Barndominium Foundations: 5 Types To Know

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A barndominium or “barndo” can be a few things. It’s a preexisting agricultural building renovated and converted into a domestic house. Alternatively, it’s a modern building designed in a rustic style to copy a typical American barn.

Usually, but not always, new-build barndos come as kits erected onto a purpose-made foundation. However, before construction, you must design the barndominium foundations, considering the soil conditions, local climate, and the size and weight of the structure.

This resource explains the different types of foundations available and how you choose which one to use.

Table of Contents

Barndominium Foundation Overview

A barndominium’s foundation is the base on which you build the barndo kit and which supports the structure’s weight and the items you keep in it.

Typically, the foundation consists of a concrete slab (although other types exist) of 4″ to 6″ thick concrete with the perimeter made from much deeper footings. The footings support the load-bearing outer walls and must be deep enough to comply with the local building codes.

Footings and foundations are essential for a stable barndominium; you must make them as good as possible.

Consequently, it would be best if you always left it to a structural engineer to design the foundation and a professional contractor to excavate the trenches and pour the concrete, adding the reinforcing as necessary.

Then, you’ll have something complying with the codes and a home safe enough for you and your family.

How Are Barndo Foundations Different?Β 

Every foundation is different, and a qualified professional must design them for the ground conditions existing at the time.

However, most foundations used by a conventionally built house consist of footings around the perimeter of the building’s footprint and wherever there are load-bearing walls within the structure.

On these, the contractor lays bricks to floor level and generally fills the uncovered soil with concrete.

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In contrast, a barndominium typically uses a slab foundation, at least the dimensions of the house, with the outer 2-3 ft. perimeter footings supporting its weight with no other load-bearing walls.

Contractors pour both footings and slab concrete simultaneously, making the cured concrete one unbroken unit, thus giving better support and stability. Furthermore, the barndo’s steel skeleton will be supported by steel posts concreted into the footings.

Barndominium Foundation Requirements

As we’ve just said, the foundations’ requirements differ depending on the ground conditions, water table, and other factors unique to your locality.

Therefore, you must adapt the information presented in this article to suit your state, local building codes, and location within the local authority’s jurisdiction.

However, the only differences are generally the footing’s excavation depth and concrete volume. A qualified structural engineer certified to work in your state and guided by the local building codes is the only person who can decide the type of foundation.

Concrete Specifications

All barndominiums must comply with the building codes and be attached to concrete footings.

Generally, concrete is susceptible to below-freezing temperatures, so depending on where you live, footings must be deeper than the distance you’ll read in this article and elsewhere.

So, use the local building codes to provide information on footing excavation depths and concrete thickness.

Concrete Slabs

The following information is for general reference to help you in your research.

Check with your local building permit office for actual requirements.

Slab Area

Slabs should be at least 6″ longer in width and length than the dimensions of your kit.

Therefore, for a 40ft x 30ft building, you should construct a 40ft 6ins x 30ft 6ins slab.

Slab Thickness

For a domestic barndo, the concrete floor should be at least 4″ thick with the top surface level. Typically, the concrete strength should be at least 2,500 psi.

However, suppose you intend to store heavy machinery or vehicles on the barndo’s first floor.

In that case, consider increasing the concrete thickness to 6″ minimum, with a strength of 4,000 psi. Reinforce the concrete with fiber mesh at the concrete batch plant or install #3 steel rebar at 24″ centers.

As we’ve said previously, these specifications will vary depending on various factors, and a structural engineer should design them guided by local building codes. Furthermore, the concrete should be poured by a professional contractor using accepted construction practices.

Prices for 4″ thick concrete vary depending on where you live. But you can expect to pay around $4.00/sq.ft.

Footings

Although the slab is an integral part of the foundation, it’s not what supports the barndo’s weight. For this, you need the footings which extend deeper into the ground and distribute the barndo’s weight into the surrounding soil.

Pour perimeter footings simultaneously with the slab, so they’re one continuous mass, known as a monolithic pour (or monolithic slab). Considering the ground conditions, the foundations for a single-story barndo should be 12″ wide and extend at least 12″ below the frost line.

