30' x 40' · 1,200 sq ft footprint

30x40 Barndominium Floor Plans in Oregon

A 30x40 gives 1,200 square feet on one level: enough for two bedrooms and two baths, or three compact bedrooms, with an open kitchen and living room. It is a popular first house on an Oregon acreage, a retirement home, or a starter plan that can grow later with a second storey or an attached garage. Because it sits close to the size limits that rural land-use rules use for second homes, the first question in Oregon is not the layout but what role the house will play on the parcel.

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What actually changes at this size

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

Two bedrooms, or three tight ones

The 30-foot width suits a central living space with bedrooms at each end. Two bedrooms and two baths fit comfortably; three bedrooms fit if the bedrooms are kept compact and the laundry shares the mudroom. Each bedroom needs an emergency escape and rescue opening of at least 5.7 square feet net clear, so plan the bedroom walls where windows can go.

Septic sized for the bedrooms you draw

Oregon's onsite rules, OAR 340-071, count as a bedroom any room the building department accepts as one, and set a minimum 1,000-gallon tank for four bedrooms or fewer. The site evaluation, with its test pits, is the first step toward the septic permit and comes before the plan is final.

A compact envelope is easy to insulate

A 30x40 has little wall and roof for its floor area. The ORSC energy chapter sets the insulation and window values for the edition your permit is reviewed under, for walls, flat and vaulted ceilings, slab edges and windows, and every house picks at least one additional energy measure from its list. On a steel frame, the wall assembly as a whole must perform, not just the insulation in the cavity.

Plan the next phase now

Many 30x40 owners add a garage, a porch or a second storey later. Place the mudroom and a future doorway on the wall where the garage would go, size the frame and foundation for a future upper floor if you might add one, and keep the septic reserve area clear of where the addition would sit.

Size and the rural second-home rule

At 1,200 square feet, a 30x40 is a primary home, not a rural ADU

ORS 215.495 lets a county allow one accessory dwelling unit on a lot or parcel of at least two acres in an area zoned for rural residential use, where one single-unit dwelling already stands. One of its conditions is that the unit include no more than 900 square feet of usable floor area. A 30x40 laid out as living space is 1,200 square feet, so as a second home beside an existing house it is over that cap. As the main house on its own parcel, it faces no such limit. If a second dwelling is the goal, a 30x30 footprint, or a 30x40 shell with part of it kept as a garage or shop, is where to start the conversation with the county planning office.

How people actually split 1,200 sq ft

Three common ways to divide this footprint. Yours does not have to match one exactly — this is a starting point for the conversation, not a catalog.

Two bed, two bath

1,200 sq ft living / primary suite and guest room at opposite ends

A split plan with the primary suite at one end, a guest bedroom and bath at the other, and an open kitchen and living room between, under a vaulted ceiling. The laundry sits in a mudroom at the side entry.

Three compact bedrooms

1,200 sq ft living / 3 bed, 2 bath

Two small bedrooms share a bath at one end; the primary bedroom and its bath sit at the other. The kitchen runs along one long wall to keep the living room open.

30x40 with a garage bay

900 sq ft living / 300 sq ft garage bay (30' x 10')

A one-bedroom house with a single garage or equipment bay at one end, separated by the garage wall. At 900 square feet of living space it is closer to the size a rural accessory dwelling unit may be, if the county allows one and counts the floor area that way.

Ways to build this size

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

Barndominium Kits

Barndominium kits and shell kits for Oregon land, sized to the snow, wind and seismic values the state's design hub gives for your exact site.

Pole Barn Homes

Pole barn homes and pole barn home kits for Oregon land, built as dwellings under the state residential code, not as farm buildings.

Custom Plans

Custom barndominium plans drawn for Oregon's residential code, your site's snow and seismic values, and the energy chapter a steel shell must meet.

Metal Homes

Metal building homes in Oregon, finished as real houses: insulated to the state energy chapter, detailed for wet winters, and hardened for wildfire.

30x40 Barndominium: common questions

6 questions worth settling before this plan is drawn. If yours is not on the list, put it in the survey.

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How many bedrooms fit in a 30x40 barndominium?

Two bedrooms and two baths fit comfortably; three bedrooms fit with compact rooms. Adding a partial second storey or a mezzanine gives more room on the same footprint.

Can a 30x40 be a second home on my rural property?

Not at full size as living space. ORS 215.495 caps a rural accessory dwelling unit at 900 square feet of usable floor area, among other conditions, and only where the county allows one. A 30x40 laid out entirely as living space is 1,200 square feet.

What septic system does a 30x40 need?

The same minimum tank as any Oregon house with four or fewer bedrooms: 1,000 gallons under OAR 340-071. The drainfield is sized from the design flow and the site evaluation.

How much insulation does a 30x40 steel house need?

The ORSC energy chapter sets the insulation and window values for the edition your permit is reviewed under: walls, ceilings, slab edges and windows each have their own entry, and every house adds at least one additional energy measure. A steel wall conducts heat through its frame, so plan continuous insulation or a thermal break and confirm the assembly at plan review.

Can I add a second storey to a 30x40 later?

Only if the frame and foundation were designed for it. If you might, size them for the future load now; retrofitting a frame for a second floor costs more than planning it.

Is a 30x40 big enough for a family?

For a small family, yes, with two or three bedrooms. For more bedrooms or a home office, a 30x50 or a 40x50 gives the extra room without changing the building much.

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

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Sources

Code figures on this page are from the 2023 Oregon Residential Specialty Code. The Building Codes Division anticipates a 2026 edition from October 1, 2026, with a six-month phase-in; the edition your permit is reviewed under governs.

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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.

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