Building an ADU in Agoura Hills. Rules, costs, timeline.

What you can build: size, height, and setbacks

Everything in this section comes from AHMC § 9283.3 — the track that governs a standard, non-exempt ADU — with state-law citations called out where the statute preempts or supplements the local rule. We won’t re-cite the local section on every line; assume it under each subsection unless we say otherwise. The state-exempt track is covered in the next section.

Size limits

A new detached ADU may reach 850 square feet as a studio or one-bedroom, or 1,000 square feet with two or more bedrooms. Those are the exact minimums state law requires a city to allow (Gov. Code § 66321(b)(2)) — Agoura Hills sits on the floor, with no local headroom above it. A new attached ADU carries the same caps plus a second limit: no more than 50 percent of the main house’s living area, whichever is less. State law puts a hard bottom under that percentage: it may not restrict an attached ADU below 850 square feet for a studio or one-bedroom, or 1,000 square feet with two or more bedrooms (Gov. Code § 66321(b)(2); HCD ADU Handbook, pp. 38–39). On a smaller house — say 1,600 square feet, where 50 percent computes to 800 — the “whichever is less” prong is preempted and the 850/1,000 floors control. A JADU is capped at 500 square feet (Gov. Code § 66313(d)).

Conversions get more room. A legally established accessory structure converted to an ADU may occupy the structure’s full floor area, whatever it measures. Expand beyond the existing footprint and the expansion is capped at 1,000 square feet total.

Setbacks

Side and rear setbacks are 4 feet — exactly the state-law floor in Gov. Code § 66314(d)(7), and a city may not require more for a conforming ADU. The front setback follows the underlying zone for the primary residence, with two carve-outs worth knowing. In the Old Agoura Design Overlay, a detached ADU may occupy up to a quarter of the required front yard. And no setback at all applies to an in-place, in-kind conversion of an existing structure.

One placement rule is specific to this ordinance: a detached ADU keeps a 10-foot separation from the primary dwelling. On most Agoura Hills lots that is easy to hold. Where it isn’t, note that a § 66323 unit — the 800-square-foot detached path covered in the next section — is subject only to the standards in § 66323 itself (Gov. Code § 66323(b); HCD ADU Handbook, pp. 16, 19), so the separation rule cannot be used to block that unit — though in a mapped fire zone the building code’s fire-resistance rules still apply on their own terms.

Maximum height

A new detached ADU may not exceed 16 feet, measured to the roof peak above grade — the state-law floor in Gov. Code § 66321(b)(4)(A). The ordinance expressly allows up to 18 feet where state law grants it, such as within a half-mile walking distance of a major transit stop or high-quality transit corridor, plus 2 more feet to carry a roof pitch matching the main house (Gov. Code § 66321(b)(4)(B)). A new attached ADU may reach the lesser of the zone’s height limit for the primary dwelling or 25 feet, matching Gov. Code § 66321(b)(4)(D).

What that means for design: Agoura Hills is a single-story detached-ADU market. Our three two-story Signature Homes are detached-only products that need roughly a 25-foot detached envelope to permit, so they sit out on Agoura Hills lots. The 25-foot allowance here applies to attached ADUs, and we don’t sell the two-story plans as attached units. Our six single-story plans are all designed to sit at or under 16 feet — and on the wide, deep lots this city is known for, spreading out costs less than building up anyway.

Parking

The baseline is one off-street space per ADU, and tandem parking on an existing driveway counts. The exemptions in Gov. Code § 66322(a) apply on top — among them transit proximity, a historic district, an ADU created within an existing primary or accessory structure, an on-street permit area where the ADU occupant isn’t offered a permit, and car-share proximity.

Three rules cut in your favor regardless of that list. Demolishing or converting a garage, carport, or covered space to build the ADU never triggers replacement parking — the ordinance says so expressly, tracking Gov. Code § 66314(d)(11). A JADU requires no parking at all (Gov. Code § 66334(a)). And no parking may be required for any § 66323 unit, including the 800-square-foot detached path (Gov. Code § 66323(b); HCD ADU Handbook, p. 33).

