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

Can I build an ADU in Agoura Hills?

Five things to know before you start

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

How many units your lot can take

Everything in this section is grounded in AHMC § 9283.2 and Gov. Code § 66323; we won’t re-cite the local section on every line. The ordinance takes an unusual approach for Los Angeles County: rather than writing its own unit counts, it permits every unit state law describes, ministerially, by reference.

Under Gov. Code § 66323(a)(1)–(2) — confirmed by the HCD ADU Handbook (March 2026), p. 17 — a single-family lot may combine a conversion ADU carved from existing space in the house or an accessory structure, a JADU of up to 500 sqft inside the house, and a new detached ADU of up to 800 sqft with 4-foot setbacks. That is up to two ADUs plus a junior ADU. State law separately requires the City to allow at least one ordinance ADU under Gov. Code § 66314 — the larger unit AHMC § 9283.3 governs.

On a lot with an existing multifamily building, the ordinance again defers to state law, so the SB 1211 counts apply as written: conversion ADUs in non-livable space, at least one and up to 25% of the existing unit count (Gov. Code § 66323(a)(3)(B)), and up to eight detached ADUs, capped at the number of existing units (Gov. Code § 66323(a)(4)(A)(ii)). JADUs are a single-family product only.

Owner-occupancy

You do not have to live on the property to build or rent an ADU. The ordinance says so directly, and Gov. Code § 66315 forbids a city from requiring it. An investment build or a family-flex build works here the same way it does anywhere else in the county.

What an ADU costs in Agoura Hills (2026)

Our Signature plans are fixed-price — architectural design and full permit processing included, the same number whether the lot is in Old Agoura, south of the 101, or in 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.

The two-story models are shown for reference. In Agoura Hills the detached envelope is single story, so the Lincoln at 1,000 sqft is the ceiling as drawn — and it lands exactly on the City’s two-plus-bedroom cap. Custom work is priced per project, $9,990–$19,990 for design and permit processing.

City fees and pass-throughs

A conforming ADU is a ministerial building permit, so there is no planning entitlement fee to pay. Per the City’s Master Fee Schedule effective July 1, 2025, building permits are valuation-based against the current ICC valuation tables: in the $100,001 to $500,000 tier, a base of $2,482.36 plus $11.27 per additional $1,000 of value. Plan check runs 95% of the building permit fee, and the mechanical, electrical, and plumbing trades add roughly 10%, 15%, and 10% of the permit fee respectively.

Several surcharges ride on top and are easy to forget: a General Plan fee of 1.19% of the building permit, a 7% technology fee, a Strong Motion Instrumentation fee of 0.013% of the building permit, and the state’s $1 per $25,000 of valuation building-standards fee. Two ADU-specific planning line items round it out: recording the ADU restrictive covenant is $866, and an administrative zoning clearance is $325. Conversions catch a break — the City values remodel work at a third of new-construction valuation, which pulls every percentage fee down with it.

What it returns: renting your ADU

Long-term rental only. 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 FY 2026, as revised effective May 21, 2026: $2,079 for a studio, $2,328 for a one-bedroom, $2,903 for a two-bedroom, and $3,681 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 Las Virgenes school-district neighborhood typically rents above FMR — we would rather point you at a verifiable number than an invented one. A local property manager can price your specific street.

HUD FMR figures: FY 2026 Fair Market Rents, Los Angeles–Long Beach–Glendale HUD Metro FMR Area, as revised effective May 21, 2026 (huduser.gov). Your ADU’s actual performance depends on finish level, lot, access, and the rental market at the time you lease it. For payback math keyed to your lot, use the ADU ROI calculator or the ADU calculator.

