How Thick Should Your Barndominium Slab Be? (2024)

How Thick Should a Barndominium Concrete Slab Be?

How Thick Should Your Barndominium Slab Be? (2)

Barndominiums have been growing rapidly in popularity for their spacious, flexible and affordable homebuilding potential. But transforming an old barn or shed into a livable residence requires some structural adaptations – starting with an adequately thickened concrete slab foundation.

How Thick Should Your Barndominium Slab Be? (3)

Typical pole barns or steel sheds build upon dirt, gravel or very thin concrete pads just meant to keep the framing lifted off the ground. Converting these structures to barndominiums demands adding a reinforced slab to withstand occupant loading and anchor the walls. This raises the question – what slab thickness meets structural requirements without overbuilding?

How Thick Should Your Barndominium Slab Be? (4)

General Guidelines

For barndominiums up to 1,500 sq. ft., most recommendations fall between a 4” and 6″ thick slab. This accommodates moderate traffic and furnishings adequately without excessive concrete use. The steel perimeter beams of barndominium kits require less internal slab support than wood framing.

Larger or two-story barndominiums may benefit from 6” to 8” thicknesses to prevent cracking or sinking from heavier live/dead loads. Farmhouses styled for heavy equipment will also need reinforced 8″ slab sections. Maximum steel-framed barndominium size per IRC code reaches 5,000 sq. ft. before requiring special engineering.

How Thick Should Your Barndominium Slab Be? (5)

Other Slab Spec Factors

Beyond depth, proper steel reinforcement and drainage provisions also play key roles in achieving structural slab integrity:

– #4 rebar grid 12” on center each way
– 4”-6” compacted gravel base
– 6 mil polyethylene vapor barrier
– Wire mesh for added tensile strength

How Thick Should Your Barndominium Slab Be? (6)

Perimeter edge thickening further helps minimize cracking and separate slabs from exterior grade. Using an elevated floating slab system is another method to prevent moisture wicking and related foundation issues.

In short, 4”-6” offers the ideal balance of strength and economy for small-to-moderate barndominium builds. Evaluate larger footprints on an individual basis to determine if thicker design merits the extra cost. Careful gravel prep, reinforcement and moisture prevention also ensure the slab’s lasting structural stability as an adapted new home.

How Thick Should Your Barndominium Slab Be? (7)

Aaron Scott

Aaron Scott is a freelance writer and researcher that has written hundreds of articles for online companies in the area of construction, design, finance and automotive. He's a Southern boy that enjoys creek fishing, hunting and camping. He's rarely seen without his trusted beagle hound "Scooter"

How Thick Should Your Barndominium Slab Be? (2024)


How Thick Should Your Barndominium Slab Be? ›

For barndominiums up to 1,500 sq. ft., most recommendations fall between a 4” and 6″ thick slab. This accommodates moderate traffic and furnishings adequately without excessive concrete use. The steel perimeter beams of barndominium kits require less internal slab support than wood framing.

What is the best slab for a barndominium? ›

Slab Thickness

If you are planning to park large, heavy vehicles inside (such as trucks or larger RVs), you should consider making the slab 6″ thick, and using 4000-psi concrete. You may not need this for a kit home, but often times a barndominium may be used to store vehicles and heavy equipment.

Should I use a 4 or 6 inch concrete slab? ›

As the concrete driveway will deal with the traffic daily, it's essential to know the function of the concrete driveway, as it impacts the necessary thickness, durability, and stability of the concrete. The recommended thickness is 4″ to 6″ inches for residential driveways that only lightweight vehicles pass through.

What foundation is best for a barndominium? ›

Properly executed, an embedded perimeter beam concrete slab foundation formulated from high strength 5,000 PSI concrete mix designs provides ideal structural support for the tremendous clear spans and dynamic live loads generated over generations of family life within your barndo.

