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Simi Valley, Ventura County
ADUs & home additions in Simi Valley, CA.
Simi Valley has become one of Ventura County's busiest ADU markets for garage conversions, backyard units and room additions.
Building in Simi Valley
Simi Valley lots are made for ADUs.
Many Simi Valley homes are single-story ranch and tract houses with attached garages and usable backyards, which makes them strong candidates for garage conversions and detached ADUs.
A garage conversion here often follows a familiar pattern: cut the slab for plumbing, pour a leveling slab, insulate to living-space standards and, where the framing is sound, keep the existing roof to gain vaulted ceilings. On backyard units, the distance to the sewer and the capacity of the electrical panel are the first things to check.
The city actively tracks ADU production toward its housing goals and asks new ADU owners to complete a short occupancy and rent survey after final inspection. HCD has also identified parts of the local ordinance that do not comply with state law, so it is worth confirming which standards apply before design.
What to know in Simi Valley
- ADU planning is handled by the Planning Division of the Department of Environmental Services.
- The city's Housing Element aims for at least 256 new ADUs from 2021 to 2029, and owners are asked to complete an ADU Occupancy and Rents Survey within 30 days of final inspection.
- HCD's October 2025 review of Simi Valley's ADU ordinance identified issues, including a six-foot separation requirement between a detached ADU and other structures. Where local rules conflict with state law, state law controls.
Project types in Simi Valley
ADUs and additions in Simi Valley.
ADUs
Accessory dwelling units of every type, from feasibility and permits through final inspection.
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Garage-to-ADU Conversions
Reuse an existing garage for the fastest, most economical path to a complete ADU.
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Detached ADUs
Freestanding backyard homes with full foundations, framing, utilities and finishes.
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Attached ADUs
Units that share a wall with the main house, including attached-garage conversions.
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Junior ADUs (JADUs)
Up to 500 square feet created within your existing home, with an efficiency kitchen.
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Home Additions
Room additions, kitchen expansions and roof decks built to blend with your home.
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Second-Story Additions
Build up instead of out, with structural evaluation, engineering and framing done right.
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Primary Suite Additions
Master bedroom and bathroom additions with closets, showers and soaking tubs.
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Simi Valley ADU & addition questions
Who handles ADU permits in Simi Valley?
The Planning Division within the Department of Environmental Services reviews ADU planning, with building permits issued after plan check.
Does a detached ADU in Simi Valley need to be six feet from the house?
The local ordinance has included a six-foot separation, but HCD found it inconsistent with state law in October 2025. The contractor confirms the current standard for your lot.
Can I convert my garage in Simi Valley without replacing the parking?
Yes. State law does not allow cities to require replacement parking when a garage is converted to an ADU.
Nearby areas
Also serving areas near Simi Valley.
Free consultation
Planning an ADU or addition in Simi Valley?
Share a few details about your property and the space you want to add. We will pass your request to a licensed local general contractor who specializes in ADUs and additions, and they will follow up directly.
- Free consultation and site visit
- A realistic budget conversation before you pay for plans
- A licensed general contractor from permit to final