A barndominium is a home built out of a converted metal barn or other agricultural building. Since barndominiums repurpose existing structures, they require some special considerations when it comes to foundations. The foundation needs to support the weight of the building above and keep it level and stable. In this article, we’ll look at the foundation requirements for barndominiums and the most common foundation types used.
What is a barndominium?
A barndominium is a house that is built by converting an existing barn or shed into a residential living space. The term “barndominium” combines the words “barn” and “condominium.”
Barndominiums have become increasingly popular in recent years as an affordable and unique home option. They allow homeowners to repurpose old agricultural buildings rather than demolish them. Barndominiums have a rustic, farmhouse charm while still providing modern amenities and finishes on the inside.
Since barndominiums make use of existing structures, they require some special considerations when it comes to structural support and foundations. But they can make beautiful, cozy homes when done right.
Do you need a special foundation for a barndominium?
In most cases, yes, you will need a new or reinforced foundation for a barndominium. Here’s why:
- Existing barn foundations are designed to support lighter roof and hay/equipment loads, not heavier living spaces.
- Home building codes require more robust foundations than agricultural buildings.
- The floors and walls will need additional support for drywall, plumbing, electrical, HVAC, etc.
- You want the home to be level and stable long-term.
Some key foundation requirements for barndominiums include:
- Withstanding heavier vertical loads from walls, floors, roof
- Providing lateral stability against winds and earthquakes
- Supporting drywall, utilities, kitchens, bathrooms, etc.
- Preventing cracking and settling issues over time
In some cases, the existing foundation may be reinforced if it is in good structural condition. But most barndominium conversions require a new foundation designed specifically to support a residential living space.
Main Types of Foundations for Barndominiums
Here are some of the most common foundation types used for barndominium homes:
Concrete Slab Foundation
A concrete slab on grade is a popular foundation choice for barndominiums. This involves pouring a thick concrete slab directly on the ground to support the home.
Slab foundations work well for barndominiums because:
- They provide excellent load-bearing strength.
- They are low maintenance and do not require crawl space access.
- They offer a smooth and level floor surface.
- They align well with barn and shop aesthetics.
Slabs should be at least 6 inches thick and reinforced with steel rebar. They require a base of compacted gravel fill for stability. The concrete slab can be poured within the footprint of the existing barn.
Stem Wall Foundation
A stem wall (or chain wall) foundation is another solid choice for barndominiums. This type has concrete footings and walls that support the perimeter of the structure.
Stem wall foundations provide:
- Reinforced support at key stress points.
- The ability to create a crawl space if desired.
- Shear strength against lateral and seismic forces.
They involve more complex forms and concrete work than a slab foundation. But stem walls give you perimeter access options and are very sturdy. The interior can be left as a dirt crawl space or poured with a concrete slab.
Pier and Beam Foundation
A pier and beam system is sometimes used for barndominiums as well. This uses footings, piers, and beams to support the structure.
Benefits of pier and beam foundations include:
- Allows for more flexibility if the barn floor is uneven.
- Elevates the home above grade for ventilation.
- The ability to skirt around the perimeter.
Pier and beam systems work well for elevated barndominium designs. They require more initial legwork to design and build. Load-bearing beams are typically made from steel or lumber to provide support.
Choosing the Best Foundation Type
When deciding on the right foundation system for your barndominium, there are several key factors to consider:
- Existing barn foundation – Assess the existing foundation and whether it can be reinforced and added onto, or needs a full replacement.
- Soil conditions – Clay, expansive soils, or sandy soils will determine what foundation type works best.
- Groundwater level – A high water table may dictate elevating the foundation above grade.
- Frost line depth – All footings must extend below the frost line to prevent shifting.
- Layout – Consider how the foundation design fits with your planned layout.
- Budget – Simple slab foundations tend to be the most affordable option.
Work closely with an engineer or foundation contractor to design the right foundation system for your specific barndominium based on these criteria.
Fortifying the Existing Barn Foundation
In some cases, the existing agricultural building foundation can be retrofitted and fortified to support a barndominium conversion. Here are some ways the foundation may be strengthened:
- Add supports and new footings around the perimeter.
- Install piers beneath support posts or beams.
- Reinforce critical connection points.
- Infill areas with compacted structural fill.
- Pour a new structural concrete slab over the existing floor.
Assessing the condition and type of existing foundation is key. Structural engineers can evaluate whether reinforcement is feasible or if a full replacement is needed.
Key Elements of Barndominium Foundations
All barndominium foundations should include these key elements:
Proper Footings
Concrete footings distribute structural loads and prevent settling. They must be sized appropriately and excavated below frost depth.
Adequate Reinforcing
Steel rebar and welded wire mesh reinforce the concrete to resist cracking and add strength.
Vapor Barriers
Vapor barrier films or membranes under the slab help prevent moisture issues.
Coarse Base Layer
A gravel base provides drainage and evens out the surface beneath slabs and footings.
Sufficient Thickness
Slabs and stem walls must be poured thick enough to handle building loads without sagging.
Control Joints
Control joints relieve stresses that can crack slabs by creating planned weak points.
Hiring Foundation Contractors
Unless you have poured extensive foundations before, it is wise to hire professional contractors to handle this key part of your barndominium build. Look for contractors with experience building agricultural and residential foundations in your area. They will be familiar with:
- Meeting building codes and standards.
- Excavation, forming, and concrete work.
- Accommodating plumbing and electrical.
- Adapting foundations to the barn structure.
- Reinforcing existing barn foundations if feasible.
A structural engineer can first assess the existing structure and design the foundation plan. Then the foundation contractors can execute this plan properly.
Cost to Install a Barndominium Foundation
On average, expect to pay $15-$30 per square foot for a new barndominium foundation. Here are some cost considerations that affect pricing:
- Simple slab foundations tend to be the most affordable option.
- Pier and beam systems typically cost more due to materials and labor.
- Stem wall foundations fall in the middle price-wise.
- Reinforcing an existing foundation costs less than replacing it.
- Foundation size, access, materials, and site prep also impact costs.
Get quotes from several foundation contractors before settling on a budget. Many factors specific to your barn and property affect overall foundation costs.
Barndominium Foundation Cost Table
Foundation Type | Total Cost per Square Foot |
---|---|
Concrete Slab | $15 – $20 |
Stem Wall | $20 – $25 |
Pier and Beam | $25 – $30 |
Reinforced Existing | $10 – $15 |
Permitting Requirements
Most jurisdictions require building permits for new foundations to ensure code compliance. The general permitting steps include:
- Submit foundation plans approved by a structural engineer.
- Apply for building permit from the local authority.
- Pay permit fees based on project scope.
- Schedule all required inspections for footing, forms, rebar, backfill, etc.
- Make any corrections noted during inspections.
- Receive final approval after the foundation passes inspection.
Building codes provide critical foundation construction guidelines to follow. Know your local permitting process and costs before beginning work.
Conclusion
Barndominiums require specially designed foundations to provide adequate structural support. Concrete slabs, stem walls, and pier and beam systems are common foundation solutions. Work with structural engineers and experienced contractors to ensure the foundation meets residential building code requirements. With proper planning and design, you can build a stable, durable barndominium foundation tailored to your specific project.