How thick should a slab be for a metal building? ›

Minimum of 4″ thick slab for normal residential use ( cars, light trucks, etc ). For commercial use, 5″ or 6″ thick slab is recommended (heavy machinery) Footing must be of 42″ in depth although some local codes allow for less depth.

How much does it cost to pour a 40x60 concrete slab? ›

How much does a 40×60 concrete slab cost? It would be about $8,500 to $12,000 for a 40×60 foot concrete slab, 6 inches thick. That's based on national averages of around $5 per square foot for a fully engineered, finished concrete slab, including labor and materials.

What is the most expensive part of a barndominium? ›

What is the most expensive part of building a barndominium? The most expensive part of building a barndominium is often the interior finishes. Customization, high-end materials, and intricate designs can significantly impact the overall cost.

Do I need rebar for a 4-inch slab? ›

If your slab is under 5-inches deep, or if you plan to use it as a patio, sidewalk, or garden pad, you'll likely be fine without it. You could opt in for a welded wire mesh instead of rebar.

Will a 6 concrete slab crack? ›

Panels with excessive length-to-width ratios are likely to crack at the mid-panel point or at some other location between joints. The recommended joint spacing in feet is usually two to three times the slab thickness in inches. Thus, for a 6-inch-thick slab the maximum recommended joint spacing is 18 feet.

Is thicker concrete less likely to crack? ›

Is thicker concrete more or less likely to crack? Thicker concrete is less likely to crack due to extreme weather changes.

What makes a barndominium cheaper to build? ›

Barndominiums have a quality that often makes them very customizable, which is that typical barndominiums are often constructed from a metal building. Metal structures are usually less expensive to construct than traditional buildings, which is one reason why they are used so much in commercial construction.

Do you need a vapor barrier on a barndominium? ›

As many barndominiums are constructed from metal, a vapor barrier tape will help prevent potentially damaging condensation from entering the structure. Reducing the energy costs to heat the home. Many barndominiums often have vaulted or cathedral ceilings, meaning the ceilings are not parallel to the floor.

Are there load bearing walls in a barndominium? ›

A barndominium floor plan is very different from traditional homes, which must be designed with load bearing walls that limit creativity and possibilities. A barndo's steel framing eliminates the need for load bearing walls, making it easy to split a home into flexible living quarters and working spaces.

How much does it cost to pour a 30x40 slab? ›

The average cost is $4 to $8 per square foot. The median price is about $6 per square foot. Based on these averages, you may pay $4,800 to $9,600 with a median estimate of $7,200.

What happens if slab is too thick? ›

If the slab is too thin, it may break under load and fail before its time. If the slab is too thick, it costs more than it should. Slab thickness is a major factor in the cost of a concrete floor, so there's often pressure, which can become intense, to make the slab as thin as possible.

Is a 4 inch slab thick enough? ›

It's also important that a slab be thick enough to be durable. The thickness depends on what you'll be using the slab for. Concrete driveways and patios need to be at least 4 inches thick, whereas concrete countertops only need to be one and a half inches thick.

What is the best slab for a metal building? ›

How Thick Should A Concrete Slab Be For A Metal Building? Your concrete foundation for a metal building will be a minimum of 4″ thick. However, if you're planning to use your metal building to store heavy vehicles and equipment, we will recommend a 6″ slab.

What is the best type of metal building for a barndominium? ›

Steel represents the ideal choice for barndominium builders, as it strikes the perfect balance of being cost-effective, quick to erect, and exceptionally durable. When you consider the pros and cons of all of the options available to you, steel wins out in just about every category.

What kind of flooring do you put in a barndominium? ›

Many barndominium floor plans even include a focus on sustainable concrete flooring finishes such as polished concrete floors, epoxy floors, and stained concrete floors which naturally feature many of the same advantages in craftsmanship and longevity that make the barndominium so popular in the first place.

Can you build a barndominium on an existing slab? ›

Barndominiums are an increasingly popular and versatile housing option, and are often constructed on slab foundations, especially when using steel frames.

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