Casitas · Orange County
A casita is a little house on your lot. In California it is a detached ADU.
Casita is Spanish for little house, and in California a casita you can actually live in is permitted as a detached ADU — an accessory dwelling unit with, in the words of Government Code §66313, permanent provisions for living, sleeping, eating, cooking, and sanitation. In Orange County, Avorino designs and builds them at 500 – 1,200 sqft, typically $245K – $440K+ over 5–8+ mo.
The ranges on this page are Avorino’s published Orange County figures, across the 37 cities we build in, under California General-B License #1107538.
What a casita is, and what the permit calls it.
Casita is what people in Southern California call the small standalone home at the back of a lot. It is a vernacular word, not a legal one: the permit application does not use it. What goes in instead is an application for an accessory dwelling unit, and because a casita stands apart from the main house, what gets approved is a detached ADU. California defines the thing precisely: Government Code §66313 calls an accessory dwelling unit “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 says it “shall include permanent provisions for living, sleeping, eating, cooking, and sanitation.” That last clause is the whole test. Avorino publishes the same equivalence on the ADU hub: an accessory dwelling unit is also called a granny flat, casita or backyard cottage. For the depth, read what an ADU is and the detached ADU entry in the glossary.
Casita, guest house, or pool house?
The line between them is not size or style or where the building sits in the yard. It is whether the building has permanent cooking and sanitation of its own. A structure with a bedroom and a bathroom but no kitchen is an accessory structure — a guest house or a pool house. It is permitted as an accessory building rather than as a home, and the restrictions can be firm: in unincorporated Orange County, county code Sec. 7-9-91 says a guesthouse cannot be rented at all and cannot contain a kitchen. Add permanent cooking and sanitation and the same building crosses the line drawn in §66313: it becomes a dwelling, permitted as a second home on the lot, inspected as one, and rentable for terms of 30 days or longer under state law. That single decision changes the drawings, the utilities and the approval path, so settle it early rather than at plan check.
How big a casita can be, and what one costs.
State law brackets the size from both ends: §66314(d)(5) caps a detached unit at 1,200 square feet of floor area, and §66321(b)(2) bars a city from capping one below 850 square feet of interior livable space, or below 1,000 square feet where the unit has more than one bedroom. The lot-coverage, setback and 800-square-foot by-right rules are set out on the detached ADU page. Inside that envelope, this is what Avorino publishes for the type a casita is built as.
| Typical size | 500 – 1,200 sqft |
|---|---|
| Bedrooms | Studio – 3 BR |
| Typical cost | $245K – $440K+ |
| Build window | 5–8+ mo |
| Includes | New foundation, full kitchen + bath, independent utilities. |
| Best for | Properties with side or rear setback room for a free-standing unit. |
What moves the number inside the band.
Square footage first. Then whether the design goes to a second story, how far the sewer, water and electrical runs have to travel, the finish level you choose, and how much room the crew has to reach the back of the lot. Those five decide where a project sits between the two ends of the range above. The ADU cost estimator prices a build for your city, square footage and finish level in about a minute; the ROI calculator turns that into rent and payback; and financing covers how owners pay for one, with the investment case beside it.
The rules, in short.
Four things cover most of what a casita has to satisfy. Approval is ministerial — no hearing, no design board — and the city has 60 days from a completed application, after which it is deemed approved (§66317). A city may require no more than four feet of side and rear setback for a new-built unit (§66314(d)(7)). Height has a floor a city must allow: 16 feet for a detached unit, and 18 feet near a major transit stop or on a lot with a multifamily, multistory dwelling (§66321(b)(4)). And no city may impose an owner-occupant requirement, though it may require rentals of 30 days or longer (§66315). The full state standard set for a detached unit lives on the detached ADU page, and how each of the 37 Orange County cities actually takes the application is indexed on the Orange County ADU permit index. We take care of the submission, the comments and the resubmittal to the city.
Casitas we have built.
Three permitted detached ADUs and one ground-up pool house — the Ground-Up Custom Pool House, which we publish as a custom build rather than as a permitted ADU. Sizes and room counts marked approx. are estimates from plans and photos.The two-story figure is the owner’s own.
