When building a new metal structure—whether it's a barn, workshop, garage, or agricultural building—the foundation is critical. One of the most popular foundation choices for metal structures is a concrete slab. A well-poured concrete slab ensures your metal building has a stable, durable base that can withstand the weight of the structure and protect it from environmental factors like moisture and soil movement. In this blog, we’ll walk through the detailed steps for pouring a concrete slab for your new metal structure. By following these steps, you can ensure that your building will be both strong and long-lasting.

Step 1: Planning and Permitting

Before starting any construction project, it’s crucial to have a clear plan in place, especially for foundational work like pouring a concrete slab. Begin by determining the dimensions of your metal structure. This will guide the size and thickness of the concrete slab you need to pour. The slab should be slightly larger than the footprint of your metal structure to allow for adequate edge support and stability.

Once you've planned the slab dimensions, consult your local building codes. Depending on where you're located, you may need to obtain permits before pouring a concrete slab. Failing to secure the proper permits can result in fines, delays, and the possibility of having to remove the slab altogether. Permits will ensure that the slab is constructed in compliance with safety and environmental standards, especially concerning load-bearing capacities and drainage.

Step 2: Preparing the Site

The next step is preparing the site where the concrete slab will be poured. Site preparation is essential for ensuring the longevity of your concrete foundation. Start by selecting a level piece of land. The area should be free from large rocks, roots, and debris, which could cause unevenness or compromise the integrity of the slab. If necessary, use a backhoe or bulldozer to level the site.

Once the area is cleared, mark the perimeter of your slab with stakes and string. This will serve as a guide for your excavation. Using a measuring tape, ensure that the dimensions are accurate according to your metal structure's foundation plan. The next step is excavation. For most metal structures, you will need to dig to a depth of around 6 to 8 inches for the slab, though this may vary depending on your soil type and climate. In areas with heavy frost, you might need to dig deeper to prevent frost heave, a condition where the ground freezes and expands, which can crack or shift the concrete.

Step 3: Creating a Gravel Base

With the site excavated, it’s time to create a base layer for the concrete. A solid base is essential for drainage and preventing future shifting or cracking of the concrete. The best material for this base is compacted gravel. Begin by laying down a 4- to 6-inch layer of crushed gravel or stone across the entire excavated area.

Spread the gravel evenly using a rake, then compact it with a plate compactor or hand tamper. Compacting the gravel ensures that it settles uniformly, reducing the likelihood of future settling or movement beneath the slab. Once the gravel is compacted, you should have a smooth, level base that will support the concrete.

Step 4: Building the Forms

Next, you’ll need to build the forms that will contain the wet concrete as it is poured. Forms are typically made from sturdy wooden planks, such as 2x4s or 2x6s, which are secured around the perimeter of your slab. These boards are held in place by stakes driven into the ground and fastened to the planks with screws or nails.

The height of the forms should match the thickness of the slab you intend to pour, which for most metal structures is between 4 and 6 inches. It's crucial that the forms are level and square, as any irregularities will show up in the finished slab. Use a spirit level or laser level to ensure the forms are perfectly level across the entire perimeter. Additionally, double-check the angles and dimensions to ensure the forms are square, using a framing square or measuring diagonally across the forms to confirm that the corners form perfect right angles.

Step 5: Reinforcing the Slab

Reinforcing the slab is a key step in ensuring that your concrete foundation will be strong enough to support your metal structure. Most concrete slabs are reinforced with either steel rebar or welded wire mesh, both of which help to increase the tensile strength of the concrete and prevent cracks from forming due to shifting or settling soil.

For rebar reinforcement, lay a grid of rebar throughout the area inside the forms. Typically, the rebar is placed 12 to 18 inches apart in a crisscross pattern, creating a mesh-like structure. Ensure that the rebar is suspended slightly above the ground—this can be done using small concrete blocks or "rebar chairs" to keep it in place during the pour.

Alternatively, you can use welded wire mesh, which is laid directly on top of the gravel base. Like rebar, the wire mesh helps distribute the load across the slab and prevents cracks from developing. The choice between rebar and wire mesh will depend on the size of your slab and the weight of your structure, with rebar typically being the more durable option for larger buildings.

