800 Sq Ft ADU Floor Plans: A 2-Bed Layout, Room by Room

Good 800 sq ft ADU floor plans (what is an ADU?) fit two bedrooms, one full bath, a laundry closet and an open kitchen, dining and living area into a simple rectangle, usually 40 × 20 ft or close to it. That is enough for a couple, a small family or a parent moving in (for an attached option, see in-law suite additions), as long as the hall stays short and the bath sits between the bedrooms and the living space. Below is one such plan measured room by room, then the reasons 800 ft² is such a common target and the ways to rearrange it.

Why 800 sq ft keeps coming up

The number is not arbitrary. California made 800 ft² a protected size: state law says a city cannot use lot coverage, floor area ratio, open-space rules or front setbacks to block a new ADU of up to 800 ft² with 4 ft side and rear setbacks, and a detached unit of that size may generally be at least 16 ft tall (Gov. Code 66314 and 66321, and the statewide exemption ADU in 66323). Above 800 ft² a city may apply its ordinary lot rules. The details, and the 850 and 1,000 ft² caps that sit above it, are in California ADU size limits.

Elsewhere, 800 ft² shows up mostly in local codes rather than state law. Many city and county ordinances cap a detached ADU at "800 ft² or a percentage of the main house, whichever is less". The newer state laws tend to set a higher floor: Washington's HB 1337 requires cities to allow ADUs of at least 1,000 ft², and Arizona's 2024 HB 2720 requires cities over 75,000 people to allow at least 1,000 ft² or 75% of the house, whichever is less. In those states an 800 ft² plan fits under the size rule with room to spare. The ADU laws by state post compares them.

An 800 sq ft ADU floor plan, measured

FloorGen's 800 sq ft 2-bed ADU template is a 40 × 20 ft rectangle to the outside faces of its walls. The two bedrooms take the west end. A 4 ft hall runs between them and the bath, with a stacked laundry closet beside it. The kitchen, dining area and living room share the east end, and the front door opens into the living room.

Read the totals carefully. About 100 ft² of the 800 goes to walls: the exterior walls are drawn about 6½ in thick and the partitions about 4½ in. Every plan this size loses a similar share, so be wary of a listing that claims 800 ft² of "living space".

What makes this layout work

• One wet wall. The bath, laundry and kitchen sit side by side in the middle of the plan, so the supply and drain runs stay short.
• The hall is the only corridor. At 48.1 ft² it is about 7% of the net area. Plans that wrap a hall around a bath often spend twice that.
• Bedrooms on the quiet end. Both bedrooms are behind the bath and laundry, away from the front door and the TV wall.
• Open public space. Kitchen, dining and living add up to 376.6 ft², which reads as one large room even though the plan is only 20 ft deep.

Five ways to rearrange 800 sq ft

The same area can take very different shapes. The right one depends on your lot, the setbacks and who will live there. For other two-bedroom shapes, see 2 bedroom house plans.

Two notes on the variants. A two-storey ADU gives up floor area on both levels to the stair, roughly 35 to 45 ft² per floor for a straight run (a rule of thumb), and California's 16 ft height floor may not cover it; check your local height limit. And the 1-bed versions are not just smaller 2-beds: with only one bedroom, consider a larger, curbless shower and 36 in doors, which matter more than a second bedroom for someone aging in place.

Code items for an 800 sq ft ADU

A detached ADU is a dwelling, so the full residential code applies. Section numbers here are from the 2021 IRC, with 2024 numbers where the edition renumbered them. Your state or city may adopt a different edition with amendments.

• Room size: habitable rooms other than kitchens need at least 70 ft² and 7 ft in every direction (2021 IRC R304 / 2024 IRC R312). Both bedrooms here pass, the smaller one at 93.2 ft².
• Ceiling height: at least 7 ft in habitable rooms and halls, 6 ft 8 in in bathrooms and laundry rooms (2021 IRC R305.1).
• Escape openings: each bedroom needs a window or door with at least 5.7 ft² of net clear opening, 24 in high and 20 in wide, sill no more than 44 in off the floor (2021 IRC R310 / 2024 IRC R319).
• Alarms: smoke alarms in each bedroom and outside the sleeping area (2021 IRC R314 / 2024 IRC R310), and CO alarms if there is a gas appliance (2021 IRC R315 / 2024 IRC R311).

Utilities, fire access and separation from the main house are set locally. Some utilities let an ADU share the main house's meter, others require a new one, which changes where the panel goes in the plan.

Adapt the plan to your lot

Open the template, drag the exterior walls to your buildable area, and the room areas update as you go. FloorGen's IRC profile flags a habitable room that drops under 70 ft² or 7 ft across, a ceiling under the R305 minimums, and a bedroom without an escape opening of the R310 size, so you see the problem while you are still moving walls. It does not know your zoning, so check setbacks and size caps with your planning department.

If 800 ft² is more than your yard allows, a converted two-car garage gives you a studio of about 400 ft²; see garage conversion floor plans.