ADU Constructionin Gardena, CA
ADU construction in Gardena is approved ministerially under Municipal Code Chapter 18.13: the City must decide a complete application within 60 days, or 30 days on a City preapproved plan. An ADU can reach 850 square feet for a studio or one bedroom and 1,000 for two or more, and 800 square feet is guaranteed.
Gardena's streets were laid out over old strawberry fields for a population that grew from 5,909 in 1940 to 41,021 in 1970, and 43.8 percent of today's 21,837 housing units, 9,566 homes, are single-family detached houses. The median year built across all units is 1964. A back yard or a garage on one of those lots is the raw material for an accessory dwelling unit.
This page covers the City's new ADU chapter, Ordinance 1893 of September 8, 2026, the preapproved plan program that sits beside it, garage conversions, soils and utilities, and the other two-unit paths on a single lot. Cost ranges and the build timeline are on our ADU construction page.
What the Gardena Municipal Code says about ADUs and JADUs
Where adu construction permits come from in Gardena: City of Gardena Community Development Department, Building and Safety Division.
- Chapter 18.13 of the Gardena Municipal Code (rewritten most recently by Ordinance 1893, dated 9/8/2026, after Ordinance 1883 of 2025) governs ADUs and JADUs under Government Code Sections 66310 to 66342, and says where the chapter conflicts with other zoning provisions it prevails and where it conflicts with state law the mandatory state requirement controls. The City's ADU page confirms the standards are in Chapter 18.13.
- The City must tell an ADU or JADU applicant within 15 business days whether the application is complete (otherwise it is deemed complete) and must ministerially approve or deny a complete application within 60 days; a plan preapproved by the City, or identical to a detached ADU plan approved within the current triennial code cycle, gets a 30 day decision. A denial must come with written comments and the applicant may appeal a denial or an incompleteness finding directly to the City Council, which owes a written determination within 60 days of the appeal.
- When a detached garage is replaced with an ADU, the demolition permit is reviewed with the ADU application and issued at the same time, and an ADU application filed with a new single-family or multifamily dwelling is not acted on until the dwelling application is approved (NMC 18.13.020).
- ADUs are allowed on every legally existing residentially zoned lot with a single-family dwelling or an existing or proposed multifamily structure, and on mixed-use lots with a dwelling, and an ADU may be built in an attached or detached garage or an existing accessory structure (NMC 18.13.030). The chapter says it does not override HOA covenants to the extent those comply with state law.
- Only one ADU or one JADU is allowed per residential lot unless the mandatory approval rules allow a combination, an ADU cannot be sold separately from the primary dwelling (except to a qualified nonprofit under Government Code 66341), and no unit on the property may be rented for fewer than 31 consecutive days (NMC 18.13.040). ADUs and JADUs do not count toward density and are allowed regardless of lot coverage, open space, floor area ratio and minimum lot size standards.
- Impact fees are not charged on a JADU or on an ADU of 750 square feet or less of interior livable area, and for larger ADUs impact fees are proportional to the square footage of the primary dwelling. An ADU is not treated as a new residential use for utility connection fees or capacity charges unless built with a new single-family dwelling, and an ADU inside an existing single-family dwelling gets no new connection fee (NMC 18.13.040).
- Size limits (NMC 18.13.050 E): an attached or detached ADU may not exceed 850 square feet of interior livable space for a studio or one bedroom or 1,000 square feet for more than one bedroom, and the development standards are waived as needed to allow an 800 square foot ADU within the height limit and with four foot side and rear setbacks.
- Setbacks (NMC 18.13.050 F): none for a converted living area or accessory structure, or a new ADU built in the same location and to the same dimensions; no more than four feet at the sides and rear for other ADUs; at least six feet from other buildings on the lot or an adjacent lot; behind the front yard setback unless replacing an approved structure in the same spot; and no encroachment into an easement without the easement holder's written permission (a sworn declaration creates a rebuttable presumption of compliance).