Step 6: Mixing and Pouring the Concrete

Now comes the most critical part: pouring the concrete. First, calculate the volume of concrete needed by multiplying the length, width, and thickness of the slab. Most concrete is ordered by the cubic yard, so ensure you have enough to complete the project in one go, as it's best to pour the entire slab in a continuous pour for uniformity.

You have two options for pouring the concrete: mixing it yourself on-site with a portable mixer or ordering pre-mixed concrete from a local supplier. For larger slabs, it's often more practical to have a concrete truck deliver pre-mixed concrete. This will ensure that the consistency and strength of the mix are uniform.

Start by pouring the concrete into the forms, spreading it evenly across the area. Use a shovel or rake to move the concrete into all corners and edges of the forms. As you pour, periodically tamp the concrete to remove any air pockets, which can weaken the slab over time.

Once the slab is poured, use a straightedge, also known as a screed, to level the surface. Run the screed across the top of the forms to smooth the concrete and ensure it is level. For larger slabs, you may need a partner to help screed the surface evenly.

Step 7: Finishing the Surface

After screeding the concrete, it’s time to finish the surface. This involves smoothing and leveling the top of the slab for a polished, professional look. Begin by using a bull float, a large, flat tool used to smooth the surface of the concrete. Glide the bull float across the slab in long, overlapping strokes to remove any ridges or bumps left from screeding.

Once the surface is floated, allow the concrete to set slightly. You want the concrete to be firm enough to support your weight without leaving deep impressions. At this point, you can use a hand trowel to smooth the surface further. For a textured, non-slip finish, you can also run a broom across the surface to create fine lines that add traction, which is especially useful for outdoor slabs exposed to rain.

Step 8: Curing the Concrete

Properly curing the concrete is essential for achieving maximum strength and durability. Curing involves maintaining the moisture level of the concrete to prevent it from drying too quickly, which can cause cracks and weaken the slab. Once the surface is smooth, cover the slab with plastic sheeting or burlap, and keep it moist by spraying it with water periodically over the next 7 to 10 days.

During the curing process, avoid placing heavy objects on the slab, and minimize foot traffic to prevent any damage or uneven settling. Curing times can vary depending on the temperature and weather conditions, but in general, concrete reaches its full strength after 28 days.

Step 9: Anchoring the Metal Structure

Once the concrete has fully cured, you can begin anchoring your metal structure to the slab. Most metal buildings are anchored using bolts or fasteners that are either set into the wet concrete during the pour or drilled into the slab after it has cured. Be sure to follow the manufacturer's instructions for anchoring your specific structure, as improper anchoring can lead to structural instability.

Anchoring is a crucial step in ensuring that your metal building remains secure and stable, especially in areas prone to high winds or seismic activity. Proper anchoring will also prevent the building from shifting or settling over time.

Final Thoughts

Pouring a concrete slab for your new metal structure is a multi-step process that requires careful planning, precision, and attention to detail. From site preparation and reinforcement to pouring and curing the concrete, each step is critical to ensuring that your foundation is solid, durable, and capable of supporting your building for years to come. With the right preparation and techniques, you can create a slab that will serve as the perfect base for your metal structure, ensuring its long-term stability and functionality.

Metal Buildings Are Smart Solutions

Thinking about going with metal building kits, or a metal building for sale to solve your outdoor storage needs? That’s a good call, especially if you partner with a pro like WZH. Our custom-designed steel structures are fantastic solutions for all sorts of residential, agricultural, commercial, and industrial applications.

Some initial things to decide are exactly where you intend to place the new building on your property, and which type of foundation material you’ll require. With a prefab steel structure, you have plenty of flexibility in terms of foundation options. These versatile buildings can be installed and anchored on concrete, asphalt, gravel, or even plain, level ground. But if your particular building application calls for concrete, you’ll need to add pouring a concrete slab to your metal building foundation planning checklist.

