Building an ADU in La Cañada Flintridge. Rules, costs, timeline.

Up to two ADUs plus a junior ADU. LCFMC § 11.33.040(C)(2) allows one JADU inside the house or an accessory structure, one ADU converted from existing space in the house or an accessory structure, and one new-construction detached ADU on the same single-family parcel. That is the full state-law stack in Gov. Code § 66323(a)(1)–(2), confirmed by the HCD ADU Handbook (March 2026, p. 17).

State law separately requires the City to allow at least one ordinance ADU under Gov. Code § 66314 in addition to that stack (HCD ADU Handbook, p. 18), and Ordinance No. 519 is silent on that fourth unit. Separately, the summary table on the City’s ADU web page describes a narrower combination than the ordinance does — the adopted ordinance text is the operative rule.

Per LCFMC § 11.33.060(A)(3), a new detached or attached ADU may reach 1,200 square feet — well above the state floor, which only requires a city to permit 850 square feet for a studio or one-bedroom and 1,000 square feet with two or more bedrooms (Gov. Code § 66321(b)(2)). An attached ADU carries a second limit: no more than 50% of the main house’s floor area.

A legally built existing detached structure converted to an ADU may exceed 1,200 square feet, and may add up to 150 square feet beyond its original footprint for ingress and egress (LCFMC § 11.33.070(A); Gov. Code § 66323(a)(1)). A JADU is capped at 500 square feet (Gov. Code § 66313(d)).

Sixteen feet to the peak on a standard single-family lot, per LCFMC § 11.33.060(C)(1)(b) — the state-law floor in Gov. Code § 66321(b)(4)(A). Within a half-mile walking distance of a major transit stop or a high-quality transit corridor, the cap rises to 18 feet, plus 2 more feet to carry a roof pitch that matches the main house (Gov. Code § 66321(b)(4)(B)). On a lot with a multifamily dwelling the detached cap is 18 feet.

Attached ADUs may reach 25 feet, or the zone’s height limit for the primary dwelling if that limit is lower, and are never required to exceed two stories (Gov. Code § 66321(b)(4)(D)). LCFMC § 11.33.060(C)(1)(a) conditions the 25 feet on the primary home being single-story; state law sets the test by the zone’s height limit, not by the number of stories on the existing house, so that local condition is preempted.

Often not. LCFMC § 11.33.060(E)(1) starts with one on-site space per ADU, sized 10 by 20 feet. Subsection (E)(2) then waives it in six situations. The ADU sits within a half-mile walking distance of public transit. It is inside a historic district. It is created within an existing home or an existing accessory structure. On-street permits are required but not offered to the ADU occupant. A car-share stop is within one block. Or the ADU is permitted alongside a new primary dwelling. That list tracks Gov. Code § 66322.

Separately, and regardless of that list, no parking may be required on a § 66323 unit — a new detached unit of 800 square feet or less, a conversion ADU, or a JADU (Gov. Code § 66323(b); HCD ADU Handbook, p. 33). Demolishing or converting a garage never triggers replacement parking (LCFMC § 11.33.060(E)(3); Gov. Code § 66314(d)(11)), and a city may not require parking for a JADU at all (Gov. Code § 66334(a)).

No. LCFMC chapter 11.33, as replaced by Ordinance No. 519 in February 2024, contains no owner-occupancy requirement for an ADU or a JADU. Under state law a city may never impose owner-occupancy on an ADU (Gov. Code § 66315).

For JADUs, AB 1154 amended Gov. Code § 66333(b) effective January 1, 2026 so owner-occupancy may only be required where the JADU shares sanitation facilities with the primary dwelling. A JADU with its own bathroom falls outside the rule entirely.

Usually yes — with one exception worth real money. LCFMC § 11.33.060(F)(1) requires a new-construction ADU to match the primary dwelling’s roof pitch, window size, proportion of window units to wall area, direction of window openings, muntin pattern, exterior building materials, lighting fixtures, and paint colors. But subsection (F) opens by applying those standards to ADUs “with the exception of Statewide Exempt ADUs” — defined at LCFMC § 11.33.030 as a new detached unit of 800 square feet or less, at least 4 feet from side and rear lot lines, with a peak height of 16 feet or less. Build inside that envelope and the whole matching list drops away.

Two extensions come from state law rather than the ordinance. The height ceiling for that unit is 16, 18, or 20 feet depending on the conditions in Gov. Code § 66321(b)(4), not a flat 16 (Gov. Code § 66323(a)(2)(B); HCD ADU Handbook, p. 16). And a conversion ADU and a JADU are § 66323 units too, so local design standards may not be imposed on them either (Gov. Code § 66323(b); HCD ADU Handbook, pp. 16, 18).

The entire city is mapped Very High on the CAL FIRE and Office of the State Fire Marshal Local Responsibility Area fire hazard severity zone map dated March 24, 2025, which the City publishes on its own site. Every new ADU is therefore built to California Building Code Chapter 7A ignition-resistant standards — rated exterior wall and roof assemblies, ember-resistant vents, tempered or multi-pane glazing, and non-combustible eave and deck detailing — and the lot must carry defensible space under Gov. Code § 51182, the Local Responsibility Area defensible-space statute.

