ADU rules in Simi Valley

Detached ADUs are a permitted use in every residential and open space zone (OS, RE, RVL, RL, RM, RMod, RH, RVH and MH) and in the Mixed-Use Overlay, approved ministerially under SVMC 9-44.160 as restated by Ord. 1373 (effective 8-27-2026). The ordinance sorts them into Class 2-s, the state-exempt unit of up to 800 sq ft under Gov. Code 66323 (4-ft side and rear setbacks, no front setback, no parking), and Class 2, a local-track unit of up to 1,000 or 1,200 sq ft that keeps a 20-ft front setback, a 6-ft separation and design rules; on multifamily lots Class 6-s detached units come in the numbers 66323(a)(4) sets (up to eight beside an existing building but no more than its unit count, or two with a proposed building). On lots subject to the Hillside Performance Standards (Chapter 9-32) only 66323 units are allowed, so a detached ADU there is capped at 800 sq ft. Section C allows every combination 66323(a) authorizes; staff told the Planning Commission on 4-8-2026 that a lot can pair one state-exempt and one local-track detached ADU but not two state-exempt ones, and HCD's 9-1-2026 findings require the city to allow at least one 66314 unit alongside the 66323 units.

Attached ADUs are allowed in the same zones: Class 3 is a newly built addition sharing at least 10 ft of wall with the primary dwelling, Class 4-sp is a conversion inside the existing or proposed primary dwelling (plus up to 150 sq ft for ingress and egress), and Class 4-sa converts an existing accessory structure. JADUs (Class 1-s, up to 500 sq ft inside an existing or proposed single-family home) remain permitted in OS, RE, RVL, RL, RM and RMod, but Ord. 1373 switched them off in the RH and RVH zones (MH already barred them) because Gov. Code 66333 confines JADUs to single-family dwellings; on multifamily lots Class 5-s conversions of non-livable space (at least one, up to 25 percent of the existing units under 66323(a)(3)) take their place. On hillside-standard lots only state-exempt units are allowed, which rules out a new-construction attached addition there but not an internal conversion or a JADU.

Ord. 1373 caps a state-exempt detached ADU (Class 2-s) at 800 sq ft and a local-track detached ADU (Class 2) at 1,000 sq ft on lots up to 8,000 sq ft and 1,200 sq ft on larger lots; an attached ADU (Class 3) may be 850 sq ft, or 50 percent of the primary dwelling up to 1,000 sq ft where that is larger, with garages and patios excluded from the home's square footage. Conversions inside existing space and multifamily units carry no stated cap, JADUs stop at 500 sq ft, and on hillside-standard lots the 800 sq ft exempt unit is the only detached option. Detached units are one story and 18 ft (20 ft near major transit to match the main roof pitch), attached units two stories and 25 ft or the zone limit (up to 30 ft with 10-ft side and 20-ft front and rear setbacks). Local-track detached units also face lot-coverage limits (no more than 40 percent of the first 10 ft of a side yard and of the 20-ft rear yard covered, half the rear-yard width open), which HCD's 9-1-2026 finding 3 says cannot block an 800 sq ft ADU with 4-ft setbacks (Gov. Code 66321(b)(3)). The ordinance does not say how square footage is measured, while the state floors (850 and 1,000 sq ft) and the 800 sq ft exempt unit are interior livable space. If the city missed HCD's 10-1-2026 response deadline, Gov. Code 66326(d) voids the ordinance and the state standards (1,200 sq ft detached on any lot, attached 50 percent of the home with the 850 and 1,000 sq ft floors) apply instead.

No owner occupancy is required for any ADU, and Gov. Code 66315 forbids one. For a JADU, the deed restriction recorded before the Zoning Clearance (SVMC 9-44.160(E)(2) as restated by Ord. 1373) requires the owner to live in the main home or the JADU only if the JADU shares sanitation facilities with the primary structure, matching Gov. Code 66333(b) as amended by AB 1154, and bars selling the JADU separately. The superseded 2023 text, still printed on Municode and in the July 2023 ADU Guide, imposed owner occupancy on every JADU. An owner who uses the SB 9 urban lot split must live on the property for three years (SVMC 9-24.080), a lot-split rule rather than an ADU rule.

State-exempt ADUs and JADUs (Table 4-4) need no additional parking. A local-track ADU (Class 2 detached or Class 3 attached) needs one space unless it is a studio, sits within a half-mile walk of public transit (defined to include any fixed-route bus stop), lies within the footprint of the existing or proposed home, replaces a garage, carport or covered parking that provided required parking, is in an area where on-street permits are not offered to its occupant, is within one block of a car-share vehicle, is in an architecturally or historically significant district, or is proposed with a new single-family or multifamily home; Ord. 1373 added the last two exemptions after HCD's 2025 findings. Spaces may be uncovered or tandem on paved surfaces, the Director may waive the space where no feasible location exists, and replacement parking for a converted garage cannot be required (Gov. Code 66314(d)(11)). Because studios are exempt, one space per unit stays within the Gov. Code 66314(d)(10) cap of one per unit or per bedroom.

ADUs and JADUs are approved by right: SVMC 9-44.160(A)(3) and (A)(5) as restated by Ord. 1373 call for a ministerial Zoning Clearance with the building permit and approval or denial within 60 days of a complete application, without discretionary review or a hearing. HCD's 9-1-2026 finding 1 says the ordinance omits the 15-business-day completeness determination and the appeal process of Gov. Code 66317 and 66320, which apply directly regardless. ADUs and JADUs are exempt from the Measure N Residential Building Permit Allocation System (SVMC 9-36.020(A)(2)), and there is no coastal zone in Simi Valley.

Ord. 1373 dropped the old rule that every ADU and JADU be rented for 30 days or more: SVMC 9-44.160(A)(7) now defers to state law, which requires terms longer than 30 days for state-exempt units (Gov. Code 66323(e)) and JADUs (Gov. Code 66333(g)), while local-track ADUs carry no local minimum (Gov. Code 66315 makes one optional). Ord. 1370 (adopted 6-8-2026, effective 7-9-2026) made short-term rentals of 30 days or less a permitted use in residential zones with an annual city permit (new SVMC Chapter 5-46), and the Director must deny a permit for any ADU or JADU that state law limits to terms longer than 30 days, so only local-track Class 2 and Class 3 ADUs qualify; the Council did not adopt the Planning Commission and Neighborhood Council suggestion to bar those ADUs too. Each person may hold one STR permit citywide, so an owner can short-term rent the house or the ADU but not both, and a permit needs a transient occupancy registration certificate (10 percent TOT), $500,000 of liability insurance and a Building Official inspection; staff recommended that operators be required to hold permits by 1-1-2027. ADUs cannot be sold separately (no Gov. Code 66342 condominium opt-in), and the city asks owners to complete an ADU Occupancy and Rents Survey for its Housing Element reporting.