What a Simi Valley garage conversion costs, and why ranges vary
Simi Valley garage conversion costs: competitor-published ranges with dates, the City's July 2024 permit fees, and the line items that move a total up or down.
There is no honest single number for a garage conversion, and this page will not give you an Aguila price before anyone has seen your garage. What it can give you is the public numbers other contractors publish, what the City charges, and the line items that move the total.
Every figure below carries its source and date. Competitor numbers are their published ranges, not quotes, and they describe full ADUs with a kitchen, which cost more than a bedroom or office conversion.
Ranges other contractors publish
Two published sources describing a 400 square foot garage ADU start about $20,000 apart, and the higher source's floor sits well above the lower source's ceiling. That spread is normal: finishes, utilities and what turns up in the slab and framing decide where a job lands.
| Source | Scope | Published range | Date on the page |
|---|---|---|---|
| Safeway Remodel | 400 sq ft garage ADU: one bedroom, one bath, laundry, private entrance | $130,000 to $180,000 | Factual update September 16, 2026 |
| Paul's General | 400 sq ft garage ADU, standard bath and basic kitchen | $150,000 and up | September 30, 2024 |
| Paul's General | 400 sq ft garage ADU, full kitchenette | $250,000 and up | September 30, 2024 |
| Paul's General | 400 sq ft garage ADU, custom bath and kitchenette, patio awning | $300,000 and up | September 30, 2024 |
What the City charges
The City of Simi Valley's Summary of Service Charges, effective July 1, 2024, lists a garage conversion of conventional construction at $1,376.24 for the first 500 square feet plus $325.12 for each additional 500 square feet, and a special-design conversion at $1,510.45 plus $392.22. Reinspections are billed at $190.91 per hour and extra plan check at $268.41 per hour. The City revises its schedule, so confirm current figures before you budget.
A garage ADU of 750 square feet or less is exempt from impact fees under state law (HCD ADU Handbook, March 2026). For a pre-2020 unpermitted unit, AB 2533 waives impact fees and connection charges unless utility upgrades are needed to fix a substandard condition.
Line items that move the total
A useful estimate lists each of these separately, so you can see what changes if you drop the kitchen or leave the laundry where it is.
- Use: a kitchen turns a room into an ADU and adds the most cost.
- Bathroom: new drain lines under a slab mean cutting and patching concrete.
- Floor height: bringing the floor up to the house level adds framing or fill.
- Relocations: a water heater or laundry that has to move, or a panel with no spare capacity.
- The street face: matching stucco or siding and a window where the door was.
- Hidden condition: termite damage, a cracked slab or old unpermitted work found when walls open.
Paying for plans and permits
CSLB's consumer alert on home improvement and ADU payments tells homeowners to be careful about paying for plans or permits before work starts, to ask for an accounting of what the plans cost, and to confirm permit costs with the building department. Any progress payment has to match work already performed or materials already delivered.
Questions homeowners ask
Why won't you post your own prices?
Because a price given without seeing the slab, the panel and the drain lines is a guess, and a low guess turns into change orders. You get a written, line-item estimate after the walk-through.
Is a bedroom conversion cheaper than a garage ADU?
Usually, because it skips the kitchen and often the separate utilities. The competitor ranges above are for ADUs with kitchens, so read them as a ceiling for a plain living-space conversion, not a target.
Should City permit fees appear in an estimate?
Yes, as their own line at the City's published rate, so you can check them. CSLB tells homeowners to confirm permit costs with the building department, and that advice holds here.
Do school fees apply to a garage ADU?
Under the HCD ADU Handbook (March 2026), ADUs under 500 square feet of interior livable space are not subject to school impact fees. The line for other local impact fees is 750 square feet, so a 600 square foot garage ADU can owe school fees while skipping the rest. Check with the school district.
Sources
Facts on this page last verified: .
- Safeway Remodel, ADU cost in Simi Valley (competitor-published, factual update September 16, 2026): https://www.safewayremodel.com/blog/adu-cost-simi-valley-2026 (2026-10-05)
- Paul's General, garage conversion ADUs (competitor-published, page dated September 30, 2024): https://www.paulsgeneral.com/garage-conversion-adus/ (2026-10-05)
- City of Simi Valley, Summary of Service Charges effective July 1, 2024: https://simivalleylibrary.org/wp-content/uploads/2025/02/CityofSimiValley_FeeSchedule2025.pdf (2026-10-05)
- CSLB consumer alert, Don't Pay Too Much Money Upfront on Home Improvement Projects: https://www.cslb.ca.gov/Resources/PressReleases/2024/ADU-payments.FINAL.pdf (2026-10-05)
- 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)
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