Building types · Bonneville, Jefferson & Bingham counties
Idaho exempts farm buildings from the state building code. The exemption is narrower than most owners assume, and the county still regulates the parcel, the use and the setbacks.
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Acreage, plus what will be stored inside. Those two facts decide whether the exemption is open to you.
Idaho Code §39-4105 exempts farm buildings from the state building code. That is a real exemption and it removes a real cost. It is also the point where a lot of projects go sideways, because owners read it as permission to build without oversight.
An ag-exempt building is not an unregulated building. The state code steps back; county zoning does not. In Bonneville County the terms are written down.
Bonneville County Code §156.040 sets the qualifying conditions: the parcel must be an agricultural unit of 5 acres or more, and the structure must house farm implements, hay, grain, poultry or livestock. The building must not be used for human habitation, as a place of employment where products are processed, or for public use. The owner signs a compliance statement affirming all of it.
A zoning permit and setbacks still apply. Bonneville zoning requires a permit for any structure with a completed value of $100 or more — a threshold no building meets its way out of.
Verify the current text and your own parcel with Bonneville County Planning & Zoning, or with Jefferson or Bingham County if your parcel sits there. Terms differ by county.
The common plan is to put up an exempt building now and finish part of it as living space or a business later. That path exists, but it is not administrative. Changing the use requires a conversion permit, full compliance with the building code in force at the time of conversion, and an occupancy permit before the space is used.
Full current-code compliance on a building that was never engineered to it can mean insulation, egress, fire separation, electrical and structural work retrofitted into a finished shell. If habitation is anywhere in the plan, the cheaper decision is to design for it now. That is the whole subject of the barndominium shells page.
The production numbers explain the large buildings. Bingham County is Idaho’s number one county for both vegetables and potatoes at $230.6 million and grains and oilseeds at $146.5 million. Bonneville runs 893 farms across 406,594 acres, Jefferson 679 farms across 262,180 acres.
The acreage distribution explains the small ones. In all three counties the majority of farms are under 50 acres. That is a lot of owners with a tractor, a hay supply, a few head of livestock and nowhere dry to put any of it — and a lot of parcels sitting right at or below the 5-acre line the exemption depends on.
Which side of that line your parcel falls on changes the permit path before it changes anything about the building.
Driven by door clear height and turning room, not by floor area. A combine or a sprayer with folded booms sets the opening, and the sidewall has to exceed it.
Stacked hay puts real lateral pressure on the lower wall, and the stack height sets the eave. Ventilation matters more than insulation.
Moisture and ammonia are the design problem. Ridge and eave ventilation, corrosion resistant fasteners and a floor that drains outrank almost everything else.
Whatever the use, the snow load your jurisdiction adopts still governs the trusses. An exempt building is exempt from the code review, not from the physics. See the snow load by town →
Shell-only scope with living space finished separately, which is where most bid confusion on this build type starts.
Added bays and covered wings, where drifting snow against the taller wall raises the design load on the lower roof.
Acreage and intended use settle it, so include both with the address. Plenty of buildings people assume are exempt turn out not to be, and it is far cheaper to learn that now.