However, additional floors need larger-sized footings, reinforced with continuous runs of #4 steel rebar along the trench’s bottom and top. Generally, 12″ x 12″ footing costs around $17 per running foot.Β But, once again, confirm this with your structural engineer.

These drawings from Absolute Steel explain this better than hundreds of words.

These footing dimensions don’t apply to small accessory structures like sheds, decks, or porches smaller than a specific area as specified in your local building codes.

Resale Value Implications

A house without a suitable foundation won’t have many buyers, as no one knows when the building will collapse. Furthermore, no lender will finance the purchase of a property with poor footings and incorrectly built foundations.

So, it makes sense to comply with building codes at the beginning and regularly inspect and maintain the foundations during their lifespan.

Longevity and Durability Concerns

A property with a good foundation will last a considerable amount of time, possibly a hundred years or more. In contrast, a poor foundation built without building code compliance will probably last only a few years before the concrete crumbles and severe subsidence occurs.

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Therefore, it makes sense to design and build correctly in the first instance and keep the concrete inspected and maintained throughout its lifespan.

Overall Structural Integrity of Barndominiums

Because the monolithic foundation slab and footings are poured as a single item and reinforced correctly, any ground movement should have minimal effect on the building’s stability.

A barndo’s structural integrity depends on the strength and stability of the foundations.

Ensure they’re designed by a qualified structural engineer in line with local building codes and constructed by an experienced contractor using best practices.

Building Code Basics

Complying with the local building codes will ensure any building’s structural integrity, including your barndo. The regulations derive from the International Building Codes for 1- and 2-story residences and can be summarized as follows.Β 

Each construction project is unique, and the foundations depend on the load-bearing properties of the local soil. Therefore, code rules are always set locally and enforced by the local inspectors, usually employed by the town’s building department.

All US states use the International Building Codes (IBC), updated every three years. The current version, ICC IBC-2021, will be updated in 2024.

However, the codes are merely guidelines and recommendations. The local building code offices base the local construction law on these guidelines but adapt them by omitting, modifying, or expanding them to suit local conditions and the existing legal requirements.

3 Types of Barndominium Foundations

Although concrete slabs are the usual foundation type when building a barndo, there are other foundations depending on your preferences and the kind of ground present at the site.

1. Slab or Slab-on-Grade Foundation

Slab foundations are the most uncomplicated and affordable barndominium foundations and usually include a thermal insulating layer to protect against losing heat to the colder ground.

Generally, slab foundations better suit flat lots and hot, wet, and humid regions such as Florida than other foundation types because they’re less likely to suffer from structural damage in areas where the ground freezes.

However, check with the local building codes because some specify that foundation spaces must have ventilation, which a slab cannot.

Typically, barndominium frames use steel posts as the basis of their skeleton, secured to the perimeter concrete footings that form part of the slab. Generally, slabs cost around $4/sq. ft.

2. Crawl Space or Pier-and-Beam Foundations

A crawl space or pier-and-beam foundation has exterior concrete walls at least 18″ above ground level or grade, supporting a suspended floor. The floor has piers and beams underneath the joists, effectively reducing the floor’s span.

However, each supporting pier must have a concrete footing to spread the load above. The space between concrete and floor joists provides access to plumbing and cabling, should they need maintenance in the future.

Crawl spaces may work better in cold and dry areas as the depth of the frost line determines the depth of footings. For example, in Kansas, where the frost line sometimes reaches 34″ below grade, the foundations need to be below this and supporting walls built up to grade.

Furthermore, crawl spaces work better on sloping ground because of the excessive excavation required to provide a level slab.

Crawl spaces allow you to add moisture barrier and extra thermal insulation like spray foam to the underside of the suspended floor while allowing free ventilation to the underground area.

Typically, a crawl space foundation can cost up to $7/sq. ft.

3. Basement Foundations in Barndominiums

There are various basement types, each with its own purpose.

Full Basement Foundation

A full basement is a crawlspace high enough to walk through. Access is usually by stairs within the house, and its floor is a concrete slab.

Generally, a basement isn’t classed as living space unless the surfaces are finished.

However, suppose you use it as a living area, a bedroom, or a kids’ playroom. In that case, you must add a fire escape in the form of a special window or door with access to ground level outside the barndo’s perimeter.