Lot coverage and the design standards

A standard ADU must conform to the zone’s lot-coverage limit, and on a hillside or equestrian parcel other overlay standards can bind first. The ordinance builds in the state-law release valve: notwithstanding lot coverage, front setbacks, or minimum horse-keeping areas, one 800-square-foot ADU at 16 feet with 4-foot side and rear setbacks must be allowed on any lot (Gov. Code § 66321(b)(3)). The next section covers what else that unit escapes.

Design standards for a standard ADU are objective and short: exterior materials, colors, and finishes match the primary dwelling; exterior lighting is shielded and directed downward; an attached ADU gets its own exterior entrance and no internal connection to the main house; and every unit sits on a permanent foundation built to the residential code.

Owner-occupancy

Owner-occupancy is not required for an ADU — the ordinance says so directly, and state law forbids requiring it (Gov. Code § 66315). You can build the unit and rent it whether or not you live on the property.

JADUs are where the ordinance shows its adoption date. AHMC § 9283.2(E) requires the owner to reside in either the JADU or the remaining portion of the house, and subsection (F) records that condition in a deed restriction. That text states the rule as it stood before January 1, 2026. AB 1154 amended Gov. Code § 66333(b), effective that date, so JADU owner-occupancy can only be required where the JADU shares sanitation facilities with the primary dwelling. A JADU with its own bathroom falls outside the rule entirely — and because the ordinance took effect after AB 1154 did, the broader local language is preempted from day one.

Impact fees and utilities

An ADU of 750 square feet or less pays no development impact fees statewide (Gov. Code § 66311.5(c)(1)), and the ordinance repeats the exemption in both of its tracks. Above 750 square feet, impact fees must be proportional to the primary dwelling’s size — never a flat per-unit charge.

Utilities differ by track, and the difference is real money (AHMC §§ 9283.2(G), 9283.3(O)). A state-exempt unit — a conversion, a JADU, or the 800-square-foot detached path — cannot be required to take a new or separate utility connection, unless the ADU is built together with a brand-new house. For the detached unit that is the ordinance’s own grant, and a generous one: state law only compels the exemption for conversions and JADUs, and would otherwise let a city require a connection for new construction (Gov. Code § 66311.5(d)–(e)). A standard new-construction ADU under § 9283.3 is the opposite: the ordinance requires a new, separate sewer connection, with a connection fee or capacity charge proportionate to the unit — sized by interior livable area or drainage fixture units and capped at the reasonable cost of providing the service. If your lot runs on a private sewage system instead, the environmental health officer signs off first.

Permitting timeline

A conforming ADU is approved ministerially by the community development director — building permits only, no discretionary review, no hearing, no neighbor sign-off (AHMC § 9283.1; Gov. Code § 66317). The City must act on a complete application within 60 days, and a denial must come with a written list of every defect and how to fix it. Miss the 60 days and the application is deemed approved under state law. One quirk: if you’re building the ADU together with a new house, the City may defer the ADU decision until it acts on the primary dwelling — the review stays ministerial either way.

How California state law overrides Agoura Hills

Ordinance No. 25-481 was written under HCD’s eye, so the remaining gaps are few — but they exist, and they matter to real projects. Three are worth knowing before you draw anything.

• JADU owner-occupancy. AHMC § 9283.2(E) requires the owner to live in the JADU or the remaining portion of the house, and subsection (F) bakes that into a recorded deed restriction. AB 1154 narrowed the state rule effective January 1, 2026: owner-occupancy may only be required where the JADU shares sanitation facilities with the primary dwelling (Gov. Code § 66333(b)). For a JADU with its own bathroom, the local requirement — and that clause of the covenant — is preempted.
• Where a JADU can go. The definition in AHMC § 9120 places a JADU within the single-family residence but excludes the attached garage. State law is broader: a JADU may be built within the walls of the existing or proposed single-family dwelling, and HCD reads that to include an attached garage (Gov. Code § 66333; HCD ADU Handbook). A garage-conversion JADU application should cite the statute, not the local definition.
• Multifamily detached counts. The ordinance handles multifamily lots by reference to § 66323 rather than by its own numbers — which means the SB 1211 floors apply as written: conversion ADUs in non-livable space up to 25 percent of the existing unit count, and up to eight detached ADUs on a lot with an existing multifamily dwelling, capped at the number of existing units (Gov. Code § 66323(a)(3)–(4)). Nothing in the local text may be read to narrow those counts.