Sources for these rules
Can you build an ADU in Gardena? Size, height and setbacks under Chapter 18.13
Yes, on every legally existing residential lot with a single-family house or a multifamily building. Chapter 18.13, last rewritten by Ordinance 1893 after Ordinance 1883 of 2025, says its rules prevail over other zoning, and where it conflicts with state law the mandatory state rule controls. The chapter is on ecode360, and the City summarizes the program on its ADU page.
An attached or detached ADU may reach 850 square feet of interior living space for a studio or one bedroom and 1,000 for two or more, and the code waives standards as needed to allow 800 square feet with four foot side and rear setbacks. A detached unit tops out at 16 feet, or 18 feet within half a mile walking distance of a major transit stop. An attached unit or one over a garage may reach 25 feet or the zone limit, never above two stories.
Setbacks are four feet at most on the sides and rear, none for a conversion or a rebuild in the same spot and to the same dimensions, and six feet from other buildings. Parking is one space for an ADU with a bedroom, none for a studio or a unit made from existing space, and nothing has to be replaced when a garage is converted.
Gardena's preapproved ADU plans: what they save and what they do not
Gardena runs a Preapproved ADU Plans program for detached units drawn by designers, architects and builders. A City-approved plan, or one identical to a detached plan approved in the current triennial code cycle, gets a 30 day decision instead of 60. The plans are for new construction only, are bought from the designer, and the City takes only credit or debit cards for the program.
A preapproved set is not a finished permit package. Each lot still needs site-specific plans, studies and engineering, and any modification sends the project to regular ADU plan review. The site plan is where a standard design meets a real lot: the four foot setbacks, six feet between buildings, the existing garage and an easement if one crosses the yard.
Designs that fit the 800 square foot size state law guarantees stay inside the one set of rules a city cannot add to. Larger units trade that certainty for the chapter's own standards, including a separate entrance on a different plane than the main house's entrance.
Garage conversion to an ADU in Gardena: parking, demolition and the two-car rule
Gardena zoning normally requires a two-car enclosed garage, at least 20 by 20 feet inside, for a single-family home. The ADU chapter overrides that for conversions: no replacement parking is required when a garage or carport is demolished or converted, and a unit may be built inside an attached or detached garage or an existing accessory structure. A garage unit plus a junior unit inside the house can qualify for the mandatory approval track, with up to 150 square feet added for access.
When a detached garage is replaced with a new ADU, the demolition permit is reviewed with the ADU application and issued at the same time. A unit built above a garage needs a recorded declaration that the garage stays available for parking. Our post on garage conversion permit steps was written for the City of Los Angeles, so use it for the sequence of steps and not for Gardena's rules.
Because the garage rules are easy to misread, ask Planning at (310) 217-9524 to confirm in writing how the City will treat the garage on your lot before design starts.
Utilities, soils and grading: the ground rules under a Gardena ADU
A unit that is not inside the existing house gets its own utility connection. An ADU is not treated as a new residential use for connection or capacity fees unless it is built with a new house, and an ADU inside an existing house gets no new connection fee. Ask the water, sewer and electric providers what they require before the trench is priced, because trenching to the street is a separate line from the building.
Hazards are narrow in Gardena, not citywide. The City's Public Safety Plan places a State liquefaction zone along Artesia Boulevard and the Dominguez Channel on the southern side, and 92 of the 2,283 sample points we checked, 4.0 percent, fell inside that strip. One sample touched an Alquist-Priolo fault zone near El Segundo Boulevard and Vermont Avenue. Those are samples and not parcel maps, and no mapped fire zone covers the city. Policy PS 3.2 calls for geotechnical studies on new development, so ask whether a detached ADU triggers a soils report.
Grading is a separate review when work generates 50 cubic yards or more of combined cut and fill, with a plan stamped by a California civil engineer. The City's stormwater checklist applies when work alters 50 percent or more of a lot's impervious surface.
