Building an ADU in Gardena. Rules, costs, timeline.

Can I build an ADU in Gardena?

Five things to know before you start

If you read nothing else here, read these. They are the five points that change the most Gardena projects.

Everything in this section comes from Gardena Municipal Code Chapter 18.13 (Ordinance No. 1883, adopted June 10, 2025), read against Gov. Code §§ 66310–66342 and HCD’s May 8, 2026 ordinance-review letter to the City. We will not re-cite the local chapter on every line; assume it under each heading unless we say otherwise.

How many units a Gardena lot allows

The ordinance opens narrow and the statute opens wide, and the statute wins. Here is the stack state law requires on a lot with a single-family home:

Three accessory units on top of the house you already have. Most Gardena homeowners assume the limit is one, because that is how the ordinance reads on its face.

Multifamily lots

If your property holds an existing apartment building the numbers get larger. SB 1211 amended Gov. Code § 66323(a)(4)(A)(ii) effective January 1, 2025 to allow up to eight detached ADUs on a lot with an existing multifamily dwelling, capped at the number of existing units. Clause (iii) allows two on a lot with a proposed multifamily dwelling. Converted units in non-livable space are counted separately again, at a minimum of one and up to 25 percent of the existing unit count. Junior ADUs are a single-family device and are not available on a multifamily site.

Owner-occupancy

You do not have to live on the property. Gov. Code § 66315 bars a city from imposing an owner-occupancy requirement on an accessory dwelling unit, and Gardena’s ordinance imposes none.

A junior ADU is the exception, and a narrower one than the local text suggests. GMC § 18.13.070 H.4 requires a recorded deed restriction that the owner live in either the house or the junior unit. AB 1154, effective January 1, 2026, amended Gov. Code § 66333(b) so the requirement reaches only a junior ADU that shares sanitation facilities with the house. HCD’s tenth finding tells the City to amend the ordinance to say so. Give the junior unit its own bathroom and the requirement does not apply to you, whatever the ordinance still says.

What an ADU costs in Gardena (2026)

Our Signature plans are fixed-price, and the number is the same whether the lot is in Gardena, Torrance or the Valley. Construction is separate: once your plans are permitted, you build it yourself, bring your own licensed contractor, or build with one of our vetted construction partners. The figures below are the estimated cost to build each model with an independent licensed general contractor.

City fees

Gardena publishes no flat ADU fee. Building permit and plan check are set from construction valuation, so they scale with what you build. Under the City’s Adopted User Fee Schedule effective July 1, 2026, a residential project valued between $100,001 and $500,000 pays a building permit of $1,429 plus $7.50 per $1,000 of valuation above $100,000. Building plan check is billed at 100% of that permit. The same schedule carries further plan-check lines, including a Title 24 and energy review, so confirm the full plan-check total with Building and Safety rather than assuming a single charge. Add a $72 permit issuance fee, separate electrical, plumbing and mechanical permits at $70 issuance each, the SB 1473 and SMIP state surcharges, and a $366 Public Works sewer connection where a new lateral is needed. We pass all of these through at cost and itemize them for your lot before you commit.

Impact fees are the part state law controls, and the line is sharp. An ADU with 750 square feet of interior livable space or less is exempt outright, and so is a junior ADU at 500 or less (Gov. Code § 66311.5(c)(1)). The threshold is inclusive, so a unit at exactly 750 pays nothing. Above the line the fee must be charged in proportion to the square footage of the primary dwelling — the ADU’s area divided by the house’s — rather than at the full rate a new home would pay. A unit with less than 500 square feet also sits outside school district fees (§ 66311.5(c)(3)).

Utility connections follow their own rule and it is worth knowing before you choose a type. A conversion approved under Gov. Code § 66323(a)(1) cannot be made to install a new or separate utility connection, and no connection fee or capacity charge may be imposed on it (§ 66311.5(d)). A new detached unit is different: the City may require its own connection and charge a fee proportionate to the burden it places on the system (§ 66311.5(e)). Gardena also requires new utility lines to run underground (GMC § 18.13.050 I). That is a real line in a South Bay budget. It is also a local standard, and HCD’s eighth finding says no § 18.13.050 standard that state law does not authorize may be applied to a unit approved under Gov. Code § 66323.

