30×30 is one of the most common metal building sizes, especially for garages, workshops, storage, outbuildings, and even small warehouses. With 900 square feet of space, these buildings are versatile and useful.
However, you will need a concrete slab.
Concrete slabs provide the foundation or footings for your metal building. However, the thickness of your foundation will depend on where you live, what kind of ground you’re building on, and what you’re using the building for.
On the other hand, you can generally get a good idea of what you’ll pay for a 30 x 30 concrete slab by assessing cost factors and looking at what should impact the total rate.
So, how much should a 30×30 concrete slab cost? Based on national average costs of $5-$9 per square foot, you’re looking at costs of about $4,500 to $8,100. That’s with materials and labor for a slab-on-grade foundation at 4-12 inches thick.
30×30 Concrete Slab Foundations
A 30 x 30 concrete slab foundation or “monolith concrete slab” is the most basic foundation you can opt for. It measures just slightly larger than the building you put on it, and provides a firm and stable base for the building.
This is intended to prevent sinking and shifting of the building. However, it also protects anything you put inside the building. And, if you’re building a barndo or another living space, you’ll need a slab foundation to ensure your home stays warm and dry.
However, even the most basic of concrete slabs are more than meets the eye. For example, you’ll need a graded space under the slab. This means excavating the ground to under the frost line. In some places, this is as much as 4 feet deep. On average, it’s about 10-12 inches.
From there, you’ll have to build trenches to prevent the ground from buckling when it freezes. Then, you’ll decide on the actual thickness of the slab based on the stability of the soil and the weight of the building.
For multi-story buildings, you’ll need an extra thick and reinforced slab. You might also want a thicker slab if the ground is soft. Therefore, actual concrete slab thickness can range from about 6 inches to over 12.
Finally, you’ll build footings in around the foundation to support the foundation and ensure that the graded support under the foundation doesn’t wash away.
How Much Does a 30×30 Concrete Slab Cost?*
The cost of your concrete slab will depend on the dimensions of the concrete slab, the local cost of labor, and the preparatory measures required.
|Reinforcing Mesh / Rebar||$450||$600|
|City Permits / Inspections||$100||$1,300|
|Excavation & Sub-Base||$0||$2,800|
*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.
Slab Cost Calculator For Estimates
Pricing a concrete slab heavily depends on project requirements and location.
These price quotes are just estimates to give you a general idea of different types of costs:
- Basic 4” concrete slab on graded bed – $3,055-$4,722
- 4” concrete slab on 8” sub-base with vapor barrier – $3,434-$6,310
- 6” concrete slab on trenched base with vapor barrier – $5,176-$9,722
- 6” concrete slab on graded bed with vapor barrier and 12” edges – $3,556-$9,552
Of course, if you’re paying union rates for labor, you can typically expect to add about $1,000 in costs to each of those estimates.
10 30×30 Concrete Slab Price Factors
Your concrete slab will vary a great deal in cost depending on factors like the thickness of the concrete, local concrete costs, labor, and truck rental.
In some cases, specific costs won’t apply to you. For example, if you live in a dry area with well-packed dirt, you won’t need much ground preparation. And, if you’re building the form and having your friends help with laying the concrete, you’ll skip a lot of labor costs.
Therefore, it’s a good idea to check which costs actually apply to you and go from there.
1. Slab Thickness
A monolith concrete slab can range from 3 to 12 inches thick. In most cases, about 4-6 inches will do for your project.
If you’re not using the shed for anything but light storage, you can go down to as little as 4 inches thick. However, if you’re using your metal building for tubs, machinery, vehicles, housing, or large animals, you’ll want at least 6 inches thick.
In most cases, you’ll only want to go thicker than 6 inches if you specifically live in an area with soft ground.
Then, if you can’t correct stability by excavating the sub base and replacing it with a firmer soil, you can increase the thickness of the concrete slab to make up for it.
That will be an important factor in costs because increasing the thickness of a slab from 4 to 6 inches increases the concrete used for a 30×30 slab from 11.11 cubic yards to 16.6 cubic yards.
2. Concrete Costs
Concrete typically costs between $104 and $164 per cubic yard if you’re using 3,000 PSI concrete. That’s the minimum strength for most foundation projects.
If you’re going to use the building for very heavy equipment, such as for storing a thresher, you might actually want to go up to 5,000 PSI. That will double the costs.
However, on average, 3,000 PSI concrete is more than good enough. This means you can easily calculate the actual costs of concrete based on the cubic yardage of the foundation.
On the other hand, other costs are almost always location dependent. You’ll have to look at what local companies charge before you can get a precise rate.