Detached ADU · Santa Ana Hills1,000 Sq Ft Two-Story ADU1,000 sq ft · 2 bed · 2 bath · Two-story · Ground-up
Detached ADU · Santa AnaDetached ADU in Santa Anaapprox. 800 sq ft · approx. 2 bed · 2 bath · Single-story · Ground-up · Flat lot
Detached ADU · Buena ParkStriped-Awning Detached ADUapprox. 750 sq ft · approx. 2 bed · 2 bath · Single-story · Ground-up · Flat lot
Custom Build · San Juan CapistranoGround-Up Custom Pool Houseapprox. 900 sq ft · approx. Studio · 1 bath · Single-story · Ground-up
Designing one for your lot.
Most of the design is settled by the lot rather than by preference: where the four-foot side and rear setbacks land, whether the yard has room for a single story or has to go up, and where the utilities can cross. Pool, patio and mature trees decide the rest. Start from our ADU plan samples, see the finished work on the portfolio, or put your own build on your own lot with photoreal rendering before anything is drawn for permit.
Casita questions, answered
- Is a casita the same as an ADU?
- In California, a casita you can live in is an ADU — almost always a detached one. Government Code §66313 defines an accessory dwelling unit as a residential dwelling unit that “provides complete independent living facilities,” with “permanent provisions for living, sleeping, eating, cooking, and sanitation.” Avorino publishes the same equivalence: an accessory dwelling unit is also called a granny flat, casita or backyard cottage. A guest room or pool house with no kitchen is an accessory structure, not an ADU.
- How much does a casita cost in Orange County?
- A casita is built and permitted as a detached ADU, and Avorino publishes that type at typically $245K – $440K+ for 500 – 1,200 sqft. What the band covers: New foundation, full kitchen + bath, independent utilities. Where a project lands inside it comes down to size, stories, utility runs, finish level and site access. The Avorino ADU cost estimator prices your own city, square footage and finish level in about a minute.
- Do I need a permit to build a casita?
- Yes — a casita is permitted as a dwelling, not as an accessory building. Government Code §66317(a)(1) says an ADU application “shall be considered and approved ministerially without discretionary review or a hearing,” so there is no design board and no neighbor vote. §66317(a)(3) gives the city 60 days from a completed application, after which it “shall be deemed approved.” The clock starts at completeness, not at first submission, which is why we carry the comments and the resubmittal.
- How big can a casita be?
- Within the state bracket: §66314(d)(5) caps a detached unit at 1,200 square feet of floor area, and §66321(b)(2) bars a city from capping one below 850 square feet of interior livable space, or below 1,000 square feet where the unit has more than one bedroom. Avorino builds detached units at 500 – 1,200 sqft, Studio – 3 BR; the full state standard set is on the detached ADU page.
- How long does a casita take to build?
- Construction on a detached unit typically runs 5–8+ mo, with design, engineering and the city's 60-day review of a completed application (§66317(a)(3)) ahead of it; we do not publish a single end-to-end number, and the permit mechanics are on the detached ADU page.
- Can I rent out my casita?
- Government Code §66315 bars any standard beyond those in §66314, “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 a city cannot make you live on the property, and it can require rentals of 30 days or longer rather than by the night. Run the rent and payback numbers on the Avorino ROI calculator.
- Can a casita be two stories?
- Yes — Avorino has built one, the 1,000 Sq Ft Two-Story ADU in Santa Ana Hills. Whether yours can depends on the lot: Government Code §66321(b)(4) bars a city from setting a height limit below 16 feet for a detached unit, or below 18 feet near a major transit stop or on a lot with a “multifamily, multistory dwelling,” and those are floors, not ceilings; the full standard set is on the detached ADU page.
Sources.
Every statutory quote above is from the California Government Code:
- Gov. Code §66313 — what an accessory dwelling unit is
- Gov. Code §66314 — development standards, setbacks, floor area
- Gov. Code §66315 — no owner-occupancy requirement; 30-day rentals
- Gov. Code §66317 — ministerial approval and the 60-day clock
- Gov. Code §66321 — minimum sizes and height a city must allow
- Gov. Code §66323 — the by-right 800 sq ft detached unit
See what your lot can take.
Send us the address and the casita you have in mind. Avorino handles design, structural engineering, Title 24 calculations and permitting in-house, on one fixed-price contract, across 37 Orange County cities.