Alan’s Metal Building Buyer's Guide

Jesus once said that a wise man builds his house on solid rock. In the same way, a smart homeowner ensures their metal building sits on a concrete slab.

If your local building department permits it, you have a few foundation options for your metal building. It can be installed directly on the ground or on a gravel base, where installers can secure it using rebar or mobile home anchors. A dirt or gravel foundation may work well for storing farm equipment or garden tools, but if you plan to park vehicles inside, concrete is your best choice.

On my website, you might notice the option to place your building on an asphalt foundation. This is generally recommended for carports. However, asphalt emits a chemical odor and isn’t the best choice for fully enclosed metal buildings without proper ventilation.

Your foundation will likely be the second most expensive part of your overall project. If you’re worried that foundation costs could push your metal building out of budget, check out the do-it-yourself tips I’ve included at the end of this chapter.

Have an Existing Foundation?

If you have an existing foundation, you might be able to use it for your new garage. Check with your local building department to verify that it meets local building codes. If you’re ordering a garage from Alan’s Factory Outlet, the foundation should usually be at least a foot wider and a foot longer than the dimensions of your garage. This will allow the garage to be securely bolted to your foundation.

Specs for Pricing a New Slab

To get precise cost estimates for your foundation, you need to be familiar with key details about metal building slabs. This will help you ask the right questions when consulting contractors. Understanding foundation basics will also make it easier to determine whether a contractor is experienced or not.

Thickness. A four inch thick concrete slab with footers is suitable for most metal building foundations, but local codes may require a thicker slab. Additionally, a footing is often required, so it’s important to check with local building codes to ensure compliance. If you plan to store heavier vehicles, such as an RV, you’ll need a foundation that is at least six inches thick.

If you will be using heavy-duty floor jacks to lift vehicles in your garage, you may need additional support in the areas where you will place the jacks. Discuss your specific load requirements with a concrete contractor.

Footings. The outer edges of your concrete slab need to be thicker than the main pad to create a footing that supports the metal building’s walls. Most local regulations require footings to be at least 12 inches deep and 12 inches wide. If your area has unstable soil or a low frost line, you may need deeper footings to provide additional support.

Slope. Your foundation slab should be completely level to ensure a stable installation, smooth door operation, and an even work surface. A level slab is also the most cost-efficient option.

If you’ve noticed that some attached metal buildings have a slight slope from back to front, it’s designed for drainage. These structures often house water heaters or washing machines that might need drainage during maintenance. However, for a detached building, a level foundation is preferable. If you occasionally need to clean the floor, a squeegee can help remove excess water

Size. Most of the metal buildings that I sell require a concrete slab that is one foot wider and one foot longer than the base of the garage. This ensures that the heavy-duty concrete bolts that anchor the garage to the ground won’t crack the concrete near the edges of the pad.

However, some of the garages I sell require a concrete pad that is the exact size of the base of the building. So I created a concrete pad size calculator that you can use to easily determine the right size of slab for a garage in your specific location.

Edges. In most locations, the engineers who design our garages recommend a concrete pad that is larger than the base (footprint) of the garage. Recommendations vary based on location and building size. You can use our concrete pad size calculator to get an initial understanding of the concrete pad required for your building.

If your concrete pad is larger than the base of your garage, it creates a 6-inch “curtain” around the edges of your garage. If this curtain is level with the rest of the foundation, water running down the outside walls of the garage will tend to pool around your garage and seep in under the bottom rail of the frame.

One method we’ve found to prevent this water leakage under the framing is to slope the 6-inch curtain downward very slightly. You can also step down the concrete by ¾ of an inch and create a ledge.

The person preparing the slab formwork can create a sloped or recessed ledge by placing six-inch boards inside the form, ¾ of an inch below the slab’s final height. If you prefer to keep the edges level with the rest of the slab, applying a concrete sealant around the base after installation will help prevent water from seeping into the structure.

Gravel. A base of compacted gravel provides a stable foundation for the concrete slab and also helps control moisture, preventing water from seeping into the foundation. I recommend leveling and compacting gravel before pouring the slab, though this step may not be required in all areas.

Vapor Barrier. Most contractors will place a vapor barrier on top of the gravel (or soil) before pouring the concrete. This serves two important functions:

1. It strengthens the slab by preventing water in the concrete from draining into the gravel while curing.
2. It reduces moisture from rising through the porous concrete and into your metal building. This is especially important if you don’t plan to have gravel under your concrete slab.

Apron. You’ll likely need a concrete apron at the front of your metal building to act as a ramp up to the slab, which should sit a few inches above ground level. If you also want a driveway, now is the best time to decide how large you want it to be.

Get Quotes

The best way to start is by calling a nearby Ready Mix supplier. Speak with the concrete dispatcher and ask for recommendations on the top two or three concrete slab contractors in your area. These suppliers work with all contractors and usually know who does quality work.

If you can’t get recommendations from a concrete supplier, try searching online for “concrete contractor near me.” Your search will bring up many third-party platforms like HomeAdvisor, Angi, Thumbtack, and Handy. These sites let you request quotes from local professionals by filling out a form.

What you may not realize is that these platforms sell your contact info to multiple contractors. Each contractor has to pay fees that can exceed $100 just to call you. If one of these platforms gives you a list of local businesses, a better approach is to look up each company’s website or phone number directly and contact them yourself—without using their forms.

Key Questions to Ask When Calling a Contractor:

• Ask if they pour foundations for detached metal buildings.
• Find out how many metal building and carport foundations they install per year.
• Explain your project and ask for their professional recommendations.
• Ask if they pour foundations for detached metal buildings.
• Ask if they recommend gravel and/or a vapor barrier.
• Ask how they cure the concrete after it is poured.
• Get a quote. Make sure you know what is and is not included in the quote.
• Ask for some recent references (homeowners who they poured a metal building floor for).

Let each contractor talk long enough for you to gauge whether they’re a good fit for the job. Take detailed notes so you’ll remember who to contact when you’re ready to move forward.

Want to Do It Yourself?

Labor costs make up the biggest portion of your metal building foundation’s price. If hiring a professional isn’t within your budget, doing the work yourself could cut costs in half.

However, since the foundation is a crucial structural component, mistakes can be costly

If you have the time and are willing to learn, here are two key steps to take before attempting to pour your own foundation:

Use a concrete slab calculator and a slab installation cost calculator to determine how much material you’ll need and estimate the cost. It’s wise to set aside extra funds for unforeseen expenses.

It’s best to gain insight from an expert to avoid costly errors. Mike Day offers an online concrete slab course at a reasonable price. The course includes a money-back guarantee—if you decide the work is too complex after taking the course, you can request a refund.