Building an ADU in Westlake Village. Rules, costs, timeline.

Can I build an ADU in Westlake Village?

Five things to know before you start

If you read nothing else on this page, read these. They are the five points that change the most Westlake Village projects.

First, confirm which city’s rules apply to you

This is not a technicality here, and it is the one jurisdiction check we would run before any other. “Westlake Village” is both a city in Los Angeles County and a postal name that covers a much larger area straddling the Ventura County line. The City puts the warning in its own application instructions: many properties have a Westlake Village mailing address but are not located in the City. In our experience the two usual answers are the City of Thousand Oaks, in Ventura County, and unincorporated Los Angeles County — and each writes its own ADU rules, so nothing on this page would govern your project. Run your address through the City’s Zoning and Neighborhood Finder first. It takes a minute and it has saved more than one homeowner a wasted set of plans.

Which lots the ordinance covers

WLVMC § 9.14.070(A) permits ADUs in the R-1 and RPD zones and in the Mixed Use Lindero and Mixed Use Corsa districts of the North Business Park Specific Plan. It also requires the ADU to sit on the same lot as an existing or proposed detached primary residence. Read literally, that last clause would shut out a lot whose primary dwelling is attached — a condition state law does not impose. Gov. Code § 66323(a) requires ministerial approval of qualifying units in any residential or mixed-use zone, and § 66314(a) limits the grounds for designating where ADUs may go to water and sewer capacity and to traffic and public safety. If your primary dwelling is attached, do not treat the local wording as the end of the conversation.

How many units your lot can take

Everything in this section is grounded in WLVMC § 9.14.080 and Gov. Code § 66323; we won’t re-cite the local section on every line. Read alone, the local text is narrow. Its building-permit-only track allows one ADU and one JADU created inside the existing or proposed space of the house or an existing accessory structure, or one new detached ADU of up to 800 square feet that “may be combined with” that JADU. On a plain reading you get one ADU and one junior unit.

State law is more generous, and it is the operative rule. Gov. Code § 66323(a)(1)–(2) requires a local agency to allow those categories in combination, and the HCD ADU Handbook (March 2026, p. 17) puts it in plain words: local agencies must allow at least one ADU constructed from existing space, one JADU, and one newly constructed detached ADU. That is up to two ADUs plus a junior ADU on a single-family lot — a conversion carved out of the house or the garage, a junior unit inside the house, and a new detached building of up to 800 square feet with four-foot setbacks.

On a lot with an existing multifamily building, the ordinance allows conversion ADUs in non-livable space up to 25 percent of the existing units, and caps detached ADUs at two. State law allows up to eight detached ADUs on a lot with an existing multifamily dwelling, not exceeding the number of existing units (Gov. Code § 66323(a)(4)(A)(ii); Handbook p. 17). The local cap of two is the pre-SB 1211 number.

Owner-occupancy

You do not have to live on the property to build or rent an ADU. The covenant the City requires you to record says otherwise for any ADU permitted after January 1, 2025 — but that provision was drafted against a sunset date that no longer exists. Gov. Code § 66315 bars a local agency from requiring owner-occupancy for an ADU, full stop, and AB 976 removed the 2025 expiry the local text was written around. The junior ADU is the real exception, and a narrower one than the ordinance suggests: WLVMC §§ 9.14.080(E)(6) and (F)(3) require an owner to occupy one of the units on the lot, while AB 1154 — effective January 1, 2026, amending Gov. Code § 66333 — limits that requirement to a JADU that shares sanitation facilities with the primary home. Give the junior unit its own bathroom and the state rule controls.

What an ADU costs in Westlake Village (2026)

Our Signature plans are fixed-price — architectural design and full permit processing included, the same number whether the lot is in Westlake Village, the South Bay or the east 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:

In Westlake Village the two-story models and the 1,080–1,200 sqft plans are shown for reference: the detached envelope here is single story and 1,000 sqft, so the Lincoln is the ceiling as drawn. Custom work is priced per project, $9,990–$19,990 for design and permit processing.

City fees and pass-throughs

The City’s side is unusually cheap. A Zoning Clearance application costs $50. The larger numbers come from the County of Los Angeles, which issues the building permit and charges valuation-based permit and plan-check fees. The ordinance also puts sewer, water, school district and other applicable fees on the owner, development impact fees included. It requires a new or separate utility connection too, with its connection fee or capacity charge, unless the unit is exempt (WLVMC § 9.14.070(B)(10)).

Several state-law protections cut into that list, and the ordinance restates none of them. An ADU of 750 square feet or less is exempt from development impact fees entirely (Gov. Code § 66311.5(c)(1)); above that, the fee must be proportional to the primary dwelling rather than charged at a flat new-home rate. A unit under 500 square feet of interior livable space does not increase assessable space, so it owes no school impact fees (§ 66311.5(c)(3)) — which covers the Wilshire at 400 square feet.

The utility rules are more specific than the ordinance suggests. For a § 66323(a)(1) unit — a conversion ADU or a JADU — the City may not require a new or separate utility connection and may not charge a connection fee or capacity charge at all (Gov. Code § 66311.5(d)). For other ADUs the charge must be proportionate (§ 66311.5(e)), and an ADU is not treated as a new residential use unless it was built together with a new single-family dwelling (§ 66311.5(b)). If your lot is on a private sewage disposal system, the County health officer has to approve it, so start that review early.