If you include a full basement below your barndo, it’s relatively expensive. You must excavate a large amount of soil and have longer barndo support posts extending to the deeper footings or build supporting masonry walls up to grade.

Not only do the materials cost more, but also the project’s timeline increases accordingly. Generally, a full unfinished basement costs around $10-$20/sq. ft. or more if you finish the surfaces.

Walkout Basement Foundation

You can build walkout basements under barndos constructed on steep slopes. One end of the basement starts at the top of the hill, while the basement’s other end is at the slope’s bottom, where there’s an entrance door.

Typically, construction methods and prices are similar to a full basement.

Partial Basement Foundations

We construct a partial basement within the perimeter of the existing foundations so the excavation doesn’t affect the barndominium’s footings and frame.

Depending on the partial basement’s floor area, you may have to include pier and beam supports to reduce the suspended floor’s span.

Factors Affecting Barndo Foundation Choices

Every foundation, regardless of its design, must fulfill the following objectives:

  • Increase the building’s structural stability.
  • Avoid the effects of unequal ground settlement.
  • Distribute the structure’s weight over a larger area of soil, thus reducing the load applied on each square foot of ground.
  • Prevent the building’s lateral movement.

The following factors achieve these goals.

Soil Type and the Right Barndo Foundation

The soil type at the building’s location is critical when choosing the correct foundation type, as it can significantly affect its performance.

Every soil type has varying load strengths, capacity, settlement characteristics, and drainage capabilities.

For example, soils with a large amount of clay shrink and expand as their moisture content varies. In comparison, sandy soils have good drainage but have poor load-bearing characteristics.

Therefore, a geotechnical engineer must conduct a thorough soil analysis to help the structural engineer choose the foundation suitable for your barndominium.

Building Codes

Building codes and associated regulations are essential to ensure the structure complies with necessary safety standards. Municipalities set local building codes to reflect the conditions and existing laws in their locality, thus guaranteeing safe construction projects.

Research the local building codes before choosing a foundation type to see which are legal. Failure to do this will result in fines and other penalties.

Climate and Environmental Impacts

To ensure you’re up-to-date with existing ways of thinking, you must consider the environmental impact of each foundation type. For example:

  • Traditional concrete foundations use cement with a higher carbon footprint than other foundation types.
  • Other options will minimize your environmental impact, such as using reclaimed and recycled materials like permeable pavers.

It’s not only environmental concerns you should worry about. Your region’s climate can cause issues, too:

  • If you live in an earthquake-prone region, consider a suitable foundation that can withstand seismic disturbances.
  • If you live in an area with frequent flooding, ensure the barndo’s foundations have efficient drainage and water-resistant features.

These and other factors will help determine whether a slab, pier-and-beam, or hybrid foundation is feasible. However, let a professional decide which foundation is best.

Energy Efficiency

Energy efficiency awareness is a top priority for most homeowners as it saves money, and the selected foundation can play a massive part in your home’s energy performance.

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Certain foundation types, such as foamed concrete slabs, insulated concrete, and sprayed foam on the underside of suspended flooring, lead to a more energy-efficient barndominium and subsequent cost savings.

Project Timeline

The overall timeline of your barndo project will vary with the type of foundation you choose.

If the local building codes allow it, choose a foundation type that speeds up the project and reduces labor costs.

Foundation Durability & Maintenance

Once the foundation is in place, the house constructed, and you’ve moved in, the last thing you want is to carry out repairs and maintenance on the foundation. Therefore, its durability is a crucial factor.

Consider the long-term implications of choosing various foundation types (if the building codes allow a choice) and their durability, especially the foundation’s resistance to settlement and cracking. Consider foundations that are durable and have a proven performance in your locality.

Even if you choose the best possible foundation for your area, they might still require regular inspections to ensure nothing goes wrong. And if they need inspections, they might need repairs and maintenance to maintain their durability.

For example, a pillar-and-beam foundation may need ventilation and insulation maintenance in the crawlspace. Furthermore, slab-on-grade foundations may need periodic resealing to prevent water ingress.

Understand the requirements of each foundation type so you can budget accordingly.