How long does an ADU permit take in Gardena? The 15 business day and 60 day clocks
The City must tell an applicant within 15 business days whether the application is complete, or it is deemed complete, and must then approve or deny a complete application within 60 days. A denial comes with written comments, and the applicant can appeal a denial or an incompleteness finding directly to the City Council, which owes a written determination within 60 days of the appeal.
The mechanics matter as much as the clock. Applications go in by email as PDFs, the City works out the plan review fee, sends notice through Microsoft Teams and starts review only after the card payment, and an applicant who gets no notice within 48 hours is told to call (310) 217-9672. An ADU filed with a new house waits until the house application is approved.
Permit validity has the same conflict as other Gardena jobs. The permit page says 180 days unless work is active, and Municipal Code 15.06.030 says 12 months to start or 12 months suspended, so ask Building and Safety which governs. MDG Builders, CSLB #1040337, designs the unit, files the application and runs the schedule, while licensed specialty subcontractors pour the slab, frame, wire and plumb it.
ADU, JADU or SB 9 two-unit project: what Gardena allows on one lot
Only one ADU or one JADU is allowed per lot unless the mandatory approval rules allow a combination, such as one ADU and one JADU inside the existing or proposed house or an accessory structure. A JADU is capped at 500 square feet, must sit inside the house (an attached garage counts), needs an efficiency kitchen and a separate entrance, and carries a recorded deed restriction. Our ADU versus JADU guide explains the difference.
Rental and sale rules apply to every unit: no unit on the property may be rented for fewer than 31 consecutive days, and an ADU cannot be sold apart from the main house except through a qualified nonprofit under state law. ADUs and JADUs do not count toward density and are allowed regardless of lot coverage, open space, floor area ratio and minimum lot size.
SB 9 is a different track. Municipal Code 18.12.060 allows a ministerial two-unit development on a single-family lot with a 60 day decision, four foot side and rear setbacks and a 20 foot front setback, and Chapter 18.45 sends two-unit projects through design review against objective standards. The fee schedule lists an Urban Lot Split at $1,745. Our guide to room addition versus ADU helps choose between the paths.
Legalizing an old backyard unit in Gardena: the AB 2533 route
In a city where 71.5 percent of housing units predate 1980, some lots carry a converted garage or back unit that nobody permitted. For a unit built or converted before January 1, 2020, the City runs an AB 2533 process: the owner proves the construction date with County Assessor records, a title report, City records or a transfer disclosure, a licensed California B contractor, architect or engineer completes a Substandard Housing Inspection Checklist, and the owner files a site plan, floor plan and photographs.
Municipal Code 18.13.025 bars denying a permit for such a unit solely because it violates building standards or the City's ADU rules, unless correcting the violation is needed for health and safety under Health and Safety Code 17920.3, and it bars penalties and most impact or connection fees. The owner may get a confidential third-party inspection first, which shows the list of problems before the City sees it.
ADU details from South Bay builds
Three views of the slab, framing and interior finishes behind a backyard unit in the South Bay. Tap a photo to enlarge it.
What adu construction costs around Gardena
Regional ranges on our ADU construction page are about $100,000 to $200,000 for a garage conversion and $200,000 to $400,000 for a new detached ADU of 400 to 800 square feet, a synthesis of the Berkeley and Terner Center surveys, the 2025 Cost vs. Value report and builder quotes, with medium-low confidence. We found no Gardena cost survey, and the ADU cost guide shows the sources. The City's permit table gives $2,179 for a $200,000 valuation, with plan check equal to that, if the residential table applies to your unit, and an ADU of 750 square feet or less pays no impact fee. Compare Hawthorne, Torrance, Inglewood, Carson and Los Angeles. A unit with its own bath links to bathroom remodeling in Gardena, a bigger main house to a Gardena room addition, and new glass to window replacement in Gardena. Start at the Gardena overview.
