30' x 40' · 1,200 sq ft footprint

30x40 Barndominium Floor Plans in Indiana

A 30x40 barndominium is a 1,200-square-foot steel-sided or post-frame home: one clear-span shell, two or three bedrooms, and a great room under the open truss line. We build it as a complete house, not a garage with a bedroom in it — the footings go to the depth your county's row in the state code table demands, the walls are insulated to your climate zone, and the plan is drawn around the lot and the zoning district it will actually sit in. The questions that decide a 30x40 in Indiana are rarely structural. They are whether the building is the house or a second building on the parcel, and whether 1,200 square feet clears the zoning ordinance's minimum or overshoots its accessory-dwelling cap. Start with the project survey and we will settle those before anything is drawn.

Start your project

What actually changes at this size

The dimensions are the easy part. These are the decisions that follow from them.

Minimum dwelling size: 1,200 square feet is a threshold, not a comfortable margin

As a principal home, a 30x40 is sized right at the line in some districts. Boone County's Table 3 lists a one-storey minimum ground floor area of 1,200 square feet in the AG, RE, R1, R2 and PB columns and 900 in R3 and R4, with multi-storey minimums of 900 and 750 respectively. Johnson County's UDO sets 900 square feet in AG (on a two-acre, 200-foot-wide minimum lot) and AR, and 1,600 in SR. Where a minimum sits exactly at 1,200, how the ordinance measures floor area — outside of wall or inside, with or without a porch — is the whole question, so we get the administrator's reading in writing before the drawings are fixed. Adding a loft is the usual way to put a 30x40 comfortably over a threshold without enlarging the slab.

As a second dwelling, the caps start below 1,200

Both counties allow a detached accessory dwelling unit, and both cap it. Johnson County's UDO sets a detached unit at a minimum of 220 and a maximum of 1,000 square feet, one per parcel, no taller than 25 feet or the primary dwelling, behind the front façade, on the house's existing driveway and never under separate ownership. Boone County's accessory dwelling standards set a 400-square-foot minimum and a maximum of the lesser of 1,500 square feet or 50 percent of the primary dwelling unit's footprint, allow no more than two bedrooms, require a special exception before a building permit is applied for, and require deed restrictions recorded to hold the standards in perpetuity. So a full 1,200-square-foot living 30x40 is over the line in Johnson County, and in Boone County it needs a primary house with a footprint of at least 2,400 square feet.

As a garage or shop, living space needs its own permission

Boone County's ordinance says living quarters are not permitted within an accessory structure without a variance from the Board of Zoning Appeals, and defines living quarters as permanent or roughed-in provisions for sleeping, cooking and sanitation. It also classes any accessory structure with a bathroom, kitchen or living area as an accessory dwelling unless a use affidavit is recorded, and it caps a single accessory structure in the AG district at 3,000 square feet with 4,000 cumulative where the property's primary use is residential. On the code side, the Indiana Residential Code's own garage section, R309.6, says any habitable area inside a detached garage or accessory structure must meet all applicable sections of the code, with an exit door or window under R310 and R311. A roughed-in bathroom is where a shop quietly becomes a dwelling in both documents.

Footings to your county's row, not to a shop-building habit

The Indiana Residential Code lets a freestanding accessory structure of 721 square feet or less skip frost protection when it is built to Table R309 — a 30x40 is 1,200 square feet, so it never qualifies, whether it is a house or a shop. Its footings go below the frost line printed for its county in 675 IAC 14-4.4 Table R301.2(1): 30 inches in Boone and Johnson counties, 36 inches in Allen County, 24 inches in Monroe County. The same table sets ground snow load at 20 psf in all four. We price the foundation from that row and from a test hole in the footprint, never from a generic kit drawing.

House or second building

The same 1,200 square feet passes in one Indiana district and fails in the next

Indiana's building rules are uniform — the 2020 Indiana Residential Code, 675 IAC 14-4.4, applies in every location in the state, and local units may not adopt anything stricter. Zoning is different. Local zoning ordinances are expressly carved out of that no-stricter rule, so the size tests a 30x40 has to pass are written county by county, and two neighbouring counties south and north-west of Indianapolis show how far apart they sit. Boone County's zoning ordinance, Table 3, sets a minimum ground floor area of 1,200 square feet for a one-storey single-family home in its AG, RE, R1 and R2 districts — a 30x40 meets it exactly, with nothing to spare — and 900 square feet for a multi-storey home. Johnson County's Unified Development Ordinance sets a 900-square-foot minimum dwelling size in its AG and AR districts, which a 30x40 clears easily, and 1,600 square feet in its SR single-family district, which a 30x40 does not reach at all. Build the same shell as a second dwelling behind an existing house and the tests flip from minimums to maximums: Johnson County caps a detached accessory dwelling unit at 1,000 square feet, and Boone County at the lesser of 1,500 square feet or half the primary dwelling's footprint. Which district your parcel is in is the first thing we establish.

How people actually split 1,200 sq ft

Common configurations we see at this footprint. Yours does not have to match one exactly — this is a starting point for the conversation, not a catalog.

Two-bedroom single-storey with open great room

1,200 sq ft on one level: 2 bedrooms, 2 baths, open kitchen and living

The plan most people picture: a 30-foot clear span with the great room under the high part of the ceiling and two bedrooms at one gable end. It is the most economical way to use the shell, and in a district whose one-storey minimum is exactly 1,200 square feet it is also the plan that needs the floor-area measurement confirmed first. If the parcel is on septic, sizing starts from the bedroom count, not the square footage.