What it returns

Long-term tenancy is the only option here. GMC § 18.13.040 C sets a minimum rental term of 31 consecutive days that reaches every residence on the lot, and state law sets the same floor for units approved on the Gov. Code § 66323 track (§ 66323(e)) and for junior ADUs (§ 66333(g)).

For a government benchmark, HUD publishes Fair Market Rents for the Los Angeles–Long Beach–Glendale metro area. Read them as a floor rather than a forecast: they cover the whole metro across all housing stock and ages, including units decades older than anything you would build.

A new, well-finished detached ADU typically rents above these figures. Every Signature Home maps onto a band — the Melrose rents as a two-bedroom, the Lincoln as a three — and the full lineup with build costs is in the table above. For payback math keyed to your lot and financing assumptions, use the ADU ROI calculator.

HUD FMR figures: FY 2026 Fair Market Rents, Los Angeles–Long Beach–Glendale HUD Metro FMR Area, as revised effective May 21, 2026 (91 FR 21301, published April 21, 2026). No published Gardena-specific rent survey is available to cite, so none is estimated here.

Why the Gardena market rewards the build

Gardena is a working South Bay city of about 61,000 people, built on flat, regular postwar lots. It is ringed by the 110, the 91 and the 405, and within easy reach of the ports, the aerospace corridor and the LAX job base. That profile produces steady long-term tenants rather than seasonal ones, which suits a market where the law requires a 31-day-plus tenancy anyway.

The lots themselves are the quieter advantage. Rectangular parcels with rear access and a detached garage are common here. Both of the routes this page spends the most time on suit that geometry exactly: a garage conversion with no setback and no replacement parking, or a unit built above the garage at two stories.

When an ADU isn’t the right move

A guide that never says “not you” is a brochure. Four situations where a Gardena ADU is the wrong call, or the wrong call right now.

• Your plan depends on nightly rental income. GMC § 18.13.040 C requires a 31-day minimum term across every residence on the lot, and Gov. Code § 66323(e) sets the same floor from the state side. If short-term rental is the business case, there is no version of this that works.
• You are counting on selling the unit separately. Gardena has not adopted an AB 1033 opt-in, so the condominium route at Gov. Code § 66342 is closed. The one path state law forces open runs through a qualified nonprofit under § 66341 and does not describe a typical homeowner sale.
• You wanted a two-story building in the backyard. The detached envelope tops out at 20 feet on the most favorable lot in the city. Two stories means attaching to the house or building above a garage, at 25 feet or your zone’s limit if that is lower — a different building against a different wall, not the same project with an extra floor. The attached route also runs into the 50-percent-of-the-house cap in Gov. Code § 66314(d)(4), which state law floors at 800 square feet rather than 1,000.
• You are budgeting on the preapproved-plan catalog. The City is still gathering plans from designers, and it posts them as they clear review (Gov. Code § 65852.27(a)(4)). Check the City’s ADU page for what is actually listed before you count on the design saving. Two limits also apply: modifying a preapproved plan drops the project back onto the regular 60-day track, and the 30-day lane reaches detached units only.

The rules that make Gardena different

Where the ordinance falls behind state law

Ordinance No. 1883 was adopted on June 10, 2025 and submitted to the California Department of Housing and Community Development, which received it on June 17, 2025. On May 8, 2026 HCD reviewed it under Gov. Code § 66326(a) and issued ten numbered findings that it does not comply with State ADU Law. The City was asked for a written response by June 7, 2026, with a plan either to amend the ordinance or to adopt a resolution explaining why it believes the ordinance complies. As of our last verification of Chapter 18.13 on August 25, 2026, the ordinance had not been amended.

