Quick Answer: ADUs in Simi Valley cost $60,000–$280,000 in 2026 depending on type. Garage conversions run $60K–$120K. Attached ADUs cost $110K–$200K. Detached ADUs (new construction) run $140K–$280K. JADUs (junior ADUs within the home) cost $35K–$75K. A 1-bedroom detached unit generates $1,600–$2,400/month in Simi Valley’s rental market. Safeway Construction has built ADUs across Ventura County for 20+ years — CA Lic #1066117.
How Much Does an ADU Cost in Simi Valley?
Building an ADU in Simi Valley costs $60,000 to $280,000 in 2026 — depending on the type, size, and what your property already has to work with. A garage conversion on a flat lot in East Simi Valley costs a very different number than a detached 800-square-foot cottage in Wood Ranch. That range is wide, but the variables that drive it are straightforward.
Simi Valley is one of the stronger ADU markets in Ventura County. Median home values around $780,000, solid rental demand, and a city permitting process that has improved significantly since California's 2020–2022 ADU reform laws. If you've been sitting on the idea of an ADU, 2026 is a realistic year to act.
Want a quick ballpark before reading further? Try our free AI estimator at SafewayQuickQuote.com — answer 5 questions, get a real price range in about 2 minutes. No contractor visit required.
ADU Cost by Type in Simi Valley (2026)
| ADU Type | Typical Cost Range | Best For |
|---|---|---|
| Detached ADU (new construction) | $140,000 – $280,000 | Maximum rental income, most privacy |
| Attached ADU (addition to home) | $110,000 – $200,000 | Smaller lots, shared utility connections |
| Garage conversion ADU | $60,000 – $120,000 | Fastest path, lowest entry cost |
| Junior ADU (JADU) | $35,000 – $75,000 | Within main house, under 500 sq ft |
Detached ADU: New Backyard Construction
$140,000 – $280,000
A standalone structure in the backyard is the most popular ADU type among Simi Valley homeowners. It commands the highest rental rates, gives tenants full privacy, and adds the most resale value.
The low end ($140,000–$165,000) covers a 400–500 sq ft unit on a slab foundation: 1 bedroom, 1 bathroom, full kitchen, basic finishes, and all utility connections. The high end ($220,000–$280,000) reflects a 700–850 sq ft unit with premium finishes, or a project on a sloped lot in Wood Ranch or Big Sky where grading and a stepped foundation add $15,000–$35,000.
Per square foot: $280–$380/sq ft standard. Premium finishes or sloped sites push toward $400–$450/sq ft.
Garage Conversion ADU
$60,000 – $120,000
Lowest-cost ADU path in Simi Valley
Most Simi Valley single-family homes have attached 2-car garages in the 400–500 sq ft range. Converting that existing shell is the fastest and most cost-effective ADU path available. The foundation is there. The structure is there. You're converting, not building from scratch.
The $60,000–$80,000 budget covers framing, insulation, drywall, a mini-split HVAC system, new electrical, plumbing for kitchen and bathroom, egress windows, and basic finishes. Above $80,000, costs increase for second bathrooms, premium kitchens, exterior appearance upgrades, or replacing a settled original slab.
One planning note: Simi Valley requires a compliant parking replacement plan when you convert a garage. We handle this analysis during the permit phase.
Attached ADU
$110,000 – $200,000
An attached ADU shares one or more walls with the main house. Think of it as a room addition with a full kitchen, bathroom, and private entrance. It costs more per square foot than a garage conversion but less than a fully detached structure because it shares the existing foundation and often part of the roofline.
Attached ADUs work well on lots where the backyard is too small for a detached structure, or on corner lots where a side-yard addition is possible.
Typical cost for a 500 sq ft attached ADU: $18,000–$38,000 for foundation and framing, $18,000–$32,000 for plumbing and electrical, $5,000–$10,000 for HVAC, $18,000–$35,000 for finishes, and $8,000–$18,000 for permits and school fees.
Junior ADU (JADU)
$35,000 – $75,000
A JADU is a unit of 500 square feet or less created within the existing walls of the main home. Common candidates: an oversized master bedroom with an en-suite, a large bonus room, or a finished lower level on a hillside home. The owner must occupy the main home or the JADU. JADUs are the lowest-cost ADU option — much of the structure already exists. You're adding a separate entrance, a basic kitchen area, and reconfiguring interior space.
