1 bedroom ADU floor plans: sizes, layouts and costs

How big is a 1 bedroom ADU?

Plans that a city or county has already checked are the most honest guide to what a one-bedroom needs. Across the public plan sets in San Diego County, a one-bedroom starts around 400 sq ft and tops out where the bedroom stops being the only extra room.

Sources: La Mesa's pre-approved plans, Escondido's PAADU plans, the County of San Diego's plan list and Snap ADU's one-bedroom catalog, which lists 26 plans from 400 to 999 sq ft. The County plans at 800 and 1,000 sq ft show that a single bedroom can go much bigger, but most of the extra space becomes living room and storage. If you want a quick look at every size from studio to three bedrooms, start with our ADU floor plans overview; this guide goes deeper on the one-bedroom.

Since January 1, 2026, state ADU size limits are measured as interior livable space, so ask how a plan's square footage was counted before you compare it with your city's limit.

What fits from 450 to 750 sq ft

The code sets the floor for any bedroom. Under the 2025 California Residential Code, a habitable room needs at least 70 sq ft and 7 feet in every direction, ceilings of at least 7 feet, and every sleeping room needs an emergency escape window. Past that, the size of a one-bedroom decides how much kitchen, storage and laundry you get. Snap ADU's published plan pages make a useful ladder, because each one describes its rooms.

About 450 sq ft: the compact 1 bedroom ADU

Snap ADU's 425 sq ft plan, 31 by 13 feet, puts an open living room and kitchen at the front door, then a hall to a full bathroom and a bedroom that fits a queen bed. It has no laundry. That's the typical trade at this size: a real bedroom with a door, but no room for a washer. Our small ADU guide covers studios and 400 sq ft units if you're weighing a studio instead.

About 550 to 600 sq ft: room for laundry

Around 550 to 600 sq ft, laundry moves in. Snap ADU's 560 sq ft L-shaped plan has an open great room, a bedroom that fits a queen or king bed with its own bathroom, and an in-unit laundry area. The County's 600 sq ft Plan F fits a living room, kitchen, bedroom, bathroom and a separate laundry room.

About 700 to 750 sq ft: the roomy one-bedroom

At 700 sq ft and up, the extra space goes to storage and a bigger bath. Snap ADU's 696 sq ft square plan has two bedroom closets, a double-sink vanity, a side-by-side washer and dryer and a kitchen island. Its 749 sq ft plan adds a walk-in closet, a pantry, a hall closet and a bedroom large enough to double as an office. Keeping that plan at 749 sq ft rather than 751 is deliberate; see the fee lines below.

800 sq ft 1 bedroom ADU floor plans

The County's free 800 sq ft Plan E is a one-bedroom, one-bath unit. At this size you're paying for space that most one-bedroom renters won't value as much as a second bedroom, so compare it against a two-bedroom layout of the same size in our 2 bedroom ADU floor plans guide.

1 bedroom ADU layouts: long, L-shaped and square

Floor area is only half the question. The shape of the footprint decides whether the unit fits your yard. Builders group one-bedroom plans into three shapes, and Snap ADU's catalog has examples of each:

• Long plans hug a property line. In the City of San Diego, an ADU 16 feet tall or less needs no interior side or rear setback, except 4 feet in high and very high fire hazard zones. A 13-foot-wide plan can slip along a fence where a square one can't. Elsewhere, state law guarantees you can build with 4-foot side and rear setbacks.
• L-shapes separate sleeping from living. The bend puts a wall and a corner between the bedroom and the kitchen, which helps if two people keep different hours.
• Square plans waste the least. Less exterior wall per square foot usually means less framing, siding and roof edge. This is a rule of thumb, not a published price difference.
• Short on yard? Go up. Snap ADU's catalog also includes two-story one-bedroom plans. Our two-story ADU guide covers the height and setback rules that come with a second floor.

Fee lines at 500 and 750 sq ft

Two size lines matter most for a one-bedroom, and good plans are drawn to land just under them.

• Under 500 sq ft. ADUs under 500 sq ft owe no school fees under state law. Above that, San Diego Unified charges $5.38 per sq ft; other school districts set their own rates.
• 750 sq ft. A city can't charge impact fees on an ADU of 750 sq ft or less, and above that the fee must be proportional to the main house. The City of San Diego goes further and exempts the first two ADUs on a lot regardless of size.
• From 2027. A bill signed in September 2026, SB 1117, limits impact fees to the area above 750 sq ft starting January 1, 2027.

The jump in Snap ADU's fee table between 499 and 749 sq ft is about $14,400. Those are a builder's estimates, not official city figures, but they show why so many one-bedroom plans stop at 499.

1 bedroom ADU cost

Builder plan prices cover the building and its finishes. They leave out design, permits, fees and site work, which can add a lot.

Sources: Snap ADU plan pages. Each says the project “will also require plans, permits, sitework and other work that is dependent on your lot.” For all-in numbers, Snap ADU's published San Diego prices (March 2026) put a detached 500 sq ft ADU at about $300,000 and a 750 sq ft one at about $350,000, including design, permit management and about $35,000 of site work on a level lot. Lars Remodel's October 2026 estimate puts detached ADUs at $250,000 to $450,000 or more.

Run your own numbers with our ADU cost calculator, or read what an ADU costs in San Diego for site costs like trenching, meters and slopes.

What a 1 bedroom ADU rents for

The 2026 fair market rent for a one-bedroom in San Diego County is $2,459 a month. That's HUD's estimate for a modest unit, not a new ADU, so treat it as a floor. Our ADU rental income guide covers the rest of the math.

An accessible one-bedroom

A one-bedroom is the most common ADU for a parent, which makes it the best place to plan for a walker or wheelchair. Accessibility is cheap to draw and expensive to retrofit. Designers often borrow dimensions from the federal ADA Accessibility Standards. They aren't required for a private ADU, but they're a tested benchmark.

These dimensions push a one-bedroom toward the upper end of the range. A 36-inch hall and a 60-inch turning circle in the bathroom are hard to fit in a 425 sq ft long plan, and much easier in a 600 to 750 sq ft square or L-shaped one. Stay on one floor, and block the bathroom walls for grab bars during framing. Our ADU for seniors guide covers the rest.

Free 1 bedroom ADU plans

Several San Diego County governments publish one-bedroom plans you can use for free or close to it.

• County of San Diego, Plans E and F. 800 and 600 sq ft, one bed and one bath, in PDF and CAD. They're about 85% complete; you add the site plan, stormwater forms, energy calculations and truss design.
• City of Escondido, Plan 1. 484 sq ft, studio or one-bedroom. For new single-story detached ADUs only, and you can change select features like windows and doors, but not the size or layout.
• City of La Mesa, Plans B and C. 400 and 499 sq ft one-bedrooms, both under the school-fee line.
• City of Encinitas. Permit-ready plans from a studio to three bedrooms.

A free plan still needs a builder. Compare verified ADU builders in San Diego, see our best ADU builders in San Diego list, and check a contractor's license before you sign. Our guide on how to hire an ADU contractor covers deposits and contracts.

Common questions