These are the findings that change what a Gardena homeowner may build:

Read the shape of that list before the detail. Roughly half of it — numbering, the application process, the fee wording, how size is measured — is drafting the City has to repair. The other half changes what you may build: findings 6 through 10 reach setbacks, placement, which local standards may touch a Gov. Code § 66323 unit, where a junior ADU’s door goes, and who has to live on the property.

Two sections are not named anywhere in the letter: GMC § 18.13.050 G, the height rules, and § 18.13.050 H, the parking rules. That is worth knowing, but it is not a clean bill of health — the letter certifies no section as compliant, and its eighth finding says § 18.13.050 contains standards state law does not authorize. So this page states the height tiers and parking exemptions against the state floors at Gov. Code §§ 66321(b)(4), 66314(d)(10) and 66322, which control whatever the local text does.

The above-garage two-story route

This is Gardena’s most useful local difference and it is easy to miss, because the ordinance files it inside the height rules. GMC § 18.13.050 G.4–5 allows an ADU that is attached to the primary dwelling or built above a garage to reach 25 feet and two stories, and it does not limit that to an attached garage. The state floor at Gov. Code § 66321(b)(4)(D) addresses only attached units, so a detached garage with a unit above it is a route the City offers rather than one the state requires.

On a typical Gardena lot with a detached garage at the rear, that turns a single-story problem into a two-story option without touching the yard. The ceiling is 25 feet, or your zone’s height limit for the house where that is lower. One condition comes with the route. Our June 2026 read of § 18.13.050 G.4–5 recorded a required declaration, recorded against the property, that the garage below stays in use for parking. We have not been able to re-verify that since, because the City’s code publisher has been unreachable. Treat it as likely and confirm it with the Planning Division before you design around it.

The preapproved-plan program

Every California city was required to run a preapproved-ADU-plan program by January 1, 2025 under AB 1332 (Gov. Code § 65852.27(a)), and Gardena runs one. The City accepts master plan sets for detached ADUs from designers, architects and builders, reviews them against the same standards as any ADU application, and posts the approved plans with the designer’s contact details so homeowners can license them directly. A preapproval stays valid until the City adopts new building codes.

The payoff is the 30-day clock in Gov. Code § 65852.27(b). It applies to a detached ADU application that uses a plan the City preapproved in the current triennial building-code cycle, or a plan identical to one the City already approved in that cycle. The decision is then due in 30 days rather than 60. The statute writes that lane for detached units only, which is also how Gardena runs the program. Every preapproved plan still needs site-specific drawings, studies and engineering on top.

Short-term rental and separate sale

Both are closed. GMC § 18.13.040 C sets a minimum rental term of 31 consecutive days and applies it to the ADU and every other residence on the lot, including the main house. State law backs that floor rather than fighting it: Gov. Code § 66323(e) requires a term longer than 30 days on the mandatory-approval track, and § 66333(g) does the same for a junior ADU.

Separate sale is the more commonly misunderstood one, because two different statutes are involved. GMC § 18.13.040 B bars selling an ADU apart from the house except on the conditions of the nonprofit-conveyance statute, which the ordinance still identifies by a section number SB 477 repealed — one of the numbering problems in HCD’s first finding. The operative statute is Gov. Code § 66341, AB 587’s route: a qualified nonprofit that built the unit may convey it separately to a qualified low- or moderate-income buyer under a recorded tenancy-in-common agreement, and no local opt-in is needed. The condominium route is a different statute, Gov. Code § 66342 under AB 1033, and it does need a local opt-in. Gardena has not adopted one.

Recent state-law changes that apply here

HCD’s second finding also asks the City to fold AB 130, AB 462 and SB 9 into the ordinance as it updates. Those bills are named in the letter without a description of their effect, and this page does not characterize them beyond that. Gardena has no Coastal Zone, no very-high fire hazard severity zone and no historic overlay, which is why this section is about paperwork rather than terrain.