Granny flats · Orange County
A granny flat is an ADU built for family.
A granny flat is a permitted, self-contained second home on a lot that already has a house, built so a parent or a relative can live close by with their own kitchen, their own full bath, and their own entrance. California law has no separate category for it: the permit office calls it an accessory dwelling unit, and a granny flat follows the same ADU rules on size, setbacks and review as any other unit.
Avorino builds them across 37 Orange County cities under California General-B License #1107538. Every range here is our published figure; every rule is quoted from the statute named beside it.
Where the name comes from, and what the law calls it.
The name comes from housing a grandparent, and it is not a legal category in California. Government Code §66313 defines the thing itself: an accessory dwelling unit is “an attached or a detached residential dwelling unit that provides complete independent living facilities for one or more persons and is located on a lot with a proposed or existing primary residence,” and it “shall include permanent provisions for living, sleeping, eating, cooking, and sanitation.” That is the whole test, and it says nothing about who lives inside — see what is an ADU and the ADU glossary.
Granny flat, junior ADU, guest house.
Two things get confused with a granny flat. A junior ADU lives inside the house: §66313 defines it as “a unit that is no more than 500 square feet of interior livable space in size and contained entirely within a single-family residence,” and §66333 requires a separate entrance and an efficiency kitchen. A guest house is not an ADU at all — in unincorporated Orange County a guesthouse under Sec. 7-9-91 cannot contain a kitchen and cannot be rented, which is the wrong answer for a parent living independently. The allowances also stack: state law allows one ADU plus one junior ADU on a single-family lot. See junior ADU and guesthouse in the glossary.
Three ways to build one.
A granny flat is built as a detached unit in the back yard (the casita), as an attached unit off a wall of the main house, or as a garage conversion. Detached buys the most privacy; attached is the shortest walk for daily care; a conversion is fastest when the frame is sound. What is an ADU compares all four typologies, and the cost estimator and conversion calculator price one.
Designing one for aging in place.
This is what separates a granny flat from any other ADU, and it is settled at the drawings step. We turn your vision into a buildable blueprint — architectural set, structural engineering, soils when needed. Each item below is an option we draw in, far cheaper as a line on the plan than as a retrofit five years later.
- A no-step, level entry, so a walker or a wheelchair never meets a threshold.
- Wider doorways and clear turning space in the hall, the bedroom and the bath.
- A curbless shower, with blocking in the walls so grab bars can be added later.
- Lever handles on doors and faucets instead of round knobs.
- A single-level plan, bedroom and full bath on the entry level.
- Task lighting where the work happens, low night lighting from bed to bath.
- Laundry inside the unit, so nobody carries a basket across the yard.
- Placement: an entry facing the main house, or a private street-side door — with a covered path either way.
- The yard: one shared garden, or a fenced patio that belongs to the unit.
Two published Avorino plans list it as a use. Bellecielo, at 830 SQFT with two bedrooms and two bathrooms, lists aging-in-place for parents among its use cases; Casielo, at 387 SQFT with one bedroom, lists an in-law suite with independent access. Both are on ADU plan samples. Multigenerational households are the norm in Westminster and Garden Grove, where so many ADUs are built for family instead of tenants.
One Orange County family, in their words.
★★★★★
My parents are getting older and I wanted them close by, so I reached out to several contractors. Avorino really impressed me — extremely professional, timely, and clear communication throughout. The crew was respectful and made me feel comfortable. My parents were so happy with how their space turned out.
Alarah R. · Multi-generational ADU · Orange County · 2023 · See the build
Owner-occupancy, deed restrictions, and renting it later.
For a standard ADU there is no owner-occupancy requirement, and that is state law rather than a courtesy. Government Code §66315 says that on a lot with a single-family dwelling, “No additional standards, other than those provided in Section 66314, shall be used or imposed, including an owner-occupant requirement, except that a local agency may require that the property may be used for rentals of terms 30 days or longer.” So you can build for a parent, live in the main house or not, and let the unit on a long-term lease later — see owner-occupancy in the glossary.
A junior ADU is the exception, and narrower than most sites claim. §66333(b) makes an ordinance require owner-occupancy only “If the junior accessory dwelling unit has shared sanitation facilities with the existing structure,” and even then “The owner may reside in either the remaining portion of the structure or the newly created junior accessory dwelling unit.” It “shall not be required if the junior accessory dwelling unit has separate sanitation facilities.” A junior ADU does carry a recorded deed restriction, which §66333(c) requires to include “A prohibition on the sale of the junior accessory dwelling unit separate from the sale of the single-family residence.” Before the permit issues, Mission Viejo records a city-prepared deed restriction — no short-term rental, no separate sale, junior-ADU owner-occupancy.