What Drives ADU Cost in Simi Valley
Site Conditions
Flat lots in East Simi Valley and central Simi Valley are the most straightforward to build on. Wood Ranch and Big Sky are hillside communities — lots slope, sometimes significantly. Grading, retaining walls, and stepped foundations add $15,000–$45,000 to detached ADU projects in those neighborhoods.
Utility Connections
Running new utility lines from the main home to a backyard ADU is a cost many homeowners underestimate. A 100-foot trench for gas, water, and electrical can add $8,000–$18,000 to your total. The longer the run, the higher the cost.
Finish Level
Basic finishes vs. mid-grade finishes add $15,000–$30,000 to the same footprint. We calibrate finishes to the rental market — there's a point where premium finishes stop increasing your rent but keep increasing your cost.
City Permit Fees and School Fees
The City of Simi Valley charges plan check and permit fees based on project valuation. For most ADUs, total city fees run $4,000–$10,000. The Simi Valley Unified School District charges a school developer fee of $4.14 per square foot for new residential construction, including ADUs. On a 600 sq ft ADU, that's approximately $2,484 — paid to SVUSD before the city issues a building permit.
Simi Valley ADU Permit Process
California state law (AB 2221, SB 13) has made ADU permitting much more predictable. The City of Simi Valley processes most ADU applications ministerially — no public hearings, no neighbor approval required. Here's the process:
- 1
Pre-application check
Confirm ADU eligibility: setbacks, lot coverage, utility capacity. We handle this before you spend anything.
- 2
Design and plans
Architectural drawings, structural calculations if needed, Title 24 energy compliance report. Typically 3–5 weeks.
- 3
Plan check submittal
City of Simi Valley Building and Safety Division (2929 Tapo Canyon Road). Standard plan check: 3–6 weeks. Expedited: 1–2 weeks.
- 4
School developer fee payment
Paid directly to SVUSD before permit issuance. $4.14/sq ft for new residential construction.
- 5
Construction and inspections
Inspections at foundation, framing, rough MEP, and final. Required sign-offs at each stage.
- 6
Certificate of occupancy
Required before the unit can be occupied or rented. We don't hand over keys without a final CO in hand.
Total time from design start to move-in: 10–18 weeks for a garage conversion, 14–22 weeks for a detached ADU.
ADU Rental Income in Simi Valley 2026
Simi Valley sits between Los Angeles County and the rest of Ventura County — which keeps rental demand steady. Here are current rental rate ranges for ADUs in the local market:
| ADU Size | Monthly Rent | Annual Income |
|---|---|---|
| Studio / efficiency (under 400 sq ft) | $1,400 – $1,800 | $16,800 – $21,600 |
| 1-bedroom (450–600 sq ft) | $1,600 – $2,100 | $19,200 – $25,200 |
| 1-bedroom detached / premium | $1,900 – $2,400 | $22,800 – $28,800 |
| 2-bedroom (650–850 sq ft) | $2,200 – $2,800 | $26,400 – $33,600 |
ROI Example
A $180,000 detached ADU generating $2,000/month produces $24,000/year — a gross yield of 13.3% on the build cost. A permitted ADU also typically adds $150,000–$220,000 in appraised property value. That's a build cost that pays for itself and then appreciates.
ADU vs. Room Addition: Which Makes More Financial Sense?
| Factor | ADU | Room Addition |
|---|---|---|
| Generates rental income | Yes — $1,600–$2,800/mo | No (unless in-law suite) |
| Adds sq footage to main home | No (separate structure) | Yes |
| Permitting complexity | Moderate (state laws simplified) | Standard building permit |
| Best scenario | Long-term hold, rental income | Family use, resale-focused |
| Cost range | $60K – $280K | $60K – $200K+ |
| Timeline | 10 – 22 weeks | 12 – 22 weeks |
What Would Your ADU Cost?
Get a real price range for your Simi Valley property in about 2 minutes. Our free AI estimator accounts for ADU type, size, and local permit costs — no contractor visit required.
Get Free Estimate at SafewayQuickQuote.com5 Ways to Reduce Your ADU Cost in Simi Valley
- 1
Start with a garage conversion.
The lowest-cost path. Many Simi Valley homeowners use garage conversion rental income to fund a detached ADU later.
- 2
Keep it under 750 sq ft.
