Casita & ADU Pricing · Arizona
What a Casita or ADU Costs in Arizona
Real ranges from a licensed West Valley builder, taken off our own completed projects, plus a straight answer on what Arizona's ADU law does and doesn't do for your lot.
$150,000 – $1,000,000+
We start stand-alone casita and ADU projects at $150,000.
A detached dwelling needs a foundation, framing, a roof, a full bath, kitchen or kitchenette, HVAC, and its own utility connections. Those costs arrive whether the building is 400 square feet or 1,000, which is why the floor sits where it does.
A casita or ADU in Arizona costs $150,000 to $1,000,000+ in Matson Signature Builders 2026 pricing. A garage or interior conversion runs $150,000 to $250,000 because the slab and roof already exist, while a detached new build needs its own foundation, utilities and kitchen and typically starts around $250,000.
Why we published this
A real number, before you spend three weeks finding out.
Arizona casita pricing is easier to find than RV garage pricing, but most of what's published is either a per-square-foot figure that ignores site costs, or a range so wide it tells you nothing.
So here is ours, taken off finished projects. $150,000 is where our stand-alone casita work starts, and that number happens to match the published minimum of the most established design-build firm in the Phoenix metro. It is not a low-ball to get you on the phone.
What actually decides your number is on this page: whether it's a conversion or new construction, whether it has a full kitchen, and how far your utilities have to travel.
What moves the number
What actually drives the price
Six things decide where a casita lands. The first two account for most of the spread.
Conversion or new build
Converting an existing garage or shop reuses a slab, walls and a roof that are already there, usually the least expensive path to a legal dwelling. A new detached build starts from bare ground and prices accordingly.
Full kitchen or kitchenette
A full kitchen brings cabinetry, counters, appliances, venting and heavier plumbing and electrical. A kitchenette does much less of all of it. This single decision moves the number more than almost anything else inside the walls.
How far the utilities run
Water, sewer, power and sometimes gas have to reach a detached building. On a deep Valley lot that can be a long trench, and some cities require separate metering. It's real money spent before anything is visible.
Size and layout
Arizona's ADU law caps size relative to your main house, and within that cap a studio and a two-bedroom are different builds. More walls, more plumbing fixtures and more roof all carry cost.
Matching the main house
We match stucco, roofline, paint and finishes so the casita reads as part of the property rather than an afterthought. It's the detail that protects your home's value, and it costs more than not bothering.
Your lot
Slope, soil, drainage, setbacks and equipment access all affect what the foundation and site work cost before framing starts.
Placing your project
Where your build lands in that range
Every lot is different. Here is how casita projects actually move through that range.
A conversion or attached suite
Reusing an existing garage or building attached to the house, with a kitchenette, a full bath and its own entry. The fastest path to a legal, comfortable second dwelling.
A detached casita, fully finished
New construction, detached, with a full kitchen and bath, its own HVAC and utilities, finished to match the main house. This is the majority of what we build.
A guest house in its own right
Larger, multi-room, high-finish, sometimes with covered parking or a garage attached. At this level it's a small custom home, and it's priced and permitted like one.
Bringing it down
What lowers the cost
If the number is higher than you hoped, these are the honest levers.
Convert what you have
An existing garage or shop already has a slab, walls and a roof. It is almost always the least expensive route to a legal dwelling.
Kitchenette instead of full kitchen
If it's for family rather than a long-term tenant, a kitchenette often does the job for meaningfully less.
Build attached
Sharing a wall with the house shortens utility runs and can simplify the foundation.
Site it close to the house
The shorter the trench for water, sewer and power, the lower the cost before anything is visible.
Right-size it
A well-planned smaller footprint beats a larger one with wasted circulation, and it stays comfortably inside the size cap.
Match the finish to the use
A mother-in-law suite and a rental unit are not the same build. Spend where it will actually be noticed.
Arizona ADU law
What the state law does, and where it stops
Arizona's HB 2720 took effect on January 1, 2025. It requires municipalities with 75,000 or more residents to allow at least one attached and one detached accessory dwelling unit on single-family lots, sized up to 75% of the main home's floor area or 1,000 square feet, whichever is less.
That threshold matters, and it is where most articles stop. Several Valley communities sit under 75,000 residents and are therefore not covered by that requirement, which does not mean a casita is impossible there, only that it is governed by local zoning rather than the state mandate.
Separately, your HOA is not bound by any of it. State law does not override CC&Rs. We confirm your specific city's current rules and your HOA's requirements before design starts, rather than telling you what the law says in general and letting you find out the rest at plan review.
Questions
Casita & ADU Cost, Questions Answered
What does a casita or ADU cost in Arizona?
Our casita and ADU projects run $150,000 to over $1,000,000. A garage conversion or attached suite sits near the bottom. A large, high-finish detached guest house sits at the top. We start stand-alone casita projects at $150,000.
Is it cheaper to convert a garage than build new?
Almost always, yes. A conversion reuses a slab, walls and roof that already exist. The trade-off is that you give up the garage, and the finished space is limited to the footprint you already have.
Does my city allow an ADU?
Arizona's HB 2720 requires cities of 75,000 or more residents to permit ADUs on single-family lots, effective January 1, 2025. Smaller communities are governed by their own zoning instead. We confirm your specific city's current rules before design starts.
Will my HOA allow it?
That's a separate question, and state law does not override your CC&Rs. Some HOAs permit casitas readily when the design matches the main house. Others restrict them. We check before anything is drawn.
How big can it be?
Under the state law, up to 75% of your main home's floor area or 1,000 square feet, whichever is less. Local rules may differ, so we confirm against your specific property.
Does it need its own utility meters?
It depends on your city and on how the unit will be used. Some jurisdictions require separate metering and some don't. It's one of the first things we check, because it affects both cost and schedule.
Can I rent it out?
Long-term rental rights are protected under the state law in covered cities. Short-term rules vary by jurisdiction and can change. We'll tell you what your city currently allows, and we won't put a rental income projection on this page, because it depends on your lot and how you'd market it, and a number that doesn't hold up is worse than no number.
How long does a casita take to build?
Design and engineering come first, then permitting, then construction. Timelines vary meaningfully by city. We'll give you a realistic schedule for your jurisdiction before you sign anything.
Find out what your casita would cost.
Tell us your lot and what you need the space to do. We'll give you an honest range, and tell you plainly whether a conversion or a new build is the smarter money.
A note on these numbers. They come from casita and ADU projects Matson Signature Builders has actually built across the Valley, at 2026 material and labor costs. Every lot, city and HOA is different, and the only honest price for your casita is one that comes from a defined scope and a site visit. Statements about Arizona ADU law are general and current as of August 2026. We confirm your specific city's rules before design begins. Licensed Arizona contractor, ROC 336562. Last updated August 2026. We review this page every year.
Related reading
Last updated August 2026 · Matson Signature Builders · Licensed Arizona contractor ROC 336562