What it returns: renting your ADU

Long-term only. The covenant recorded against the property bars renting the unit for less than 30 consecutive days, and state law requires the same floor for § 66323 units (Gov. Code § 66323(e); § 66333(g) for JADUs). 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 Westlake Village. 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 inside the Las Virgenes Unified School District typically rents well 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: revised FY 2026 Fair Market Rents, Los Angeles–Long Beach–Glendale HUD Metro FMR Area, effective May 21, 2026 (91 FR 21301, Apr. 21, 2026; huduser.gov). Your specific ADU’s 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 Westlake Village 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, choose a different unit type, or not build:

• Your address is not in the City. If the Zoning and Neighborhood Finder puts you outside the city limits, none of these numbers are yours. Get the jurisdiction right before anything else — the rules differ.
• Your numbers depend on short-term rental income. They will not work. The 30-day minimum is recorded against the title as a covenant and has no ADU carve-out. Run the math on a 30-plus day tenancy or reconsider.
• You want a separate-sale exit. The City has not opted into AB 1033, and the covenant bars separate sale outright. If a condominium 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, an attached two-story design, or a custom unit — not a variance, which takes the project out of ministerial review entirely.

The rules that make Westlake Village different

The HOA question

Westlake Village is a master-planned city. Most of its residential neighborhoods sit inside a homeowners association, and the City’s Zoning Clearance instructions tell residential applicants to obtain approval from their association and to upload proof of it with the application. For most projects — a patio cover, a repaint — that is unremarkable. For an ADU it collides with state law.

California treats an ADU permit as ministerial. The agency checks the plans against objective standards, then approves or denies. Gov. Code § 66317(c) says no other local ordinance, policy or regulation may be the basis for the delay or denial of an ADU permit — delay counts. Section 66315 bars additional standards, and § 66316 makes ministerial review mandatory and renders a noncompliant local ordinance null and void. HCD is blunt about what that means for associations. An HOA may not influence a local agency’s ministerial approval of an ADU or JADU. If a local agency lets an HOA into any part of the application process, the agency is in violation of State ADU Law (HCD ADU Handbook, March 2026, p. 26).

Two Civil Code sections go further. Section 4751 voids any covenant or restriction in a common interest development that effectively bars an ADU or JADU, or unreasonably restricts one, on a lot zoned for single-family use. Section 714.3(b) adds the part that matters at the board meeting: the “reasonable” restrictions an association may still impose shall not include any fees or other financial requirements.

What we actually advise: engage your board early and in good faith. An association that has seen the drawings, understands the roof pitch matches, and knows the unit is single-story is a faster path than a correct legal argument. But go in knowing that a “no” from the board is not a “no” from the City, and that the association may not attach a fee to the review (Civil Code § 714.3(b)).

The Very High Fire Hazard Severity Zone

Parts of the city sit against the Santa Monica Mountains, and the ordinance treats a lot inside the General Plan’s Very High Fire Hazard Severity Zone differently. WLVMC § 9.14.080(D) permits no ADU or JADU on such a property unless three conditions are met: no more than one ADU or one JADU on the property, compliance with applicable brush clearance requirements, and fire sprinklers in the new unit where the primary dwelling requires them.

Two of those three survive state law comfortably. Brush clearance and sprinkler parity are fire-safety standards, and state law leaves those to the fire code. Note that the sprinkler condition is parity, not a trigger: an ADU does not need sprinklers where they are not required for the primary dwelling (Gov. Code § 66314(d)(12)). The ordinance opens that clause with “unless otherwise required by applicable City building and fire codes,” so confirm the current fire-code position on a new detached unit inside the zone. The one-unit cap is different. It is a count limit, not a fire-safety standard, and it cuts into the combination Gov. Code § 66323 guarantees. Where a local rule is narrower than state law, state law controls (Gov. Code § 66316). Confirm your parcel’s designation before you design to either reading — the General Plan map decides it, not the street.

Where the ordinance trails current state law

WLVMC §§ 9.14.070 and 9.14.080 were last amended by Ordinance No. 297-22 in December 2022. Three state-law changes have landed since, and the text still cites the old Gov. Code § 65852.2 numbering that SB 477 replaced with §§ 66310–66342 in March 2024. On the envelope — size, height, setbacks, parking — the ordinance holds up well. On counts and covenants it does not.

This is not only our reading. On February 27, 2026, HCD’s Housing Accountability Unit wrote to the City’s Planning Director. Its Letter of Technical Assistance notes that the most recent Westlake Village ADU ordinance on file is from 2022, warns that it may therefore be outdated and out of compliance with State ADU Law, and lists the changes it predates. HCD asked for a reply by March 29, 2026. Where a local ordinance is noncompliant, state law applies until the city fixes it (Gov. Code §§ 66316, 66326). Ask the Planning Department where that stands before you lean on the local text either way.

No separate-sale path

A Westlake Village ADU stays on the same title as the house. The covenant required by WLVMC § 9.14.080(F)(1) prohibits selling, transferring or assigning the unit separately from the primary residence, and separate condominium sale is only available where a city has opted in under AB 1033 (Gov. Code § 66342). Westlake Village has not, and only a handful of California cities have opted in at all. Build here for rental income, family housing or long-term property value, not for a condominium exit.

Short-term rental

Off the table, and enforced through the title rather than a code section you could argue about. Within thirty days of the building permit being issued, the owner records a covenant with the Los Angeles County Registrar-Recorder that runs with the land and binds every future owner. Among its terms: the ADU or JADU may not be rented for a period of less than thirty days. State law points the same way for § 66323 units (Gov. Code § 66323(e)). If your investment case needs nightly rates, it does not survive first contact with the covenant.