California law exempts ADUs under 750 sq ft from certain impact fees. This threshold matters — confirm with us before finalizing your footprint.
- 3
Use standard dimensions.
Odd dimensions increase framing labor and material waste. Even-number dimensions (12x24, 16x24) keep costs down.
- 4
Match finishes to the rental market, not your personal taste.
Mid-grade finishes rent at the same rate as premium finishes in most Simi Valley markets. There's no income upside to upgrading to marble countertops in a $2,000/month rental.
- 5
Permit correctly the first time.
Unpermitted ADUs can't be legally rented, add no appraised value, and create problems at resale. The permit fee is not where to save money.
Why Simi Valley Homeowners Choose Safeway Construction for ADUs
ADU demand in Simi Valley has grown significantly since 2022. That growth also brought in contractors who treat ADUs as volume work — assembly-line builds with minimal customization and no single point of contact.
We build ADUs the same way we build full kitchen and bathroom remodels. One project manager is assigned from permit to final inspection. We've been building across Ventura County — Simi Valley, Thousand Oaks, Moorpark, Camarillo, Oxnard — for over 20 years. Our 5.0-star Google rating reflects what that consistency produces. Licensed in California (#1066117), fully insured.
We manage the permit process end-to-end: pre-application review, plan check coordination with the City of Simi Valley Building and Safety Division at 2929 Tapo Canyon Road, school fee payment with SVUSD, and all inspections. You don't need to learn how to build an ADU. That's our job.
Frequently Asked Questions: ADU Cost in Simi Valley
How much does a detached ADU cost in Simi Valley in 2026?
A detached ADU in Simi Valley costs $140,000–$280,000 in 2026, depending on size and finishes. A 500 sq ft unit with standard finishes on a flat lot runs $140,000–$180,000. An 800 sq ft unit with premium finishes or on a sloped lot in Wood Ranch or Big Sky reaches $220,000–$280,000.
Is a garage conversion the cheapest ADU option?
Yes. A garage conversion costs $60,000–$120,000 in Simi Valley — the lowest entry cost of any ADU type. The shell and foundation already exist, which eliminates a significant portion of new construction costs. Parking replacement and fire separation requirements are addressed during permitting.
How long does it take to build an ADU in Simi Valley?
Expect 10–18 weeks for a garage conversion and 14–22 weeks for a detached ADU from design start to certificate of occupancy. The permitting phase (design plus city plan check) takes 6–11 weeks before construction begins.
Does Simi Valley charge school fees for ADUs?
Yes. The Simi Valley Unified School District charges a school developer fee of $4.14 per square foot for new residential construction, including ADUs. On a 600 sq ft ADU, this fee is approximately $2,484. It is paid to SVUSD before the city issues a building permit.
How much rent can an ADU generate in Simi Valley?
A 1-bedroom ADU in Simi Valley rents for $1,600–$2,400/month in 2026, depending on size, finishes, and whether it is detached. A 2-bedroom unit rents for $2,200–$2,800/month, generating $26,400–$33,600/year in gross rental income.
Does an ADU increase my property value in Simi Valley?
Yes. A permitted, rentable ADU in Simi Valley typically adds $150,000–$220,000 in appraised property value. Unpermitted ADUs add no appraised value, cannot be legally rented, and create disclosure and financing complications at resale.
What is the difference between an ADU and a JADU?
An ADU is a fully independent dwelling unit — detached, attached, or a garage conversion — with its own entrance, kitchen, and bathroom. A JADU (Junior ADU) is 500 sq ft or less, created within the existing walls of the main house, and requires owner-occupancy of either the main home or the JADU. JADUs cost $35,000–$75,000 and are the lowest-cost ADU pathway.
What's Your ADU Worth? Find Out in 2 Minutes.
If you're in Simi Valley, Thousand Oaks, Moorpark, or anywhere in Ventura County, the fastest way to get a real number is our free AI estimator at SafewayQuickQuote.com. Answer 5 questions about your property and your ADU goals — get a price range you can actually plan around. No sales pitch, no contractor visit required.
Ready to move beyond the estimate? Call us at (805) 222-6544 or use the site to schedule a free consultation. We'll review your lot, your utility situation, and your city's specific requirements — and give you a fixed-price proposal before any work begins.
Safeway Construction — Simi Valley's ADU builders. 20+ years in Ventura County. CA Lic #1066117.