Garage conversion questions from Simi Valley homeowners
Short answers to common Simi Valley garage conversion questions: size limits, sprinklers, half-garage conversions, rentals and unpermitted units.
These are the questions people ask most often before converting a garage in Simi Valley, answered briefly with the law or document behind each answer. The pages on cost, permits and legalization go deeper.
If your question is not here, ask it on the form or by phone. When the answer depends on your lot, you will hear that instead of a guess.
Three facts that settle most early questions
First, whether the converted garage will have a kitchen and its own entrance, which makes it an ADU. Second, whether your driveway can satisfy the City's parking standards if it is not an ADU. Third, whether anything important, like the water heater or the laundry, has to move. Know those three and most of the other answers follow.
Common misunderstandings
Each of these comes up often, and each is wrong:
- A permit is only needed if you add a kitchen. Any conversion to a room people use needs a building permit.
- Myth: Ventura County issues Simi Valley permits. Inside city limits, the City of Simi Valley Building & Safety does.
- The City can make you replace parking for a garage ADU. State law says it cannot (Gov. Code 66314(d)(11)).
- An old unpermitted garage unit must be torn out. For a pre-2020 ADU, Gov. Code 66311.7 limits when the City can deny a permit.
- You must live on the property to have an ADU. Gov. Code 66315 bars that requirement.
Living in a converted garage
Garage walls and roofs were built to shelter cars, not people, so insulation and heating and cooling go into the plan from the start. The wall a garage shares with the house was built as a separation between a car space and living space, and the drawings show how it changes once both sides are rooms.
Questions homeowners ask
How big can a garage conversion be?
For an ADU built inside the existing garage, local size limits do not apply, and the structure can grow up to 150 square feet only for ingress and egress (Gov. Code 66323(a)(1)(A), HCD ADU Handbook, March 2026).
Will I need fire sprinklers?
Not because of the conversion. An ADU needs sprinklers only when the main house requires them, and building an ADU does not trigger them (HCD ADU Handbook, March 2026).
Can I convert only part of my garage?
Yes. For a partial attached-garage ADU, Ordinance 1349 required the remaining space to stay parking if it measured at least 12 by 20 feet. That rule is superseded pending Ordinance 1373, so confirm it with the City.
What if a previous owner converted the garage without a permit?
Start with a confidential third-party code inspection by a licensed contractor, which state law says you may get before applying (Gov. Code 66311.7(d)). The legalization page explains the rest.
How fast must the City decide on a garage ADU?
For a complete ADU application with a house already on the lot, the City must approve or deny within 60 days (Gov. Code 66317).
Can I rent out the converted garage?
As an ADU, yes, with rentals longer than 30 days for conversion units. A bedroom inside your house is not a separate unit, so renting it is a room rental, not an ADU tenancy.
Sources
Facts on this page last verified: .
- California HCD, Accessory Dwelling Unit Handbook, March 2026: https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/adu-handbook-update.pdf (2026-10-05)
- City of Simi Valley, second reading of Ordinance No. 1349, staff memo of June 5, 2023: https://simivalley.granicus.com/MetaViewer.php?view_id=5&clip_id=2792&meta_id=204582 (2026-10-05)
- California Government Code section 66311.7: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=66311.7. (2026-10-05)
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