Casitas · conversions · in-law suites
ADU & Casita Builder in Gilbert, AZ
A casita in the backyard used to be a zoning fight. Today, across most of the Phoenix Valley, it's a permit application — and for a lot of homeowners, it's the single most useful square footage they'll ever add. Masizo Development designs and builds accessory dwelling units across Gilbert, Mesa, Chandler, Queen Creek, San Tan Valley, Tempe, Scottsdale, Phoenix, Fountain Hills, and Paradise Valley: detached casitas and guest houses from the slab up, garage conversions that turn parked-car space into living space, and attached in-law suites that give family a place of their own. We're a licensed Arizona general contractor (AZ ROC #336058) with 28 years of building in the Valley, and we handle the whole project — design coordination, permits, zoning, construction, and every city inspection — under one contract.
- 28 years · since 1998
- AZ ROC #336058
- AZ ROC #347030
- CA LIC #1107781
- IICRC certified
- Insured
- BBB A+ accredited
What counts
What Counts as an ADU
"Accessory dwelling unit" is the planning department's name for a second, self-contained living space on a single-family lot. Everything Arizonans actually call these projects falls under it:
- Casitas and guest houses — detached structures, usually in the backyard, with their own entrance, bathroom, and typically a kitchenette or full kitchen.
- Garage conversions — an existing attached or detached garage rebuilt as finished living space.
- In-law suites — attached additions or converted interior space arranged so a parent or adult child lives connected to the household but behind their own door.
The label matters less than the function: a space someone can genuinely live in, built legally, permitted properly, and tied into utilities correctly. That last part is where an experienced general contractor earns their keep.
The law
Arizona's ADU Law, in Plain Terms
Arizona changed the rules in homeowners' favor. A statewide law — HB 2720 — now requires many of the state's larger cities to allow ADUs on lots zoned for single-family homes, and the cities it covers include most of the East Valley and Phoenix-metro communities we work in every week. In practice, that means the question for most of our clients is no longer whether they're allowed to build, but what makes sense on their particular lot.
We've kept the statute detail out of this page on purpose, because the specifics — how many units a lot can hold, size allowances, setback and parking rules, what cities can and can't require, and how rentals are treated — deserve a careful, sourced explanation. That's exactly what our Arizona ADU law guide provides, city by city. Read it before your consultation if you like homework; skip it if you'd rather we walk you through what applies to your address in person. Either way, two things always remain lot-specific: your parcel's dimensions and utilities, and your HOA's covenants. We review both at the free consultation, before you've spent a dollar.
Ground-up casitas
Casitas and Guest Houses, Built From the Ground Up
A detached casita is a complete small building: foundation, framing, roof, electrical, plumbing, HVAC, insulation, drywall, and finishes. We build it the same way we build a custom home, because structurally that's what it is — just scaled down. Our crew handles the site work and slab, frames and dries in the structure, runs the systems, and finishes the interior to match the quality of your main house, from flooring to fixtures.
Ground-up construction gives you the most freedom: you choose the footprint, the layout, the ceiling height, where the windows face, and whether the unit gets a full kitchen or a kitchenette. It's the right path when privacy matters — for a long-term tenant, or for family members who want genuinely separate households sharing one property.
Garage conversions
Garage Conversions: The Faster, Leaner Path
If your garage sits full of boxes instead of cars, you may already own the shell of your ADU. A conversion starts with the slab, walls, and roof in place, which typically makes it the quickest and most budget-conscious way to add living space. Our scope on a conversion usually includes insulating walls and ceiling to livable standards, replacing the garage door with a framed, finished wall and proper entry, extending electrical and HVAC, adding plumbing where the layout calls for a bathroom or kitchenette, and finishing the interior so that nothing about the room says "this used to be a garage."
Conversions still require permits — this is a change of use, and the city will inspect it like any other habitable space. We coordinate that permitting just as we do on ground-up builds, so the finished room is legal, insurable, and counted when it matters.
In-law suites
In-Law Suites and Multigenerational Living
A large share of the ADU work we do isn't about rent at all. It's about an aging parent who shouldn't be across town, or an adult child saving for their own place, or simply a household that works better with one more private door in it. Attached in-law suites — built as an addition or converted from existing space — keep family close while preserving the privacy both sides need: a separate entrance, a private bathroom, and ideally a small kitchen setup so nobody is negotiating over one coffee maker.
If you're weighing an attached suite against simply enlarging the house, our room additions page covers that comparison — the short version is that an ADU is a self-contained dwelling, while an addition grows the main home. We build both, so our advice at the consultation isn't steering you toward anything; it's matching the structure to how your family actually plans to use it.