Cost Considerations

A foundation’s cost is a significant factor in your new barndo’s construction budget. Each foundation type has its unique cost and will vary significantly, some being more affordable than others. And, of course, consider the cost of inspection, repair, and maintenance.

Balancing the durability of the foundation with its cost-effectiveness will help you make the right decision. However, if your local building codes specify a foundation with no leeway, you have no choice but to comply.

Building Design

Your barndominium’s design and size are important when choosing a foundation. For example, a foundation for a single-story barndo differs significantly from a two or three-story structure.

Also, you must consider the necessary foundation changes if your design calls for a basement or a large open-plan room.

Common Foundation Challenges and Solutions

Dealing with Water Drainage

The most significant factor with water affecting your foundations is probably drainage. And I mean rainwater drainage management.

Rainwater management, or gutters, removes the concentration of high-volume rainwater from around the perimeter of the building where the foundations are. If the volume is a significant amount, you run the risk of affecting the ground supporting your footings.

Furthermore, a continual flood and drought cycle expands and shrinks the underlying soil, especially in a clay region, eventually degrading the soil and reducing its strength. This situation is valid for all foundation types, and you must consider it when choosing suitable rainwater management systems.

Gutters

If you don’t have gutters, install them immediately. But, if you do have them, ensure they work correctly by removing the silt and debris that washes off the roof surfaces.

How often have you seen weeds growing out of the gutter? The gutters probably aren’t working correctly and haven’t been cleaned regularly.

Downspouts

Believe it or not, most downspouts empty their rainwater right next to the house, precisely where the foundation is. Ideally, the water should drain at least 8 ft. away from your house, which can look strange and be in the way of a typical busy house and garden.

The ideal situation is to empty the downspout into an underground drain, taking the water to a suitable location to safely soak into the soil.

Resloping

Grade the soil away from the house so that the water doesn’t collect near the walls and foundations.

Use Porous Surfaces

Change hard paving for porous surfaces like gravel to prevent standing water next to the house.

This allows the water to soak naturally into the ground over a larger area.

Addressing Foundation Cracks and Repairs

A property’s footings carry the entire weight of the house, so you don’t want to find cracks in the masonry. Fortunately, DIYers can fix many foundation cracks if they don’t jeopardize the property’s structural integrity.

The only way to know if this is what you’re up against is to have a structural engineer or foundation contractor inspect. However, there are some things you can look out for before you start to panic.

Hairline Cracks

Hairline cracks about the width of sewing thread aren’t anything to worry about. You usually find them around window and door openings or in basement corners.

They’re caused by normal concrete shrinkage as the masonry cures or by standard ground settling. However, hairline cracks can become wider if subjected to repeated ice freezing and thawing cycles, which will eventually cause masonry to crumble.

So, DIY fix it using suitable acrylic masonry paint to seal any gaps. However, keep an eye on the crack; if it gets wider or reappears after painting over it, monitor it and see how it changes over time.

Take photos or write on the wall the distance between two pencil marks. If the crack doesn’t expand over several months, it’s stable, and you can fill it with cement grout or epoxy.

Horizontal Cracks

Horizontal cracks or cracks following the grout line on brick or blocks aren’t usually anything to worry about. But you should fill them using a caulk or grout suitable for masonry walls.

However, if a horizontal crack exceeds 1/2″, call in a foundation contractor who may inspect to see if it’s a structural problem. If not, they will inject expanding epoxy grout. Otherwise, the issue needs fixing.

Properly Insulating Barndo Foundations

The type of insulation to use in your foundation depends on the climate zone where you live and the foundation type you’ve chosen.

However, the following is a good guide:

Slab-on-Grade Foundations

The simplest way to insulate a concrete slab from the cold ground is to cover the waterproof barrier with expanded polystyrene insulation before laying the rebar and pouring the concrete.

Pier-and-Beam Foundations

In addition to insulating the concrete floor using the same method as slab-on-grade, you can also use spray foam insulation, which will adhere to the underside of the suspended wooden floor.

As with all insulation, lay a vapor barrier to prevent issues from condensation and fill all plumbing and cabling holes with foam insulation.

The Cost of Building a Barndominium Foundation

The most essential step in constructing a barndominium is laying the foundation.