Three bedrooms with a loft over the bedroom wing

1,200 sq ft main floor / about 400 sq ft loft

A loft over the bedroom end lifts the total comfortably past a 1,200-square-foot threshold without enlarging the foundation, and in Boone County it moves the plan onto the lower multi-storey minimum of 900. It needs a stair that meets the Indiana code's own riser and tread limits and a smoke alarm at the top of it. It is the plan we reach for when a family needs a third bedroom but the lot or the budget will not take a bigger slab.

Shop bay with a one-bedroom suite

800 sq ft shop / 400 sq ft one-bedroom suite

For a parcel that already has a house, or for someone living in the suite while a main home is planned. The suite at 400 square feet meets Boone County's accessory-dwelling minimum exactly, and the shop half stays a garage. Everything about this plan turns on the zoning classification, so it only moves forward once the county has said, in writing, how it will treat a building with both.

Ways to build this size

A 30' x 40' footprint can go together several ways. These are the service lines most relevant to it.

Custom Plans

Custom barndominium floor plans drawn for your Indiana lot, county and budget — shop bays, lofts and porches included. Start with a free plan survey.

Post-Frame Homes

Post-frame and pole barn homes for Indiana land — posts, trusses and girts designed to your county's frost and snow row. Start with a free project survey.

Permitting & Approvals

One residential code covers all of Indiana, but permits are local. We find which offices govern your parcel, then carry zoning, septic and building approvals.

30x40 Barndominium: common questions

7 questions we get asked most often about this footprint. If yours is not on the list, ask it directly.

Start your project

Is a 30x40 big enough to be the main house in Indiana?

It depends on the zoning district, because the minimum-size rules are local. In Boone County, Table 3 of the zoning ordinance requires a one-storey single-family home in the AG, RE, R1 and R2 districts to have at least 1,200 square feet of ground floor area — which a 30x40 meets exactly — and 900 for a multi-storey home. In Johnson County, the UDO's minimum dwelling size is 900 square feet in AG and AR and 1,600 in SR, so the same building passes easily on a farm parcel and fails in a single-family subdivision district. Ask the planning office for the minimum and how it is measured before you commit to the size.

Can I build a 30x40 as a guest house or in-law unit behind my house?

Usually, with limits that differ by county. Johnson County's UDO allows one detached accessory dwelling unit per parcel at 220 to 1,000 square feet, no taller than 25 feet or the primary dwelling, located behind the front façade and sharing the existing driveway. Boone County allows one accessory dwelling of 400 square feet up to the lesser of 1,500 square feet or half the primary home's footprint, with no more than two bedrooms, after a special exception and with deed restrictions recorded. A fully finished 30x40 is 1,200 square feet, so in Johnson County it has to be partly shop, and in Boone County the main house has to be large enough to carry it.

Does a 30x40 shop need frost footings?

Yes. The Indiana Residential Code's frost-protection section exempts only freestanding accessory structures of 721 square feet or less built to its Table R309, and a 30x40 is 1,200 square feet. Its footings go below the frost line listed for its county in 675 IAC 14-4.4 Table R301.2(1) — 24, 30 or 36 inches depending on where the land is. That applies whether the building is a shop, a garage or a home.

How deep do the footings go and what snow load is the roof built for?

Both numbers come from the county's row in 675 IAC 14-4.4 Table R301.2(1), which local units cannot raise. For example, the table sets 30 inches and 20 psf for Boone, Johnson, Hamilton and Marion counties; 36 inches and 20 psf for Allen County; 36 inches and 30 psf for Elkhart, Lake and St. Joseph counties; and 24 inches and 20 psf for Monroe and Vanderburgh counties. On a 30-foot span the snow figure is rarely what drives the cost; the footing depth and the soil under it usually are.

Will the county inspect my 30x40?

That depends entirely on where the land is. The 2020 Indiana Residential Code is in force everywhere in the state, but the Department of Homeland Security says residential structures fall under the jurisdiction of the local government entity, and where there is no local one the residential issue becomes a private civil matter. Many rural counties still require an improvement location permit under their zoning ordinance — Boone County requires one for garages, sheds and other structures over 50 square feet — and the county health department issues the septic permit separately. We build to the code either way and tell you which offices your parcel answers to.

What does a 30x40 need if the land is on septic?

A septic construction permit from the local health department before construction starts, sized by bedrooms rather than square feet. Indiana's residential on-site sewage rule, 410 IAC 6-8.3, sets design daily flow at 150 gallons per day per bedroom and a minimum septic tank of 750 gallons for two bedrooms or fewer and 1,000 gallons for three. The soils have to be described by a soil scientist, so a site visit belongs early in the schedule, not after the slab is poured.

Can I put living quarters in the shop half later?

Plan for it now rather than later, because both codes treat it as a real change. Boone County requires a variance from the Board of Zoning Appeals for living quarters in an accessory structure and counts roughed-in provisions for sleeping, cooking and sanitation as living quarters. The Indiana code requires any habitable area inside a detached garage or accessory structure to meet all applicable sections of the code, including an emergency escape opening. The septic rule also requires a new permit before plumbing is added to a residential outbuilding. If a suite is in the plan, we frame, insulate and rough it in on the first permit.

Want this drawn for your program and your parcel? That is where a build actually starts.

Start your project

Sources

Start your plans

Tell us what you want to build and we will draw a 30' x 40' building for your program, then confirm what it looks like on your parcel, which office permits it, and a realistic budget range. That conversation costs nothing.

Start your project