Does a barndominium kit price tell you what the finished house will cost?
Published
Summary
No. A kit price is what the seller charges for the parts it ships, and it leaves out designing the building for your county's loads, permitting it as a house, and the insulation, moisture control, mechanical systems and interiors it needs to pass inspection. A barn put up under an agricultural permit exemption can't just be moved into later either, since Oregon, for one, requires a building permit before a farm building becomes a home.
Your county sets the loads the frame has to carry
Beaver County, Utah, is a good example of how specific this gets. Every residential plan there has to be designed to the county's criteria:
| Design criterion | Beaver County requirement |
|---|---|
| Roof snow load | 30 lb |
| Frost depth | 30 inches |
| Seismic | Zone D |
| Wind | 90 mph three-second gust, exposure C |
Homes with 2,500 square feet or more on the main floor and more than one story need construction documents stamped by a licensed structural engineer or architect, and the building official can require stamps on other homes with unusual design features. The permit package also needs the truss manufacturer's design and layout with bracing and engineering specs.
A kit sold online was designed for some set of loads. If the seller can't tell you which ones, you can't tell whether the frame works in your county, and heavier snow or wind can mean bigger members and a bigger foundation than the kit includes. How much of a typical new house goes to foundations, mechanical systems and interior finishes is on the existing cost-to-build page.
The agricultural exemption doesn't cover a house
Putting the building up as a farm structure and finishing it as living space later doesn't work in Oregon. The state's Building Codes Division rules it out in its farm building exemption form. The owner signs a statement that if the building is used for or converted to a non-agricultural use, such as a garage or home occupancy, a building permit must be obtained before the conversion. State law, ORS 455.315, says an agricultural building does not mean a dwelling.
The exemption is narrower than it sounds, too. It applies only to the structural permit; electrical, mechanical, plumbing and septic work still need their own permits.
Metal walls hold moisture in
DOE's Building America Solution Center lists sheet metal among Class I vapor retarders, the materials that let almost no water vapor through. The same guide notes that condensation can form inside a home where warm air meets cool surfaces, and that over time the dampness can ruin insulation and lead to mold and rotted framing. DOE's Energy Saver pages add that insulation's R-value depends partly on moisture, and that heat flows readily through framing members, which is called thermal bridging.
Living in a metal building means designing the insulation, air sealing and drying paths together, and the materials and labor for that sit outside the kit price.