Suppose you’ve chosen a 60 ft. x 40 ft. (2,400 sq. ft.) concrete slab for your foundation. In this case, the cost will fall between $5.50-$13.50/sq. ft.Β Therefore, the slab’s approximate cost will be $13,200-$32,400.

However, as we’ve mentioned beforehand, some factors affect this price in addition to the cost of concrete, such as:

  • Lumber used in formwork
  • The amount of fiber mesh used in the slab
  • The cost of rebar and insulation
  • Whether you’re laying the concrete yourself or hiring contractors. However, with any but the most straightforward foundation slab, we recommend hiring contractors.
  • The strength of the concrete
  • The slab thickness

Additional Features

Any foundation includes items other than just concrete, such as the following:

  • Vapor barrier$0.50/sq. ft. – Vapor barriers limit the amount of condensation beneath the foundation. This moisture can cause structural issues such as cracks; building codes specify barriers for all habitable structures.
  • Wire mesh$0.45/sq. ft. – This reinforces the concrete. Mesh has an advantage over rebar as there is a degree of flexibility. Depending on your requirements, you can buy plain, galvanized or stainless steel mesh.
  • Site preparation$0.50-$1.30/sq. ft. – This includes removing vegetation and grading soil to create a level surface.
  • Thicker edges$1/sq. ft. – Typically 12″ thick, this improves the overall slab structural strength and is independent of the extra concrete depth needed for the footings.
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Remember that all costs are approximate and will vary depending on where you live, the quality of materials, and how much labor you hire.

Average Cost Breakdown by Foundation Type

It’s a good idea to compare the estimated average costs of different barndominium main foundation types.

Foundation TypeAverage Cost/sq. ft.Total Average Cost for a 2,400 sq. ft. BarndoNotes
Slab-on-Grade$5.50-$13.50$13,200-$32,400Affordable and versatile. However, it's not suitable for cold or wet locations.
Pier-and-Beam$7-$11.50$16,800-$27,600Suitable for frosty and flood-prone locations. Needs additional insulation and moisture barriers.
Full Basement$33+$79,200+Complex to design and build. Very expensive. But adds extra living space.

Hidden Expenses to Watch Out

Several hidden expenses can increase the cost of your barndo’s foundation. These include:

  • Foundation depth – Deeper foundations mean higher prices. However, often, you won’t have a choice. The building codes will specify the minimum depth. However, the actual depth can be significantly more depending on the soil stability and slope of the surface.
  • Ground preparation – You must clear the surface of vegetation and tree stumps. You will probably need soil testing or borehole analysis as well.
  • Waterproofing and drainage – In regions subject to excessive rainfall or flooding, you must install additional foundation protection.
  • Permits and inspections – Generally, you must pay for building permits and foundation inspections.
  • Finishing – If you choose a basement foundation and want to use it as an extra room, finish the surfaces with drywall and add insulation, flooring, cabling, and plumbing.

Cost-saving Tips for Your Barndo Foundation Project

We don’t recommend DIYers building foundations in any but the smallest area and most uncomplicated design. It’s much better to leave the job to a professional. However, there are other ways to save money.

DIY Foundations

One of the benefits of building a barndo cheaply is that DIYers can do many jobs. However, we don’t recommend pouring the foundations yourself.

Foundation slabs and footings are complex jobs requiring many years of experience and specialized knowledge. However, you could offer yourself to the contractor as unpaid labor under their supervision.

Choose the Correct Contractor

It’s essential to choose a contractor experienced with pouring the foundation type specified by the structural engineer.

They know how to solve issues that might crop up, make the foundation up to code, and be on hand to answer questions at the inspection phase.

Make a Building Floor Plan and Project Timeline

You must connect your barndo to utilities and drainage. Usually, this means entering the premises at the foundation level, especially with drainage. Therefore, you must know when to do specific jobs and in what order.

For example, call the drain contractor to install their rough work before pouring concrete. Ensuring everything is in place at the right time will make everything run smoothly.

Barndo Foundation Maintenance and Care

You need to organize regular inspections and maintenance to keep your barndo’s foundation in good condition.

