If you’re building a two-car garage or a granny flat, you will most likely need a concrete slab. You can use a 15×30 or 450 square foot concrete slab as the garage’s or granny flat’s flooring. The concrete slab will help you keep your structure safe from ground moisture that might result in water damage.
The next question is, how much will such a concrete slab cost you? The price to make a concrete slab depends on its thickness and size. Inflation also plays a role in these computations since the price of gravel, sand, cement, and fill can make your concrete slab more expensive.
This article will help you understand how to estimate the cost of a 15×30 concrete slab to be more precise while preparing a budget.
Table of Contents
What Factors Determine the Cost of a 15×30 Concrete Slab?
Several factors affect the cost of a concrete slab, with size being the primary factor. A 15×30 concrete slab results in an area of 450 square feet, so expect it to be pricier than a concrete slab measuring 12×20 feet since it will use more materials and take longer to make.
Another factor is your location. Building materials can be more expensive in some areas compared to others. In addition, if your location is not easy to access, having ready-mixed concrete delivered can cost more. Some suppliers also add fuel surcharges if the site is beyond their service area.
How Much Does a 15×30 Concrete Slab Cost?
Let’s take a look at some sample cost estimates of a 15×30 concrete slab, depending on different factors.
Per Thickness
How thick your concrete slab should depend on what you use it for. If you are using a concrete slab for flooring, it should be around six inches thick. A thick concrete slab floor is also crucial if your garage houses heavy vehicles like utility vehicles or an RV. A four-inch thick concrete slab foundation should suffice if you plan on building a grilling station outside your barndominium.
| Thickness | Cost per square foot |
| 4 inches | $5.35 |
| 5 inches | $5.80 |
| 6 inches | $6.20 |
| 8 inches | $7 |
Inclusions
Making a concrete slab also comes with incidental costs. Let’s say you have an old concrete slab and want to replace it with a new one. You’ll need to have the old one chipped before pouring in the replacement. If you’re making a concrete slab for your driveway, you’ll want it to be able to hold a great deal of weight, so you’ll need mesh wire and steel rebars to add strength.
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| Inclusion | Cost |
| Site preparation | $1-$2 per square foot (2) |
| Concrete Rebar | $1.40 – $1.85 per 2 feet (3) |
| Wire Mesh | $0.28 per square foot (4) |
With Additional Features
Not all concrete slabs are the same, as some have features you won’t see on others. For example, some pole barn homes have stained concrete floors and stained concrete slab flooring, which cost extra. There are also stamped concrete slabs for driveways or patios that are made to resemble brick, natural stone, wood, or tile. Stamped concrete is an excellent choice if you want to reduce your barndominium’s cost since it is cheaper than tile or brick flooring.
| Features | Cost |
| Vapor barrier | $0.50-$0.70 per square foot (5) |
| Stamped concrete | $9 – $20 per square foot, inclusive of materials (6) |
| Stained concrete | $2 – $4 per square foot, staining only (7) |
15×30 Concrete Slab Cost Breakdown
Let’s look at the individual costs of the different components of a 450-square-foot concrete slab.
Concrete Bag Cost Estimate
This is a vital component of any concrete slab, and a bag of pre-mixed concrete can set you back between $4.50 and $27 each (8). The price difference will depend on the mixture and the concrete bag’s size.
Labor Cost Estimate
If you are hiring a contractor to pour concrete, expect to pay between $2 and $3 per square foot (9). The rates will vary depending on your location since some areas have higher labor
rates. You should also expect to pay more for an experienced contractor compared to a new one in the business.
Truck Cost Estimate
If you want to reduce your labor expenses, order wet concrete and handle the installation yourself. This can also help you save time since you don’t have to mix the concrete you will use. The average cost of concrete delivery is $125 to $133 per cubic yard (10). These rates include the cost of concrete and delivery charges. However, if the site is beyond your supplier’s service area, you might need to pay fuel surcharges of around $20 and $40 per load (8).
How Do You Calculate the Cost of a 15×30 Concrete Slab?
The big question is how much it will cost to pour a 15×30 or 450 square-foot concrete slab. We will give you different price cost averages for a price range to work with as you prepare your budget.
This calculator estimates that a 6-inch thick 15×30 concrete slab will use 8.333 cubic yards of concrete. We are also adding 10% to the size to account for waste allowance. This means you should prepare 9.17 cubic yards of concrete.
The National Ready Mixed Concrete Association states that the average cost of concrete is $137 per cubic yard for 2022 (11), so the cost of concrete for a 450-square-foot concrete slab should be around $1,256. When you add the cost of labor at around $2-$3 per square foot (9), your 15×30 concrete slab should cost between $2,156 and $2,606.
Another way is to calculate the cost of your concrete slab per square foot. A 15×30 concrete slab has an area of 450 square feet. As mentioned earlier, a concrete slab that’s six inches thick costs around $6.20 per square foot, inclusive of labor (1). This means that your 450 square feet concrete slab should cost around $3,069, inclusive of the 10% waste allowance.
Should You DIY or Hire a Contractor for Your 15×30 Concrete Slab Project?
We believe it would be best if you hire a contractor to make your 15×30 concrete slab. While you can save money by doing a DIY concrete slab, a professional can complete the job faster and better. A professional can also help ensure that your concrete slab is properly done to serve its purpose, whether it’s as a driveway, patio floor, walkway, or granny flat floor.
Conclusion
Concrete slabs are crucial to the success of almost any building project. A concrete slab can function as a floor, a foundation for a grilling station, or a driveway. Whether you’re building a barndominium, a shouse, or a garage, you will most likely require a concrete slab, so knowing how much it costs to build one is crucial.
Accurately identifying the cost of a concrete slab can also help you project the cost of financing a barndominium if your floor plan calls for a concrete slab floor. Using our guide, you can come up with a reliable computation and adequately prepare your budget, so there will be no surprises when it’s time to build your 15×30 concrete slab. Like and follow our Facebook page for more useful building tips and articles.
- How Much Does A Concrete Slab Cost In 2023? Homeadvisor.
- Cost Of A Concrete Driveway ConcreteNetwork
- What Are Common Rebar Prices for Concrete Projects? Angi
- How to Compare the In-Place Cost of Wire Mesh Versus Synthetic Fibers ABC Polymer Industries
- How Much Does Crawl Space Encapsulation Cost? Angi
- Stamped Concrete Cost For Patios, Driveways & More ConcreteNetwork
- Concrete Floor Cost – What You’ll Pay For Polished Or Stained Concrete ConcreteNetwork
- How Much Does Concrete Cost? Angi
- How Much Does a New Concrete Slab Cost? Angi
- How Much Does It Cost to Have Concrete Delivered in Your Area? Fixr
- Ready Mixed Concrete Industry Data Survey. NRMCA