When an ADU isn’t the right move

Not every Agoura Hills property is a good ADU candidate, and it is cheaper to learn that now than after you have paid for plans. Four situations where we would tell you to wait, pick a different unit type, or not build:

• Your numbers depend on short-term rental income. They will not work. AHMC § 61005 bars it outright and the ADU chapter sets a 30-day floor that state law requires. Run the math on a 30-day-plus tenancy or reconsider.
• You want a separate-sale exit. The City has not opted into AB 1033, so the ADU cannot be sold apart from the house. If a condominium-style exit is the plan, this is the wrong jurisdiction for it.
• You need two stories of detached space exactly as our stock plans draw it. The detached envelope is 16 feet. The honest routes are a single-story plan, a modified two-story plan, or a custom design — not a variance, which takes the project out of ministerial review entirely.
• Your only buildable pad is under protected oaks, or your Very High parcel has no wildfire budget. Chapter 7A assemblies and an oak tree permit are both real costs. If the project only pencils without them, a conversion inside an existing structure is usually the better move.

The rules that make Agoura Hills different

Building in a wildfire-mapped city

Agoura Hills sits against the Santa Monica Mountains, and the Woolsey Fire came through this corridor in 2018. When the Office of the State Fire Marshal released the final phase of its Local Responsibility Area Fire Hazard Severity Zone maps on March 24, 2025, much of the city landed in Very High territory. Whether your parcel is mapped Moderate, High, or Very High is a lookup, not a guess — and it is the first thing we check on a Backyard Review here.

The ordinance meets the maps head-on. In a Very High zone a detached ADU must keep a 10-foot separation from other structures on the lot. But the drafters wrote the state floor into the exception: where that separation would preclude an 800-square-foot ADU with 4-foot setbacks, a reduced separation is allowed, with the unit built to the California Building Code’s fire-resistance requirements (AHMC § 9283.3(N)). Even on a tight hillside lot, the 800-square-foot unit stays buildable.

Old Agoura, equestrian lots, and the 800-square-foot floor

This is not a uniform grid of a city. Old Agoura keeps its rural, horse-keeping character under a design overlay; the newer neighborhoods south of the 101 climb toward the mountains on sloped, oak-studded lots. Ordinance No. 25-481 deals with both, and the state’s 800-square-foot floor is the thread tying the answers together.

In the Old Agoura Design Overlay a detached ADU may occupy up to 25% of the required front yard — a genuinely useful allowance on deep rural lots where the buildable rear yard is taken up by corrals or grade. On equestrian-zoned parcels the community development director may waive the minimum horse-keeping area for lots under 10,890 square feet or with an average slope over 25%, so the ADU and the horses are not competing for the same flat pad.

Underneath both overlays sits the guarantee at AHMC § 9283.3(K): no matter what the lot-coverage, front-setback, or horse-keeping math says, one 800-square-foot ADU at 16 feet with 4-foot side and rear setbacks must be allowed on the lot (Gov. Code § 66321(b)(3)).

Oak trees

Agoura Hills runs an oak-preservation program, and work near a protected oak takes an oak tree permit with planning review and, where trees are removed, consultant review. It is a real line item and a real scheduling item. Worth an arborist walk before you place the unit rather than after.

A December 2025 ordinance, written to the current code

The regulatory picture here is unusually clean. Ordinance No. 25-481 repealed and replaced the ADU chapter in full, drafted to the renumbered Government Code, after several years of correspondence with the state Department of Housing and Community Development — the registry lists letters dated February 3, 2023, May 7, 2025, and October 6, 2025. The rules on this page are not a decade-old chapter propped up by preemption arguments. The full § 66323 stack is codified by direct reference, there is no owner-occupancy requirement for an ADU, and the 800-square-foot state floor is written into the ordinance’s own text twice.

Two gaps survive. The JADU owner-occupancy clause states the pre-AB 1154 rule, as covered above. And the JADU definition at AHMC § 9120 places a JADU within the single-family residence while excluding the attached garage — state law is broader, allowing a JADU within the walls of the existing or proposed single-family dwelling, attached garage included (Gov. Code § 66323(a)(1); § 66333). A garage-conversion JADU application should cite the statute, not the local definition.

No separate-sale path

Ordinance No. 25-481 kept the prohibition on selling an ADU or JADU separately from the primary residence, apart from the narrow nonprofit path in Gov. Code § 66341. The City has not adopted an AB 1033 condominium opt-in (Gov. Code § 66342). Among LA-area cities only a handful have — Santa Monica (SMMC § 9.31.026, 2025) and Culver City (CCMC § 17.400.096, 2026) among them. Build here for rental income, family housing, or long-term value.