Routine Checks and Preventative Measures

The following checklist may help determine what needs addressing on your foundation:

Exterior Inspection

  • Cracks – Examine surfaces for visible cracks and holes. Note their length, width, and orientation. This data helps determine their cause and whether they’re serious.
  • Vegetation – Typical vegetation to watch out for include vines and tree roots. These intruders can infiltrate the foundations and cause damage.
  • Settling – Watch out for signs of settlement. This may indicate that the foundation is tilting. Use a spirit level to check doors, windows, and wall alignment.
  • Bulges or bows – Pressure from the surrounding soil can cause bulges or bows in the foundations. Keep an eye out for these.
  • Drainage – Walk around the property and ensure water drains away from the walls, with no pools of standing water.
  • Foundation material – The foundations should be solid with no splitting, crumbling, or erosion.
  • Water damage – Note any issues with discoloration or efflorescence on the foundations. This can indicate water ingress.

Interior Inspection

  • Cracks – Inspect walls and ceilings for cracks and note sizes and orientation.
  • Floors – Uneven or sloping floors can indicate problems with the foundation.
  • Doors and windows – open and close doors and windows to check for smooth movement. If they jam or don’t close smoothly, there could be problems with the foundations.
  • Cracked tiles – Cracked wall or floor tiles can suggest foundation issues.
  • Countertops and cabinets – Check kitchen cabinets and countertops are horizontal. Unevenness can indicate issues with foundations.

Other Considerations

  • Utility disruptions – Look for problems with electrical cables or plumbing. Misalignment or disrupted services can indicate foundation problems.
  • Previous repairs – Pay attention to previous maintenance to ensure the damage hasn’t reappeared.

When to Seek Professional Help for Your Barndo Foundation

Many small cracks will be okay with DIY repairs.

However, suppose you see the cracks becoming larger or reappearing after previous repairs, or water seepage that you can’t fix by diverting rainwater from the surface. In that case, it’s time to call in a professional.

Generally, the first person to hire is a licensed structural engineer, who will inspect the situation and suggest a solution. They may suggest DIY or recommend a foundation contractor for more severe issues.

Pouring Foundation Yourself vs. Hiring Help

Theoretically, you can pour a foundation yourself.

However, laying a foundation is heavy and exhausting work that requires precision and skill. Therefore, without professional experience, you can end up with cracking and crumbling foundations.

So, it’s always better to hire professionals to build a foundation, as the entire building depends on it.

FAQs

How long does a typical Barndo foundation last?

There isn’t a definitive answer to this, as foundation lifespans depend on several factors.

However, if you’ve built the foundation according to the local building codes, had no severe seismic occurrences or flooding, and regularly inspected and maintained them, there’s no reason why they shouldn’t last for hundreds of years.

Are Barndominium foundations eco-friendly?

Most foundations tend to be made from concrete, which involves cement.

Cement manufacture is probably one of the least eco-friendly processes. However, because concrete lasts for decades, sometimes hundreds of years, its overall environmental footprint is very low.

Furthermore, concrete is also 100% recyclable and reusable at the end of its lifespan.

Suppose you decide to leave it underground after demolishing the structure. In that case, it won’t cause any contamination with the surrounding ecosystem. The weather and vegetation will gently erode the concrete to its original constituents, rock.

Can barndos have crawl spaces or basements?

Most barndominiums use slab-on-grade foundations, which don’t usually have crawlspaces.

However, you can use pier-and-beam foundations for crawl spaces and basements. These foundations allow access to plumbing, insulation, cabling, and foundations for maintenance, and you can add extra insulation to the underside of the suspended floor.

Furthermore, the footings extend farther into the ground below the frost line, ensuring less damage from cracking and soil shifting in cold regions. However, these foundations cost more to build in terms of materials and labor.

Next Steps

Its foundation keeps a barndominium stable against extreme climatic conditions and provides a durable base to build on. You can use several main types of foundations and even more subdivisions and hybrids to support your barndo. However, the local building codes will specify which types are allowed in your locality and provide the minimum specifications to ensure a safe and stable home. Finally, foundations aren’t something to build cheaply, with unskilled labor, as your home is only as good as its foundation. And with poor-quality footing, you can be sure your home won’t last very long.

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