How Simi Valley Handles Accessory Structures: A Practical Guide

Simi Valley maintains 74 local ordinances across all categories, and 5 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Simi Valley falls on the strict-to-permissive spectrum compared to other cities.

Tiny Homes

Tiny homes on foundations in Simi Valley are regulated as ADUs or standard dwellings and must meet California Building Code requirements. Tiny homes on wheels are classified as RVs and may not be used as permanent residences on residential lots.

Key details: On Foundation: Regulated as ADU, permits required. On Wheels: Classified as RV, no habitation. HCD Certification: Required for factory-built units. Minimum Size: Must meet CBC habitable standards.

Living in a tiny home on wheels on a residential lot is a zoning violation. Unpermitted tiny homes on foundations are building code violations subject to stop-work orders and removal. Using a THOW as a permanent dwelling results in Code Enforcement action with fines starting at $100 per day.

Carport Rules

Simi Valley regulates carports as accessory structures under SVMC 9-30.080 (Table 3-2 setbacks; accessory structures may not cover more than 40 percent of any yard) and as covered parking under Chapter 9-34 (parking stall must be a clear 9 by 18 feet with no encroachment from posts). A building permit is required, and ADU-replacement carports must follow SVMC 9-44.160.

Key details: Accessory Structure Code: SVMC 9-30.080 (Table 3-2). Yard Coverage Cap: 40 percent of any yard. Parking Stall Clear Dimension: 9 ft by 18 ft (SVMC 9-34.080). Post Encroachment: Not allowed into stall. ADU Replacement Parking: SVMC 9-44.160 (covered, uncovered, or tandem).

Building a carport without a permit, exceeding the 40 percent yard-coverage cap, intruding into required setbacks under Table 3-2, or installing posts that reduce a parking stall below the 9 by 18 foot clear dimension can trigger code-enforcement action, stop-work orders, and required removal or modification before the structure may be used. Use of a carport for STR-style hosting is independently prohibited under SVMC 9-22.030.A.1.

Garage Conversions

Simi Valley ministerially allows an attached or detached garage to be converted to an ADU under SVMC 9-44.160(E)(1) — no additional setbacks are required when keeping the existing footprint, and lost garage parking is generally waived under state law.

Key details: Code section: SVMC 9-44.160(E)(1)–(2), A(11), A(17). Setback relief: Same footprint = no new setbacks required. Ingress/egress bonus: Up to 150 sq ft expansion allowed. Replacement parking: Not required when a garage is converted to an ADU. Partial garage conversion: Remaining space must keep parking if ≥ 12 × 20 ft.

Occupying a converted garage as an ADU without a Zoning Clearance, building permit, and California Building Code compliance can trigger code enforcement and require removal of habitable improvements; converting a garage that was not legally permitted in the first place forfeits the relaxed setback and parking allowances.

If you are coming from a city with tighter rules, you will find Simi Valley gives residents more flexibility on garage conversions.

ADU Rules

Simi Valley permits one ADU plus one JADU per single-family lot ministerially under SVMC 9-44.160, conforming the city to state law (Gov't Code 65852.2 and 65852.22) with 4-ft side/rear setbacks, 18-ft height, and up to 1,200 sq ft detached.

Key details: Code section: SVMC 9-44.160 (Ord. 1316, Nov. 2, 2020; amended 2023). Review: Ministerial Zoning Clearance, 60-day deadline. Setbacks: Front 20 ft; side 4 ft; rear 4 ft. Height: 18 ft, single story. Detached ADU max size: 1,000 sq ft (parcels ≤8,000 sq ft); 1,200 sq ft (parcels >8,000 sq ft).

Building or occupying an ADU without a Zoning Clearance and building permit can trigger code enforcement, stop-work orders, and a requirement to remove or legalize the structure; a JADU rented out without the recorded owner-occupancy deed restriction must be vacated within 90 days of a new owner taking title.

The rules around adu rules in Simi Valley lean permissive, but that does not mean anything goes.

Shed Rules

Detached freestanding sheds and similar nonresidential accessory structures must sit at least 20 ft from the front, 3 ft from side and rear lot lines per SVMC 9-30.080 Table 3-2, may cover no more than 40% of any yard, and require a building permit if the floor area exceeds 120 square feet.

Key details: Code section: SVMC 9-30.080 Table 3-2 (Ord. 1316). Shed setbacks: Front 20 ft; side 3 ft; rear 3 ft. Maximum height: 18 ft (Figure 3-7). Yard coverage: ≤ 40% of any yard, cumulative. Permit threshold: Building permit required if > 120 sq ft.

Constructing a shed over 120 sq ft without a building permit, or placing any shed inside the required 3-ft setback, can trigger code enforcement, fines, and an order to relocate or remove the structure under SVMC Title 1 enforcement provisions.

The Bottom Line

Compared to many U.S. cities, Simi Valley gives residents more room on accessory structures. 2 of the 5 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

This guide is based on Simi Valley's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.