Two more state floors sit quietly underneath the ordinance. Fire sprinklers are not required in an ADU if the primary residence does not have them — the ordinance repeats this in both tracks (Gov. Code § 66314(d)(12)). And an unpermitted unit built before January 1, 2020 has a streamlined legalization pathway under AB 2533 (Gov. Code § 66311.7, renumbered from § 66332 by 2025 legislation).

The ADU permit process, step by step

Agoura Hills runs building and planning permits through the MGO Connect online portal — application, plan check, fee payment, and permit issuance all happen there. Because a conforming ADU is ministerial, there is no planning entitlement to win first. The path is a building permit and its trade permits, reviewed by the community development director against objective standards.

The honest timeline for a Signature plan looks like this. Plan preparation runs about two weeks — the plan is pre-engineered and gets customized to your lot rather than drawn from scratch. Once submitted, the City must determine completeness and notify you in writing within 15 business days (SB 543, effective January 1, 2026; Gov. Code § 66317(a)(2)(A)) — and if it misses that notice, the application is deemed complete (Gov. Code § 66317(a)(2)(F)). From a complete application, the City has 60 days to approve or deny, and the project is deemed approved if that clock runs out (Gov. Code § 66317(a)). Pre-engineered plans clear plan check in weeks rather than months, because the reviewer is checking conformance rather than evaluating a novel design. Construction then runs four to six months by model size — roughly four months under 600 square feet, five from 600 to 800, six above 800 — and that is the phase we guarantee in writing, with a daily delay penalty if the contracted finish date is missed.

Start to finish, that is about six to nine months for a Signature plan. Custom designs run longer on both ends: bespoke design time up front, and a slower plan check because the City is seeing the drawings for the first time.

Three Agoura Hills-specific items to plan for, none of them exotic:

• Fire-zone plan detailing. On a Very High parcel, the plan set carries Chapter 7A assemblies and the § 9283.3(N) separation logic from the first sheet. Retrofitting a set drawn for a non-wildfire jurisdiction costs review cycles.
• Grading and sewer. Sloped lots south of the 101 may need a separate grading permit — the City prices grading plan check and permits by cubic yard on its fee schedule. A standard new-construction ADU also takes a new, separate sewer connection with a proportionate fee; the 800-square-foot § 66323 path does not.
• Oak trees. Protected oaks near the build site mean an oak tree permit and an arborist — sequence it before plan check, not during.

The City also runs a Pre-Approved Standard ADU Plan Program — three pre-reviewed, code-compliant plan sets residents can download at no charge, the local answer to the state’s pre-approval mandate (Gov. Code § 65852.27). Pre-approved plans shorten plan check but fix the design; our Signature plans are permit-ready in the same way while giving you nine layouts and a finish palette to choose from.

Renting out your new ADU

Long-term rental only. AHMC § 61005 bars ADUs, JADUs, and SB 9 units from operating as short-term rentals, and the ADU chapter separately requires any rental to run 30 days or longer — the strictest limit state law lets a city impose (Gov. Code §§ 66323(e), 66333(g)). Month-to-month and annual leases are untouched; short-stay platforms are off the table. If short-term income was the plan, this is the rule that changes it.

For a rent benchmark, the government figure is HUD’s Fair Market Rent for the Los Angeles-Long Beach-Glendale HUD Metro FMR Area, which covers Agoura Hills. For FY2026, effective October 1, 2025, FMR is $1,863 for a one-bedroom, $2,085 for a two-bedroom, and $2,601 for a three-bedroom. Those are metro-wide figures spanning the full range of housing stock and unit ages, so treat them as a floor rather than a forecast — a newly built detached ADU in a high-value Conejo Valley neighborhood typically rents above FMR, and we’d rather point you at a verifiable number than an invented one. A local property manager can price your specific street.

Two structural points in this city’s favor. There is no owner-occupancy requirement for an ADU, so the unit can be rented whether or not you live on site. And the tenant pool here is steady — families near the Las Virgenes schools, professionals working the 101 tech-and-entertainment corridor, and parents downsizing without leaving the neighborhood.