Permits and the calendar in Orange County.
Building for a parent changes nothing about the permit path. Under §66317 an ADU application “shall be considered and approved ministerially without discretionary review or a hearing,” and the agency has 60 days “from the date the permitting agency receives a completed application”; if it has not acted, “the application shall be deemed approved.” The word that matters is completed: that clock starts once the application is complete, so correction rounds delay when it starts, and a 4–6+ week plan-check turnaround is typical when the package is complete at intake. Build windows run typically 4–6+ mo for a Junior ADU, typically 4–6+ mo for a garage conversion, typically 5–8+ mo for an attached unit and typically 5–8+ mo for a detached one. The permit index names how each of the 37 cities takes an application.
Paying for it.
Rates and lenders move, so they are not quoted here: see financing and the ADU loan calculator. One correction, because rival pages still advertise it: the CalHFA ADU Grant Program reimbursed up to $40,000 of pre-development and non-recurring closing costs, but its funding was fully allocated in December 2023 and it is not accepting new applications (see the glossary entry).
Granny flat questions, answered
- What is a granny flat?
- A granny flat is a permitted, self-contained second home on a lot that already has a house: its own kitchen, its own full bath, its own entrance. The name says who it is built for — a parent or a grandparent — not a legal category. Government Code §66313 calls the same building an accessory dwelling unit; homeowners also say casita, backyard cottage or in-law suite.
- Is a granny flat the same as an ADU?
- Yes. Granny flat is the everyday word; accessory dwelling unit, or ADU, is what state law and the permit counter call it, and there is one category. It is reviewed on the same ministerial path, under the same setback and floor-area rules, whether a parent, a grown child or a tenant lives in it.
- How much does a granny flat cost in Orange County?
- It is priced by how it is built, not by who lives in it. A garage conversion typically runs $85K – $170K+, a Junior ADU $135K – $220K+, an attached ADU $200K – $350K+, and a detached ADU $245K – $440K+ — Avorino’s published Orange County ranges. Run the ADU cost estimator for a calibrated range on your own lot.
- How big can a granny flat be?
- Government Code §66314 sets the ceilings a city may impose: “The total floor area for a detached accessory dwelling unit shall not exceed 1,200 square feet,” and an attached one “shall not exceed 50 percent of the existing primary dwelling.” State law also allows one detached new-construction unit of up to 800 square feet with four-foot side and rear setbacks (§66323), and §66313 caps a junior ADU at 500 square feet inside the house. An Avorino detached unit finishes at typically 500 – 1,200 sqft.
- Do I have to live on the property if I build a granny flat for my parents?
- For a standard ADU, no: §66315 bars a local agency from imposing “an owner-occupant requirement,” though it may require “rentals of terms 30 days or longer.” A junior ADU is the exception, and a narrower one than most sites state — §66333(b) requires owner-occupancy only “If the junior accessory dwelling unit has shared sanitation facilities with the existing structure,” and even then the owner may live in either portion; a junior ADU with its own sanitation carries no such requirement.
- What happens when my parent moves out or passes away — can I rent it or sell it?
- Renting is the ordinary path: under §66315 a city may require only “rentals of terms 30 days or longer,” so a month-to-month or annual tenancy is what the statute contemplates and short stays are what cities restrict. Selling it separately does not follow — a junior ADU carries a recorded deed restriction that must include “A prohibition on the sale of the junior accessory dwelling unit separate from the sale of the single-family residence” (§66333(c)). For a standard ADU the rule is §66314(d)(1): the unit may be rented separate from the primary residence, but shall not be sold or otherwise conveyed separate from it, subject to the separate-conveyance exceptions elsewhere in the chapter.
- Can I convert my garage into a granny flat?
- Yes, and it is usually the shortest route. §66314(d)(7) provides that “No setback shall be required for an existing living area or accessory structure ... that is converted to an accessory dwelling unit,” and §66314(d)(11) bars a city from requiring replacement of the offstreet parking a converted garage held. A garage conversion typically runs $85K – $170K+ over 4–6+ mo, at 350 – 600 sqft.
Where these rules come from.
Sources: California Government Code §66313, §66314, §66315, §66317, §66323 and §66333. Cities add overlays on top, which is what the permit index tracks.
Tell us who it is for.
Send us the address and who will live in the unit, and we will tell you what the lot can carry before anyone draws. Design, structural engineering, Title 24 calculations and permitting are in-house, on one fixed-price contract. Or call (714) 900-3676.