Published: 11 Oct 2026 · Last verified: 9 Oct 2026 · Next review: Jan 2027 Cost figures are re-checked against permit records quarterly. Changes are logged in Corrections.
Somewhere in California right now, an architect is redrawing a floor plan from 800 square feet to 749. Not because the client wants a smaller ADU. Because those 51 square feet are worth somewhere between $2,243 and $20,000 — in fees alone.
This is the 750 sq ft cliff, the single most consequential number in California ADU economics, and the concept this site’s entire fee series is built around. Here is how it works, what it costs in real cities, and what changes on January 1, 2027.
The rule
State law — Gov. Code §66311.5, the ADU fee section — says two things:
- ADUs under 750 square feet: no impact fees. Not reduced, not deferred. Zero. Cities, counties, and special districts may not impose them.
- ADUs of 750 square feet or more: fees must be “proportionate” to the primary dwelling — typically (ADU sq ft ÷ house sq ft) × the single-family fee.
Since a 2025 cleanup bill (SB 543), the 750 is measured in interior livable space, and school fees use a different threshold entirely: 500 sq ft (Ed. Code §17620). So a 600 sq ft ADU pays school district fees but no city impact fees — two cliffs, two rulers.
What the cliff costs, city by city
The law sets the threshold. Each city sets the price of crossing it.
| City | At 749 sq ft | At 800 sq ft | The cliff |
|---|---|---|---|
| Torrance | $0 | $2,243.47 flat | A single line in the fee schedule: “ADU 750 SF or greater” |
| Sacramento | $0 | ~$5,728 city impact fees | The “real cliff” — the city’s own free plans are drawn at 747 sq ft for a reason |
| Glendale | $0 | up to $4,700 | The “50 sq ft cliff” — 749 pays nothing, 800 pays the schedule maximum |
| Fullerton | $0 | ~$6,411 pro-rata | DIF on the full 800, scaled to the house |
| Palo Alto | $0 | ~$8,000–$20,000 | The steepest per-foot cliff in the series: $18.65/sq ft parks fee × proportionality |
| Anaheim | $0 | ~$10,411 | The series’ heaviest published DIF load |
| Salinas | $0 | $0 | No cliff at all — the city waives ADU impact fees at every size |
| Oakland | $0 | $0 | Impact fees exempt for ADUs by ordinance |
Two things stand out. First, the range: the same 51 square feet costs $2,243 in Torrance and up to $20,000 in Palo Alto — a 9x spread on an identical design decision. Second, the cities with no cliff at all. Salinas and Oakland have decided ADUs are not the development their impact fees were written for, and their fee schedules say so in plain language.
The design response
Cities know exactly what they are doing at 749, and so do the plan drawers:
- Sacramento’s free ADU plans are drawn at 747 sq ft — three feet under the line, the most literal cliff-avoidance in California.
- Salinas’s pre-approved plans come in 749 and 746 sq ft versions.
- Fontana’s free 738 sq ft plan sits a comfortable 12 feet under.
- Riverside’s Dwell Riverside set includes a 746 sq ft option next to its 800.
When the city’s own architects draw at 747, the cliff is not a subtlety. It is the design brief.
The school-fee shadow cliff
Do not confuse the two thresholds. At 500 sq ft, a second, quieter cliff switches on: school district developer fees, levied by districts under Ed. Code §17620 at $2.24–$5.38 per square foot depending on the district. A 499 sq ft ADU pays no school fee and no impact fee. A 501 sq ft ADU pays school fees (about $2,700–$4,300 on 800 sq ft) but still no impact fees. A 751 sq ft ADU pays both. Garden Grove is the rare city where both cliffs are visible in one schedule — 500 for schools, 750 for DIF.
What SB 1117 changes
Signed September 29, 2026, effective January 1, 2027: for a homeowner’s first two ADUs, impact fees may be imposed only on the square footage above 750 — marginal, not total. An 800 sq ft ADU would owe fees on 50 sq ft, not 800.
The effect scales with the cliff’s height. In Torrance, the flat $2,243.47 has no published per-foot rate, so the city must invent new math. In Palo Alto, roughly $8,000–$20,000 collapses toward roughly $500–$1,250 — the most dramatic single-law savings in the series. In Salinas and Oakland, nothing changes, because there was never a cliff to remove. School fees are untouched: they were never impact fees under the statute.
Permits pulled in 2026 use the old math. If your plans show 800 sq ft and your permit issues in December, you pay the cliff. If it issues in January, you may not. That timing question — worth up to $20,000 in Palo Alto — is the most expensive scheduling decision in ADU construction right now.
The honest bottom line
The 750 sq ft cliff is the closest thing California ADU law has to a cheat code, and it is entirely legal: build at 749 and the impact-fee line of your budget is $0 in every city in the state. Whether those 51 square feet are worth $2,243 or $20,000 depends on your address. Measure twice — in interior livable space — and model both sizes before you commit to a plan set.
Disclaimer
Fee law summary, not legal advice. Thresholds and rates change; SB 1117’s implementation will vary by jurisdiction through 2027. Always verify current fees with your city and school district before budgeting.