| What it covers | Typical range |
|---|---|
| Garage conversion to a studio or one bedroom | $100,000 to $200,000 |
| New detached ADU, 400 to 800 sq ft | $200,000 to $400,000 |
| UC Berkeley survey, Los Angeles County median, 2018 and 2019 projects | $100,000 overall. $90,000 garage. $180,000 detached. |
| Terner Center and Berkeley CCI, 2020 | $148,000 Los Angeles estimate. $167,000 statewide average. |
| Remodeling Cost vs. Value 2025, Los Angeles | $178,536 job cost |
| Electrical and plumbing, Angi Los Angeles, January 2026 | Electrical $2,600 to $7,800. plumbing $3,900 to $10,400. |
| City permit and plan check fees | Not priced here |
ADU size, parking, fee and timing questions for Gardena lots
How big can an ADU be in Gardena?
An attached or detached ADU may reach 850 square feet of interior living space for a studio or one bedroom and 1,000 square feet for more than one bedroom. The code also waives standards as needed to allow an 800 square foot unit with four foot side and rear setbacks. A JADU is limited to 500 square feet and must sit inside the house.
Do I need to provide parking for my ADU?
Often not. The code requires one space for an ADU with a bedroom, none for a studio or a unit created in existing living space, and no replacement parking when a garage or carport is converted or demolished. None is required within half a mile walking distance of transit or within one block of a car share vehicle.
How long does it take to get an ADU permit?
The City must say within 15 business days whether an application is complete and decide a complete one within 60 days, or 30 days on a City preapproved plan. Those are decision clocks, not construction time. Applications are emailed as PDFs, and review begins only after the plan review fee is paid.
How much does it cost to build an ADU in Gardena?
Budget about $100,000 to $200,000 for a garage conversion and $200,000 to $400,000 for a new detached unit of 400 to 800 square feet. Those ranges blend the Berkeley and Terner Center surveys, the 2025 Cost vs. Value report and builder quotes. No Gardena survey turned up, so a written proposal for your lot is the real price.
Do I have to pay impact fees on an ADU?
Not on a JADU or an ADU of 750 square feet or less of interior living area. For a larger ADU, impact fees are proportional to the square footage of the main house. Utility connection and capacity charges are separate, and none applies to an ADU created inside an existing single-family house.
Can I convert my garage to an ADU?
Yes. The code allows an ADU inside an attached or detached garage or existing accessory structure, with no replacement parking required. A garage unit plus a JADU inside the house can qualify for mandatory approval, with up to 150 square feet added for access. Ask Planning how the City will treat the two-car garage rule on your lot.
Can I rent my ADU on Airbnb in Gardena?
Not on a short-term basis. No unit on the property may be rented for fewer than 31 consecutive days. Long-term rentals are allowed, owner occupancy is not part of the ADU rules we read, and a JADU's recorded deed restriction limits how it can be rented. Check any HOA covenant as well, since the chapter does not override those.
What is the difference between an ADU and a JADU?
A JADU is capped at 500 square feet and must sit inside the single-family house, an attached garage counting, with an efficiency kitchen and a separate entrance. An ADU can be attached or detached and reach 850 or 1,000 square feet. One ADU plus one JADU can be combined under the mandatory approval rules, and SB 9 two-unit projects are a separate path.
Can I sell my ADU separately from the main house?
No, not in the usual way. An ADU cannot be sold separately from the primary dwelling except to a qualified nonprofit under state law. Ask an attorney about condominium options, because the Gardena chapter we read does not describe one. Rentals of 31 days or more are the rule on the property, so a sale is a separate question from income.
Can I legalize an unpermitted garage or back unit in Gardena?
Possibly, if it was built or converted before January 1, 2020. The City's AB 2533 process asks for proof of the construction date and a Substandard Housing Inspection Checklist completed by a licensed B contractor, architect or engineer. A permit cannot be denied solely for building-standard violations unless correction is needed for health and safety.
Tell us about your Gardena lot
Tell us which part of Gardena the lot is in, whether you want a garage conversion or a new backyard unit, and whether the house has a detached garage, and we will plan the site visit around that.