Step 1 — Confirm the lot is multifamily-zoned.
"Multifamily" means R-2, R-3, R-4, RM, or equivalent — not R-1 single-family. Check your zoning at the City's GIS map (free, online for Modesto, San Jose, and Stanislaus County).
A lot with a duplex on it isn't automatically multifamily-zoned; some duplexes sit on R-1 lots due to historical use and only qualify for 1–2 ADUs under different rules. Verify the zoning designation in writing before spending a dollar on design.
Step 2 — Run the unit-count math.
SB 1211 allows up to 8 detached ADUs on a multifamily lot, in addition to the existing primary units.
Math: existing units + 8 ADUs = total. A duplex with 2 units could go to 10 total. But the physical lot has to actually fit them — setbacks (4 ft side and rear), height (16 ft max for single-story), and lot coverage rules still apply.
A 6,000 sq ft lot will not realistically support 8 ADUs no matter what the statute says. A 12,000+ sq ft lot in most CA cities can.
Step 3 — Pre-application meeting with the City.
Modesto and San Jose both offer free pre-application meetings. Bring:
- Your lot survey
- A concept site layout showing proposed ADU footprints, setbacks, and parking
- Your unit-count summary
The planner will flag issues before you spend $5K on plans. This step saves more money than any other in the process — it's free and takes 45 minutes.
Step 4 — Hire a designer who's done SB 1211 in your city specifically.
The state law is uniform. Local interpretation is not. Some cities are still requiring CC&R reviews on properties with old recorded restrictions. Some are challenging the 16-ft height rule. A designer who's already gotten one approved in your city knows the local quirks — and will save you 3 months of back-and-forth.
Step 5 — Pull the permit, build, finalize utilities.
Each ADU needs separate metering (water, gas, electric) unless your jurisdiction allows shared metering — which most don't for new construction. Budget $8–15K per ADU for utility hookups alone, on top of construction.
PG&E and the local water district have 60–120 day lead times for new service. Get applications in the day your permit is issued, not after framing.
Step 6 — Know the financing structure.
Most investors are using one of three financing structures:
- HELOC on the primary building. Cheapest interest, simplest. Caps at ~$200K for most lots.
- Construction-to-perm loan. Funds release at milestone inspections. Best for builds over $400K.
- Cash + cash-out refi after C of O. Best when interest rates are unfavorable for new debt.
The big banks were slow to adapt to SB 1211 — credit unions and local lenders move faster on these. Ask specifically: "Do you have an SB 1211 multifamily ADU product?"
Typical timeline.
4–6 months from permit application to final inspection per ADU, faster if built in series with the same crew. A property going from 2 units to 6 units (4 new ADUs) is realistically a 12–14 month project from concept to last C of O.
The single biggest mistake: Designing all 8 ADUs at once and trying to permit them together. Cities choke on the volume and the review extends 6–12 months. Permit 2–3 at a time, in phases, and the timeline stays manageable.
What success looks like.
A multifamily lot that produced 2 rental units now produces 6–10. Cash flow doubles or triples. Property value increases substantially. The build cost amortizes within 6–10 years against the increased rental income.
Done badly: the permits stall, utility hookups blow the budget, and the ADUs sit half-built waiting for engineering revisions.
Skip the DIY?
FXR has built ADUs across Modesto, San Jose, Turlock, and Stockton — from concept design to final inspection. CSLB #1005035. End-to-end project management.
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