3. Labor Costs
In most cases, pouring a concrete slab means several stages of labor. This includes:
- Site Prep and Excavation – Plan to have 2-3 laborers on site for 4-12 hours at $25-$110 per hour, per person.
- Forms – A good crew of 2-3 people should take about an hour to place forms but up to 3 hours if forms have to be deep.
- Pouring the Foundation – You’ll need 3-4 people for 4-8 hours to lay and smooth the foundation.
- Finishing – If you want a smoothed and finished foundation, you’ll have to calculate in extra labor. The smoother you want the concrete, the more time this will take. However, it’s unnecessary for most build projects.
If you calculate in every step, you’re looking at a minimum of 2 days and a maximum of 4 days to lay the foundation. That’s normally a full day or half-day of work per person on the job, which usually works out to $400-$2,600 per person on the job.
For a standard crew of 3, you’ll expect $1,200-$7,800 in labor.
Why do rates vary so much?
In many areas, you can hire concrete laborers at low rates. In others, unions mean you’ll have to pay higher rates. However, on average, you can expect $25-$40 per hour across the United States.
4. Site Preparation
Site preparation can be a significant factor in pricing a concrete slab. However, it might not be.
The height of the water table, existing drainage, soil density, and soil stability will all play a factor. Best-case scenario, you can simply grade the sub-base and be finished.
Worst-case scenario, you may have to excavate, dig trenches, and even replace the underlying ground. That typically costs up to about $5 per square foot, or up to $4,500. However, best-case scenario, you’ll pay $50-$1,800 for the job.
If you need a sub-base, you’ll have to pay for gravel or another material as well as excavation. This typically costs between $10 and $20 per cubic yard. So, if you have an 8-inch-thick sub-base, you’ll pay $169-$338 in sub-base materials.
Of course, installing a sub-base also means adding on more labor, but it will be at the same rate as site preparation.
Having a subbase is also almost always a good idea unless your region is not prone to flooding or you have very firm ground. However, you can always talk to your builder and check local city regulations to see if you need it.
6. Footings and Edges
Footings and edges are concrete or gravel structures around the edge of the concrete foundation, which are primarily intended to act as water barriers. These can protect your foundation from cracking by preventing water from washing dirt out from under the foundation.
Often, they are about 12 inches deep and about 8-10 inches wide. Here, you can expect costs to average $1.50-$24 per linear foot, or $180-$2,880.
In most cases, if the original concrete company also installs the footings, costs will average about $5 per linear foot.
7. Reinforcement Options
Most reinforcement options cost between $0.50 and $2.25 per square foot. This includes reinforcement options like mesh, reinforced mesh, and rebar.
In most cases, you’ll want a mix of rebar and mesh for optimum strength. Therefore, you can expect an average cost of about $1 per square foot or an average of $900. However, costs can go as low as $450 especially if you opt for just mesh.
In addition, if you have a light use shed, you might not want that much reinforcement. Therefore, you could save these costs entirely.
However, mesh will always work to prevent your concrete slab from cracking or buckling, which protects your investment over the longer term.
8. Travel and Delivery Costs
Most concrete companies charge delivery costs, typically per mile they have to drive. Therefore, the further you live from the supplier, the more you’ll pay in total delivery costs.
For example, you can typically expect the truck and delivery to cost from about $600. On the other hand, that could drop to as little as $100 if you’re in off-season and live nearby. Therefore, you’ll always have to check the supplier and their delivery rates.
9. City Permits
If you live within a city jurisdiction, you’ll have to apply for and then pay to install a slab.
Normally, that means from about $100 in building costs. Many cities also charge per square foot – although that can range from about $0.50 to over $10 per square foot depending on where you live.
In addition, you’ll wrap these costs into the full build project for the building you want to install.
10. Optional Extras
There are plenty of optional extras that can add to the cost of a concrete slab. For example:
- Increased Strength Concrete – A 5,000 PSI concrete can cost 30-50% more per cubic yard than 3,000 PSI.
- Vapor Barriers – Vapor barriers cost from about $0.50 per cubic foot but act as a protective measure to keep water out of your structure.
- Finishing – You can polish and smooth the concrete after it cures, making it more suitable for use as an actual floor. This can cost from about $2 per square foot.
We Supply Slabs To All States!
Get in touch with our team for support in pricing and planning your 30×30 concrete slab.
We have locations and contractors in all 50 states, and we’re here to help you ensure your new concrete slab goes as smoothly as possible.
If you’re ready to get started with your concrete slab project, contact us for more information. Or, request a quote to get direct pricing based on your location, ground, and project needs.
We’re happy to help.