, actual costs will depend on prep work, local cost of labor, the condition of the soil, and other factors.
What Are 30×50 Concrete Slab Foundations?
A 30×50 concrete slab (usually 30’2” x 50’ 2”) is the perfect base for a metal building for almost any purpose. For example, 30×50 is one of the most common sizes for barndominiums. Here, you can get a single or a two-story home on a simple concrete slab for a minimum of expense and build-time.
30×50 buildings are also ideal for:
- Modular homes
- Warehouses
- Garages
- Workshops
- Small retail shops
- Storage and Warehousing
- Agricultural Buildings
However, depending on the weight of your total build, you’ll have to take different things into account. For example, if you have a heavy building or are storing agricultural equipment, you’ll have to prepare the foundation. That normally means using a trenched sub-layer under the foundation to ensure proper support.
Most builders will also recommend using concrete piles under the primary support posts for your building, although this won’t increase total costs too much.
30×50 Concrete Slab Cost Breakdown
The costs of your concrete slab will depend on several factors such as area, local cost of labor, cost of rental, and what type of foundation supports you need. The following chart outlines the most expected cost ranges for a 4-6′ thick foundation.
| Costs | Cost per Sq. Ft. | Low | High |
|---|---|---|---|
| Concrete | $2.44-$3.60 | $3,666 | $5,466 |
| Concrete Truck | NA | $600 | $1,400 |
| Reinforcing Mesh/Rebar | $0.50-$1.20 | $735 | $1,830 |
| City Permits/Inspections | NA | $100 | $1,300 |
| Forms | $0.06-$0.80 | $90 | $1,200 |
| Excavation & Sub Base | $0.05-$1.50 | $75 | $2,250 |
| Labor | $2-$3 | $3,000 | $4,500 |
| Vapor Barrier | $0.05-$0.20 | $75 | $300 |
| Total | $5.17-$12.13 | $7,756 | $18,196 |
*Please note these costs were based on quotes at the time of writing in July 2023 and may be different at the time of reading. Actual costs are subject to location, time of year, and market. Please use these numbers as a basis for your own research.
It’s also important to keep in mind that some things are optional. For example, you may not need the vapor barrier or city permits. However, you’ll likely always need reinforcing mesh and rebar.
8 30×50 Concrete Slab Pricing Factors
There are a lot of factors that go into the actual cost of a concrete slab. For example, the local cost of labor is a large consideration. Your location and access to concrete will also impact the price you pay per cubic yard. Therefore, you’ll have to review local data before you can accurately quote your slab.
1. Slab Thickness
Most 30×50 buildings can use a simple 4-6″ concrete slab, depending on weight and ground composition. Here, you may have to do a soil test before building. However, on average, you can expect that a 4” slab is good enough for storage and warehousing usage unless you need a forklift. However, you’ll need a 6” slab for residential usage and will probably want one for offices, retail stores, and agricultural areas.
This means that on average, you will want a 6” slab. This means you can expect to use 33.33 cubic yards of concrete. Concrete typically costs $104-$164 per cubic yard for 3,000 PSI concrete. In most cases, that’s all you’ll need. However, it also means that if you can get away with a 4” thick slab, dropping concrete usage down to 22.22 cubic yards, you could save, on average, over $1,000 in materials costs.
If you’re not sure, talk with your metal building provider to see what they recommend for your installation.
2. Slab Reinforcements and Subbase
In some areas, you can simply grade a 1,500 square foot plot and pour concrete on it. In others, you’ll have to prepare the sub-base. Depending on the weight of the building, you’ll also want to prepare the lot. For example:
- Excavation to place the foundation at ground level
- Excavation to add trenches for increased foundation stability and drainage
- Concrete piles under the primary building supports (If you have a 2-story building, you need this)
- Gravel or other drainage layer between the foundation slab and the dirt underneath
Again, if you’re not sure, you should consult with a professional who can offer guidance on what you need in terms of stability and strengthening measures. However, piles cost about the same as the concrete slab in terms of cost per square foot. In addition, you can expect to pay about $10 and $20 per cubic yard for sub-base materials. This means you’ll pay from about $95 for a sub-base but up to about $700 depending on the total thickness of the sub-base.
What you need also heavily depends on your location and the composition of the ground. The dryer and harder the ground, the less prep you’ll need.
3. Grading and Excavation
Best-case scenario, your foundation can be set on a simple graded bit of ground. This “Slab-on-grade” foundation is the most popular option for commercial buildings in the United States. However, you may also have to excavate. That’s especially true if you have to install a sub-base, want water drainage, want a sewer installation, etc.
