Close, but not in each other's way
A mother-in-law suite gives a parent, grandparent or adult child their own bedroom, bathroom and usually a small kitchen, on the same property as the main house. It's one of the most common reasons Tucson families build. Done right, everyone keeps their privacy and still shares dinner when they want to.
Attached suite or detached casita?
Attached
An attached suite shares a wall with the house and often has its own outside door plus an inside connection. It's easier for checking in on someone who needs help, and it usually ties into existing plumbing and power. In the City of Tucson, an attached suite with its own kitchen can be an attached ADU. See our ADU builder page.
Detached
A detached casita gives more independence and quiet for both households. It needs its own foundation, roof and utility runs, and the walk between buildings should be level, lit and shaded. In unincorporated Pima County it's permitted as a guest house, which the county describes as used primarily by family members and non-paying guests, a natural fit for a parent.
Our casita vs home addition guide compares both in detail.
Design for now and for later
A suite for a parent who is active today should still work in ten years. Building these features in from the start costs far less than retrofitting them:
- Step-free entry. A level path and a low or zero threshold at the door.
- Wider doorways and clear turning space in the bathroom and bedroom.
- A curbless walk-in shower with a bench and a handheld shower head. Our bathroom team builds these every week.
- Blocking in the walls so grab bars can go in now or later without opening the wall.
- Lever handles on doors and faucets.
- Switches and outlets at easy reach, and good lighting from bed to bathroom.
- Everything on one level, including laundry if possible.
Many of these appear in the "inclusive home design" notes Pima County asks for on new custom home plans, covering the accessible route and entrance, door widths, thresholds, lever hardware, grab-bar reinforcement and electrical heights (Pima County custom home submittal).
Rules that apply to your lot
- City of Tucson: under Arizona's HB 2720, the city must allow at least one attached and one detached ADU on a single-family lot, up to 75% of the main home's floor area or 1,000 sq ft, whichever is smaller, with no extra parking required.
- Unincorporated Pima County: a detached unit follows the guest house rules: one per lot, a 4,000 sq ft minimum lot, shared driveway, no separate meter. The county also has a temporary secondary dwelling permit for a manufactured home in GR-1 or RH zones, for a relative or a person needing care.
- Oro Valley, Marana and Sahuarita: each town has its own code and permit office, and HOA approval usually comes first.
Our Tucson casita rules guide explains how to find your jurisdiction.
Practical details families forget
- Cooling: a dedicated mini-split lets each household set its own temperature.
- Sound: insulated shared walls keep two schedules from colliding.
- Laundry: a stacked washer and dryer in the suite saves trips across the house or yard.
- Kitchen size: a kitchenette may be enough if meals are often shared, and it saves space and budget.
- Septic: on county septic lots, an extra bedroom and bathroom can mean the system needs to be checked first.
- Matching the house: same stucco and roof, so it looks original. We do both in house.
- Parking and paths: a short, level route from where the car stops to the suite door matters more than people expect.
- Who decides: involve the person moving in early. Their routines should shape the layout, from which side of the bed they get up on to where the morning sun lands.
How we build a mother-in-law suite
We walk the property, talk with you (and ideally the person moving in) about daily routines, confirm the rules for your lot, and give you a written estimate. One licensed contractor (AZ ROC #344537) handles foundation, framing, roofing, stucco and the bathroom. For layout ideas see our casita floor plans guide, and for budgets the casita cost guide and home addition cost guide.