How Much Does a 2 Bedroom ADU Cost?

A two bedroom ADU runs $96,075–$375,000 all in, nationally, at a standard finish. A detached two bedroom, which is what most of these projects are, prices $210,000 at 700 sq ft and $300,000 at 1,000 sq ft.

The assumption behind those numbers, stated plainly: I price a two bedroom ADU at 700 to 1000 square feet. That is the band our Nevada and Washington cost pages already use for two bedroom layouts, and 1,000 is where California's own size protection for a multi-bedroom unit tops out.

Here is what makes this page different from the rest of the silo. That 700 to 1000 band straddles California's 750 square foot fee threshold. A 700 square foot two bedroom pays no impact fees. A 1,000 square foot one does. Same bedroom count, different bill.

2 bedroom ADU cost by type

Every build type across the 700 to 1000 square foot band, at a standard finish, nationally. The junior ADU row is dead here and stays on the table only to say so.

Detached against attached is the live comparison at $255,000 and $202,300. Sharing a wall is worth $52,700 at this size, though it costs you the ability to treat the unit as a genuinely separate home.

National, standard finish, before any city adjustment. Typical all-in is the point estimate; the range is the engine's residual spread for site conditions, utilities and contractor.

What Changes at Two Bedrooms

Your bedroom count buys you a legal size floor. Government Code section 66321(b)(2) prohibits a California city from setting a maximum ADU size below 850 square feet of interior livable space, or below 1,000 square feet for an ADU that provides more than one bedroom. That second clause exists for exactly this page. A two bedroom design is the thing that unlocks the 1,000 square foot protection, and a studio at the same square footage does not get it.

And it can cost you the fee exemption. Section 66311.5(c)(1) exempts an ADU of 750 square feet or less from every impact fee. Subdivision (c)(2) charges anything above that proportionately against the primary dwelling's square footage. So the 700 to 1000 band this page prices has the threshold running straight through the middle of it, at 750.

What that is worth is a local number, and Campbell publishes one clean enough to use. Campbell's park in-lieu fee is $0 under 750 sq ft and jumps to $9,328 at 750 sq ft or larger. That single line is the difference between roughly $7,700 and $17,100 in combined city fees, so it is a design decision rather than a surprise bill. City of Campbell FY2026-27 Master Fee Schedule, effective July 1, 2026. A two bedroom laid out at 750 square feet instead of 800 is the same unit with a tighter hallway, and in that city it is a five figure decision.

A tight two bedroom is a real design, not a compromise. 750 square feet takes two bedrooms and a bath if the plan is disciplined about circulation. I would rather build that than a 900 square foot two bedroom with a corridor, and in California the fee line makes the tighter plan cheaper twice over. That said, if the unit is housing family long term, build the space they need and pay the fee. Nobody has ever thanked me for a bedroom you have to walk sideways in.

The junior ADU is not an option and has not been since 500 square feet. Section 66313 caps it, and no two bedroom layout fits under that cap. The JADU guide explains the trade if you are still weighing it.

If you want to see what this size actually looks like laid out, we have 11 original 2 bedroom floor plans drawn to scale with room dimensions, each with a walkthrough of what works and what to watch.

2 bedroom ADU cost by city

A two bedroom ADU priced through every city index we maintain, at the middle of the 700 to 1000 square foot band. The range column spans the whole band and every eligible type.

Standard finish. The cost index is that city's published average against our national reference, so these columns move whenever a city cost page does. Full range spans every eligible build type at this size.

What finish level does to it

Finish level moves a two bedroom budget by $107,100, against $90,000 for the entire 700 to 1000 square foot spread. The finish decision is the bigger one, and it is the one people make last.

National point estimates at 850 sq ft. The junior ADU column, where it appears, is priced at its 500 sq ft statutory cap rather than at this page's size.

A worked budget

Where $255,000 goes on a 850 sq ft detached two bedroom at a standard finish, nationally.

Detached ADU, 850 sq ft, standard finish, national. $300 per sq ft all in, with a planning range of $191,250–$318,750.

Frequently asked questions

How Much Does a 2 Bedroom ADU Cost?

Nationally, $96,075–$375,000 all in at a standard finish, priced across 700 to 1000 square feet and every eligible build type. A detached two bedroom runs $210,000 to $300,000 depending on size, and in California the same unit at the middle of the band prices near $464,100.

How Many Square Feet Is a 2 Bedroom ADU?

Typically 700 to 1000 square feet, which is the assumption behind every number on this page. Below 700 the second bedroom starts eating the living space, and 1,000 is where California's guaranteed maximum for a multi-bedroom ADU sits, so most two bedroom designs land inside that band by default.

Do I Pay Impact Fees on a 2 Bedroom ADU in California?

It depends where in the band you land. Government Code section 66311.5(c)(1) exempts any ADU of 750 square feet or less of interior livable space, so a compact two bedroom at 750 pays nothing. Above that, subdivision (c)(2) charges fees proportionately in relation to the primary dwelling's square footage, so a 1,000 square foot two bedroom next to a 2,000 square foot house pays about half.

Can My City Limit Me to One Bedroom?

Not by imposing a size cap that makes two bedrooms impossible. Government Code section 66321(b)(2) blocks a local maximum below 1,000 square feet for an ADU providing more than one bedroom, which is the state's way of protecting family-sized units. Other standards like height, lot coverage and setbacks still apply and can constrain the design in practice.

Is a 2 Bedroom ADU Worth the Extra Cost?

It depends on the rent gap in your market. The second bedroom costs roughly $90,000 of construction across this band nationally, and in California it can also move you past the 750 square foot fee threshold. If the unit is housing family, build it. If it is a rental, compare local one and two bedroom rents and check whether the difference services that extra cost.

If I were building a two bedroom in California and the city charged real impact fees, I would ask the designer for a 750 square foot plan before anything else and see whether it works. Often it does.

If it does not, build the size the household needs and stop optimising. Then compare it honestly against a one bedroom, because the second bedroom has to earn its $90,000 in rent, and in some markets it does not.