30' x 40' · 1,200 sq ft footprint

30x40 Barndominium Floor Plans in California

A 30 by 40 foot barndominium gives 1,200 square feet on one floor: enough for a comfortable two-bedroom home, a tight three-bedroom one, or a small apartment beside a shop bay. It is the size many California owners choose for a first building on raw land, a retirement home, or a second home on a parcel that already has a house. A 30-foot span is easy for either a steel rigid frame or pole barn trusses, and the whole building fits on a modest pad, which helps on a sloping foothill lot or where the septic field and the fire clearances leave little flat ground.

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What actually changes at this size

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

A second home on an existing parcel

California's ADU law requires qualifying accessory dwelling units to be approved ministerially, without a hearing, under the city's or county's objective standards, and a detached ADU of up to 1,200 square feet beside an unsprinklered main house is one of the exceptions to the residential sprinkler requirement. Ask the planning department which zone your parcel is in and what size a second home may be before settling on 30x40, because a slightly smaller footprint may fit a limit that 1,200 square feet does not.

A small roof, a full solar array

One slope of a 30x40 gable roof is about 40 feet by 16 feet, enough for a solar array sized for a small, efficient home if nothing else is on it. Keep plumbing vents, fans and skylights on the other slope. Under the 2025 Energy Code, a new single-family home generally needs a solar PV system sized by a state formula; small or shaded roofs can be exempt, and a qualifying battery can cut the required size by 25 percent.

A small house in a hot place

A compact building has less wall and roof for the sun to heat, which is an advantage in the Central Valley and the high desert. Run the long walls east to west, keep west-facing glass small, and add a porch on the west or south side. A single mini-split system or a small ducted heat pump can condition the whole house.

Wildfire detailing on a compact building

In a Fire Hazard Severity Zone, homes are built to the California Wildland-Urban Interface Code (Part 7 of Title 24), which covers Class A roofs, eaves, vents, exterior walls, windows, doors and decks; your building department confirms the specific assemblies. On a 30x40 the list of details is short: enclosed eaves, ember-resistant vents, a noncombustible gutter guard, and nothing combustible stored against the walls. Drawn in at the start, they add little to the build.

Every foot counts

At 1,200 square feet, the fixed rooms set the plan

In a 30x40, the kitchen, one or two bathrooms, the laundry and a mechanical closet for the water heater and air handler take up a large share of the floor, and they are the same size whether the house is 1,200 or 2,400 square feet. Grouping them along one interior wall, with the kitchen, bath and laundry back to back, keeps pipe runs short and leaves the rest of the floor open for living and sleeping. A vaulted ceiling over the open living area makes the house feel larger than its footprint, and a porch outside adds usable space without adding to the heated floor.

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 bedrooms, open living

1,200 sq ft / 2 bed, 2 bath

Two bedrooms at one end, each with its own bath, and an open kitchen and living room under a vaulted ceiling at the other. The laundry and mechanical closet sit between the bathrooms. It suits a couple, a retirement home, or a second home for family.

Tight three-bedroom

1,200 sq ft / 3 bed, 2 bath

Three smaller bedrooms along one long wall, two baths, and a combined kitchen, dining and living area. It works as a starter family home on a budget, with a porch or a patio doing the job of a family room for most of the year.

Apartment beside a shop bay

600 sq ft living / 600 sq ft shop or garage

A one-bedroom apartment in half of the building and a shop or two-car garage in the other half, with a fire-rated wall between them. Common as the first building on raw land: somewhere to live and store tools while the main house is planned.

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 for sale in California: steel and pole barn shell packages, kit vs modular vs manufactured explained, and what California adds.

Pole Barn Homes

Pole barn homes in California: wood-framed barndominiums and pole barn home kits, drawn for your county's plan check and built on your land.

Custom Plans

Custom barndominium plans in California: a floor plan drawn around your land and your shop, and a plan set ready for your building department.

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 square feet is a 30x40 barndominium?

1,200 square feet on the ground floor, measured to the outside of the frame. A porch adds covered outdoor space outside that figure; a loft over part of it adds floor area.

How many bedrooms fit in a 30x40 barndominium?

Two bedrooms comfortably, three if the bedrooms are compact. With a loft, a third sleeping space can go upstairs while the ground floor keeps two larger bedrooms.

Can a 30x40 barndominium be a second home or ADU?

It can be, if the parcel already has a main house and the city or county's objective standards allow a unit of that size. California's ADU law requires qualifying accessory dwelling units to be approved ministerially, without a hearing, and an ADU cannot be sold separately from the main house. Check the zone and the size limit for your parcel with the city or county planning department before settling on the footprint.

Is a 30x40 barndominium sold as a kit?

Yes, 30x40 is a common kit size. The kit supplies the frame, roof and wall panels; the foundation, interior, utilities and the structural drawings prepared for your site are separate. In California the frame is checked against the seismic, wind and snow values for your location, and a steel frame needs structural plans stamped by a licensed engineer or architect.

Can I add a loft to a 30x40?

Yes, if the eave height is tall enough. A 14- to 16-foot eave leaves room for a loft over the bedrooms or the bath and laundry, reached by a stair along the end wall. Plan it on the first drawings so the frame and the sprinkler layout account for it.

Is a 30x40 big enough for a family?

For a small family, yes, especially with a porch and a loft. For a family of four or five, most owners find 1,600 square feet or more easier to live with; a 30 by 50 or 30 by 60 building keeps the same span and simply adds bays.

Keep reading

The pages that answer the next question this one raises.

40x60 barndominium floor plans

Double the floor area, for three or four bedrooms or a house with a full shop.

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Small barndominium floor plans

Plans under 1,200 square feet, and the second-home questions that come with them.

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

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Sources

Code references on this page are to the 2025 California Building Standards Code (Title 24 of the California Code of Regulations), in effect since January 1, 2026. Cities and counties can keep local amendments adopted before October 2025 and can add wildfire home-hardening rules, but a state moratorium blocks most new local code changes for homes until June 2031. Snow load, wind speed, frost depth and seismic design category are set for your site by the local building department.

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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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