ADU types
Mother-in-law suite vs ADU: what the terms mean
By the HyreADU research desk. Last checked .
The short answer
A mother-in-law suite and an ADU are often the same thing in everyday speech, but not in law. “In-law suite” or “in-law unit” is an informal name for living space for a relative.
Legally, it is either part of the house, a junior ADU (in California, inside the house, up to 500 sq ft), or a full ADU with its own kitchen, bathroom and entrance.
| Name people use | What it usually is legally | Separate kitchen and entrance |
|---|---|---|
| In-law suite inside the house, no kitchen | Part of the main house | No |
| In-law suite with an efficiency kitchen and own door | Junior ADU in California, if 500 sq ft or less | Efficiency kitchen; own entrance |
| In-law unit in the backyard | Detached ADU | Yes |
| In-law apartment over the garage | Attached or detached ADU | Yes |
Why the legal category matters
The legal category decides the permit, the fees and whether the space can be rented. A suite that is part of the house is built under a remodel or addition permit.
A JADU or ADU is approved under state ADU law, which in California means ministerial review and a 60-day decision on a complete application (Gov. Code §§ 66317, 66335).
The kitchen line
The kitchen is usually where an in-law suite becomes a unit. California defines an ADU as having complete independent living facilities, including permanent provisions for cooking (Gov. Code § 66313). A JADU needs an efficiency kitchen. Adding a stove to a suite without the right permit can create an unpermitted unit.
Choosing the right form
- Your parent wants to share meals and help is close: a suite inside the house.
- Your parent wants a door and kitchen but the space is inside the house: a JADU.
- Your parent wants a separate home: a detached or attached ADU.
Compare on ADU vs in-law suite and JADU vs ADU.
Later uses
Families change, so plan for the next use. A JADU or ADU can later house a caregiver or a tenant, within local rules on rental terms. A suite that is part of the house cannot be rented as its own unit. Read ADU for aging parents.
A mistake to avoid
The mistake to avoid is calling a space an in-law suite to skip the ADU permit. If it has a kitchen, a bathroom and its own door, the building department is likely to treat it as a unit, and unpermitted units can surface at sale or on an insurance claim.
What to do next: check your lot with the ADU feasibility checker, read the questions to ask an ADU builder, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.
Get ADU optionsQuestions
Is an in-law suite an ADU?
Only if it is permitted as one. Otherwise it is part of the house.
Can an in-law suite have a kitchen?
A full kitchen usually makes it an ADU or JADU, which needs that permit.
Do I need a permit for an in-law suite?
Yes, any remodel or addition that changes rooms or systems needs a building permit.
Can I rent an in-law suite?
As a room, under local rules. As a separate unit, only if it is permitted as a JADU or ADU.
Sources
- Gov. Code § 66313 (ADU and junior ADU definitions). Checked October 7, 2026.
- Gov. Code § 66317 (ministerial review, completeness and the 60-day decision). Checked September 5, 2026.
- Gov. Code § 66335 (junior ADU permit decision). Checked September 5, 2026.
- Gov. Code § 66333 (junior ADU ordinances). Checked October 7, 2026.
HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax, lending or engineering advice.
Rules vary by state and city; California rules are labeled as such. Spotted an error? Tell us through our corrections page. Licensed professionals can also contribute as named sources.