Excavation costs won’t always be a factor. However, if they are, you can estimate that costs go up to about $5 per square foot. That can mean you pay up to $7,000 in site preparation. Best-case scenario, you’ll pay closer to $90. Therefore, you’ll want to have a site inspection and figure out what you need before costing your slab preparation.
4. Local Cost of Labor
Labor costs can range from as low as $10 per hour to over $100 per hour. For example, in New York you can expect to pay $90 or more per hour for most laborers. In rural parts of the United States, rates of $10-$15 per hour are more common.
- Union areas typically charge from $75+ per hour
- The national average laborer day rate is $300
Typically, you’ll need a 3-10 man crew for a concrete slab. That can mean paying over $1,000 per day in labor. For multi-day jobs, you’ll spend several thousand per day.
Labor also includes more than just pouring the concrete. For example:
- Site prep
- Laying forms
- Pouring the concrete
- Curing and potentially finishing the concrete
In addition, if you’re using the concrete floor as-is, you may want to finish it afterwards. That can mean smoothing and polishing or even adding a finish layer to the top, which can cost thousands of dollars. However, it’s also likely cheaper than installing new flooring material.
5. City Permits & Inspections
If you’re building inside city limits, you’ll have to pay for a planning permit. Depending on location, that can be anywhere from about $90 to over $1,500. For example, the city of Chicago charges by the square foot, meaning that a permit for a 1,500 square foot building could be over $4,000. On the other hand, most areas charge a flat rate, so you’ll have predictable costs.
In addition, even if your location charges by the square foot, most charge a reduced rate for non-heated spaces. This means you can expect to pay about 10 to 30 cents per square foot for agricultural and warehousing buildings.
On a national average, building in city limits will cost about $100-$750 but up to about $7,000. Outside of city limits, you won’t pay for a permit.
6. Reinforcement and Concrete Strength
Most metal buildings require a reinforced concrete slab, which means using either mesh or rebar (or both) to stabilize the concrete and prevent it from cracking. However, these materials are typically very cheap, so you do want them.
In fact, you can typically get reinforcing mesh from about 0.50 cents per square foot. You can also get rebar for between $1 and $2.25 per square foot. However, you will want to talk to your builder to determine what you need and what is standard for a 30×50 foundation in your area.
Why? Foundation reinforcement needs are determined by ground stability, likelihood of flooding, and likelihood of earthquakes. Some regions are very stable and others are not. So, the strength requirements of your slab can vary quite a bit depending on where you’re building.
7. Actual Cost of Materials
Material costs can also go up and down quite a bit. For example, the cost of concrete can range from $104 to $160+ per cubic yard. That’s a big price difference. Rebar costs can also more than double depending on where you’re at.
In some cases, actual costs are about accessibility. Building in an industrial build area where there’s already a large supply of concrete will be a lot cheaper than attempting to source concrete in the middle of nowhere where you’ll have to import Portland cement to mix your concrete. Therefore, it’s important to take your location into account when calculating material costs. National averages mean very little on a local scale.
8. Optional Extras
You can almost always increase the cost of your concrete slab by adding extras. For example:
- Site Inspections and Soil Testing – $800-$1,500+
- Vapor Barriers – $0.05 cents per square foot
- Finishing – From $2 per square foot
- 5,000 PSI concrete – If you want more floors, you’ll need stronger concrete
- Edges – $1-$5 per linear foot
In each case, you should discuss your needs with your builder to determine what’s nice to have, what’s necessary, and what’s a waste of money.
Cost Calculation Examples
Pricing a concrete slab heavily depends on what you want. Your location and travel distance will also play a role. However, you can see a few different estimates below.
- 4” slab on grade 30 x 50 – $7,500
- 4” slab on grade in city area – $11,149
- 6” slab on grade with vapor barrier and trenched base – $15,225
- 6” slab on gravel bed – $8,800
The best way to do this cost estimate for yourself is to determine what you need so you can cost out each part of the slab locally. You might also want to price the cost of a 4” vs a 6” slab separately, just to see how much the actual cost increase is. However, you’re building a barndominium, you need the 6” slab to meet code requirements.
Our Coverage
Talk to our team to discuss your 30×50 concrete slab needs. We’re always available to help you ensure your land prep and concrete pour go as smoothly as possible, so you’re ready for building erection. Rex Metal Buildings covers the full continental United States and we’re happy to offer a quote for a concrete slab, to your specifications.
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Use the contact form to get in touch and request a quote for your 30×50 concrete slab, customized to your location. We offer concrete pouring services in all 50 states and we’re happy to get you in touch with one of our contractors in your area.