Rental income
The Rental-Income Question
Long-term rental is one of the most common reasons Valley homeowners build an ADU, and it's a legitimate one: a well-built casita is housing someone will pay for, on land you already own. We won't quote you rental figures — that's your local market and your decision, not a construction company's promise — but we will build the unit so it works as a rental: durable finishes, sensible utility arrangements, sound separation from the main house, and a layout a tenant actually wants to live in. The rental rules under Arizona's ADU law are covered properly in the guide.
Cost drivers
What Shapes the Cost of an ADU
Every lot is different, so we price from a site visit rather than a brochure. The variables that move the number most are the ones worth knowing up front: ground-up construction versus conversion of existing structure; the unit's size and whether it includes a full kitchen; how far electrical, water, and sewer have to travel from your existing service to the new space, and whether your panel has capacity to spare; site access for equipment and materials; and finish level. None of these are reasons to wait — they're the agenda for the free consultation, and you'll see each one priced plainly in the written quote.
How it works
How Your ADU Gets Built
- Free lot consultation. We walk your property, evaluate where a unit can sit, review utilities, lot constraints, and HOA covenants, and talk through your goals. No cost, no obligation.
- Design, quote, and permits. We coordinate the plans, give you a clear written quote, then file the permit package and work directly with your city's planning staff until it's approved.
- Construction. Slab to finishes on ground-up builds; demo to finishes on conversions. We schedule every required city inspection and keep you updated as each phase passes.
- Final walkthrough. We walk the completed unit with you, resolve anything on the list, and hand over a space that's ready for family, guests, or a tenant.
Credentials
Licensed, Insured, and Local
Masizo Development is an Arizona licensed general contractor (AZ ROC #336058), also licensed in California (CA LIC #1107781), and carries a separate Arizona restoration license (AZ ROC #347030). We're insured, we've been building in Arizona for 28 years, and we answer our own phone — (602) 909-7630, or email office@masizodevelopment.com. You can see completed work in our portfolio and read what clients say on our reviews page.
An ADU is a small building with every complication of a big one. Build it with a contractor licensed to handle all of them. Schedule your free lot consultation — or check whether we cover your city on our service areas page.
Good to know
ADU questions, answered.
Can I build an ADU in my backyard?
In much of the Phoenix Valley, yes. Arizona passed a statewide ADU law that requires many Valley cities to allow accessory dwelling units on single-family lots, and most of the cities we serve are covered by it. Your specific lot still matters — lot dimensions, utility access, and HOA rules can all shape what you can build — which is exactly what we check during the free consultation. For the details of the law itself, read our Arizona ADU law guide.
What's the difference between a casita, a guest house, and an ADU?
Functionally, nothing. 'Accessory dwelling unit' is the legal term for a self-contained second living space on a single-family lot. In Arizona, people call them casitas, guest houses, in-law suites, or granny flats. Whether it's detached in the backyard, attached to the main house, or converted from a garage, it's the same category of project — and the same permit path.
Can I rent out my ADU?
Long-term rental of an ADU is permitted under Arizona's ADU law in the cities it covers, and rental income is one of the most common reasons our clients build. Rules around short-term rental are a different question and vary by city. We walk through what applies to your property at the consultation, and our ADU law guide covers the rental provisions in depth.
Is a garage conversion cheaper than building a detached casita?
Usually, yes — a garage conversion starts with a slab, walls, and a roof that already exist, so you're paying for insulation, systems, interior buildout, and finishes rather than a full structure from the ground up. It's also typically faster. The trade-off is you lose the garage and you're working within its existing footprint. We build both and will give you straight numbers for each option on your lot.
Who handles the permits and inspections?
We do, start to finish. That means preparing and filing the permit application, coordinating with your city's planning and zoning staff, scheduling every required inspection as the build progresses, and being on site when the inspector shows up. You should never have to stand in line at a city counter for your own ADU.
Does my HOA have a say in whether I can build an ADU?
Possibly. The statewide law governs what cities must allow, but HOA covenants are a separate layer and can still impose conditions. Before you commit to anything, we review your CC&Rs alongside your lot as part of the free consultation so there are no surprises mid-permit.
Do ADUs need their own utility connections?
Not necessarily. Many ADUs tie into the main house's electrical panel, water, and sewer lines, which keeps costs down. Larger units, or owners planning to rent long-term, sometimes choose upgraded service or separate metering so tenant usage is easy to track. We assess your existing panel capacity and line routing during design and price both approaches before you decide.
What does the free consultation include?
We come to your property, walk the lot with you, look at where a unit could physically sit, check utility access and HOA considerations, and talk through what you want the space to do — guest house, rental, family housing. You get a no-obligation written quote afterward. Call (602) 909-7630 or send us a message to set it up.