Site Preparation Considerations

Most metal building providers don’t provide groundwork or concrete services themselves, so there are a few things you’ll need to do to get your site ready in advance of your scheduled installation:

• Stake out the footprint of your chosen building width and length on your lot. It’s also a good idea to use a simple line level to check just how level your land is. This isn’t hard to do yourself; there are helpful video tutorials like this that can guide you through the process. If your install site is too far out of level, you’ll then need to take steps to address that.

• Make sure to obtain any applicable building permits that may be required in your local area.

• Ensure that your site is level. In order to avoid any cut leg fees, additional labor fees, or return trip fees related to metal building installation, your site can’t be more than 3” out of level. And if you’ll be using a poured foundation like concrete, it’s really best to begin with a site that’s true level.

• Mark any utility lines that run through or around your building site. If you’re not sure about the exact locations, you can call 811 and ask a local official to come mark your lines for you. This is typically a free service offered to property owners.

• Clear away any trash, debris, or overgrowth from your building install site. Install crews generally need a minimum of 3’ of clearance on all sides in order to have the necessary room to work in putting up your building.

By partnering with WZH, you can ensure that your metal building project is set up for success from the start.

What Should the Poured Pad Measurements Be for a New Metal Building?

That’s an important question, and it’s also one of the more common questions we get about metal building installations at WZH. In most states, your pad will need to match the exact width of the building to be installed and should measure 1’ shorter than the length of your building’s roof. One key exception to that rule is Florida. The state of Florida requires a concrete pad to be ¾” wider than the building, and the pad length needs to exactly match the length of the building. Got more questions about concrete pad measurements for your new metal building? Just give one of our building specialists a call at (980) 819-4368.

Concrete Considerations – To Pour Yourself, or Not?

Before you decide to pour yourself, just be aware that there are potential concerns that go along with any DIY concrete project. Pouring concrete does require a certain amount of knowledge, tools, and skill. Inexperienced homeowners can inadvertently overlook important details. Without the right type and amount of concrete, the right mixing approach, the right tools, and the ability to set the proper forms, many frustrating headaches can occur. If you’re not confident in your ability to work with concrete, it really might be best to leave the task to a professional. WZH regularly installs custom metal buildings in 46 states, so if you’re looking for a reputable concrete contractor, one of our building specialists can probably refer you to someone who serves your local area.

How to Lay a Slab of Concrete

All that being said, if you’ve landed on the design of your new metal building from WZH and are ready to proceed, we’re here to help you make it happen! Make sure to communicate your choice of a foundation surface to your building specialist whenever you place your building order, so we can be sure to include the proper concrete anchors.

A quick internet search can yield a number of different DIY concrete slab tutorials, but the basic steps for how to pour a concrete slab are as follows:

1. Obtain the proper safety equipment. Since concrete is known to be a skin irritant, it’s best to wear long pants, a long-sleeved shirt, rubber boots, waterproof gloves, and safety goggles.

2. Stake out your slab location.

3. Dig out enough soil for your gravel sub-base.

4. Pack the gravel fill.

5. Prepare your set concrete forms. How thick should your concrete slab be? That really depends on how you intend to use your metal building, but 4-6 inches is generally a good range to shoot for. 4 inches is fine for light loads, while 6 inches is preferred for heavier loads like an RV.

6. Place rebar to reinforce the slab.

7. Mix and pour the concrete.

8. Screed and float the wet concrete.

9. Use a push broom to create texture on the surface of your slab, if desired.

10. Allow concrete to cure, and remove forms.

Get Your Best Custom Metal Building from WZH!

Installing a custom metal building really is the best choice. Make sure you’re getting the best product from the best provider – choose WZH! We deliver and install in 46 states at NO extra charge, and we’re also happy to offer precision-engineered metal building kits you can pick up and install yourself for an additional discount on your building purchase. Our metal building kits come with all the materials you need for building installation, including framing, paneling, trim, fasteners, and foundation-specific anchors.

We also happen to offer the best metal building financing and RTO payment plans you’ll find anywhere!

Get in touch with one of our friendly building specialists today at (980) 819-4368, and experience the WZH difference! We do more than just sell metal buildings; we’re here to provide shelter for your way of life. At WZH, what’s Central to you, is Central to us.