Fire-zone status is not a basis to deny an ADU. Fire sprinklers are a separate question: an ADU needs them only if the primary residence already requires them (LCFMC § 11.33.050(C); Gov. Code § 66314(d)(12)).

No. LCFMC § 11.33.050(G) bars renting an ADU for any term shorter than 30 days.

That is not a local choice: Gov. Code § 66323(e) requires a local agency to impose a rental term longer than 30 days on a § 66323 unit, and Gov. Code § 66333(g) does the same for JADUs. Month-to-month and annual leases are unaffected. If nightly income was the plan, this is the rule that changes it.

No. LCFMC § 11.33.050(D) prohibits conveying an ADU or JADU separately from the lot and the primary dwelling, apart from the narrow state-law path for units built or developed by a qualified nonprofit (Gov. Code § 66341).

AB 1033 lets a city adopt a local ordinance allowing condominium-style separate sale (Gov. Code § 66342), and La Cañada Flintridge has not adopted that opt-in — Ordinance No. 519 kept the prohibition. Build here for rental income, family housing, or long-term value, not for a condominium exit.

Yes, and it is often the shortest road to a permit. Per LCFMC § 11.33.070, a legally built existing structure may be converted to an ADU, or demolished and rebuilt in the same location to the same dimensions, with up to 150 square feet of expansion for ingress and egress. No setback is required for that conversion, provided the original side and rear setbacks satisfy the fire agency, and no parking is required.

Demolishing or converting a garage never triggers replacement parking (Gov. Code § 66314(d)(11)), and the City issues the demolition permit concurrently with the ADU building permit (LCFMC § 11.33.050(J)). A conversion carried out under Gov. Code § 66323(a)(1) has no square-foot cap at all.

The City must approve or deny a complete ADU application within 60 days where a dwelling already exists on the lot, and the review is ministerial — no hearing, no discretionary design review (LCFMC § 11.33.040(A)–(B); Gov. Code § 66317(a)). A denial must arrive with a full written list of what is deficient and how to remedy it. The City must also determine completeness and notify you in writing within 15 business days (SB 543, effective January 1, 2026; Gov. Code § 66317(a)(2)(A)); if it misses that notice the application is deemed complete (Gov. Code § 66317(a)(2)(F); HCD ADU Handbook, p. 35).

On a pre-engineered Signature plan, expect roughly 2 weeks of plan preparation, a permit cycle measured in weeks rather than months, then 4 to 6 months of construction — about 6 to 9 months start to finish. Custom designs run longer on both ends.

Signature plan fees are fixed at $7,490 to $12,990, which includes architectural design and full permit processing. Building the unit with an independent licensed general contractor is estimated at roughly $180K–$420K across the lineup, depending on size.

City fees are separate. Per the City’s Master Fee Schedule, there is no separate ADU planning entitlement fee; building permit and plan check follow the adopted Los Angeles County Building Code tables at Exhibit “C” and are valuation-based, with a General Plan Maintenance surcharge of 5% of building permit fees, a State Green Building fee of $1 per $25,000 of valuation, and a Strong Motion Instrumentation fee of 0.00013 times valuation on top. Two local extras matter on this terrain: Chapter 7A wildfire assemblies and, on sloped parcels, grading and retaining work.

Not below 750 square feet. An ADU of 750 square feet or less pays no development impact fees anywhere in California (Gov. Code § 66311.5(c)(1)), and La Cañada Flintridge does not set a different threshold. Above 750 square feet, impact fees must be charged proportionally to the primary dwelling’s size rather than flat per unit.

A JADU of 500 square feet or less is exempt as well, and an ADU or JADU under 500 square feet is not subject to school impact fees (Gov. Code §§ 66311.5, 66311.5(c)(3)); school fees may otherwise apply by unit size and district. Utility connection fees and capacity charges are a separate item, and an ADU may not be treated as a new residential use for that purpose unless it is built concurrently with a new single-family home (Gov. Code § 66311.5(d); HCD ADU Handbook, p. 22).

Yes. The City runs a pre-approved detached ADU program — two-bedroom Craftsman designs at 748 and roughly 799 square feet, prepared by an outside architect — which is the local answer to the statewide pre-approval mandate of AB 1332 (Gov. Code § 65852.27, program required to be in place by January 1, 2025).

A pre-approved plan moves faster through the counter but is built as filed. CALI ADU does not participate in the program: our Signature plans are individually permitted on your lot and adapted to its grade, setbacks, tree canopy, and wildfire exposure.

It reduces the total floor and roofed area your parcel is allowed, and on a foothill lot with a large existing house it usually binds before the ADU size cap does. LCFMC chapter 11.11 sets a total floor and roofed area for the parcel and chapter 11.35 applies a slope factor that shrinks it as the lot gets steeper; an ADU counts against that budget like any other structure (LCFMC § 11.33.060(A)(1)).

The ordinance builds in two answers. Where those rules would block an 800-square-foot ADU, one Statewide Exempt ADU is permitted anyway (LCFMC § 11.33.060(A)(1)(a)). And a permit application for a new house that already maximizes the parcel budget may include an additional 800 square feet within the design to accommodate one (LCFMC § 11.33.040(B)(2)(a)). Both rest on Gov. Code § 66321(b)(3), which forbids using floor-area ratio, lot coverage, or open-space standards to prevent an 800-square-foot ADU.