Published: 5 Oct 2026 · Last verified: 5 Oct 2026 · Next review: Jan 2027 Cost figures are re-checked against permit records quarterly. Changes are logged in Corrections.
Every other post in this series has a 750 square foot cliff. This one barely does — and that absence is the whole story.
San Francisco is a consolidated city-county, so there is no neighboring jurisdiction to compare against. No Encinitas with a $0 fee schedule twenty-five miles from a $16,500 one. One city, one fee schedule, one answer. And the answer is strange: the permit and planning bill on an 800 sq ft detached ADU runs about $19,500 — higher than the City of San Diego’s $16,500 — yet the impact-fee cliff that makes San Diego homeowners count every square foot past 750 barely exists here at all.
So this post does two things. First, the standard six-phase breakdown for an 800 sq ft detached ADU in San Francisco — $325,000, or $406 per square foot. Then the part nobody publishes: an autopsy of the soft-cost line, fee by fee, from the city’s own schedules.
The short answer
| 800 sq ft detached ADU · San Francisco · 2026 | Amount |
|---|---|
| Total build cost | $325,000 |
| Cost per square foot | $406 |
| Largest single line | Systems + interior, $147,000 |
| DBI + Planning fees (worked example) | ≈ $19,500 |
| SFPUC capacity charges | $0 |
| School district fees | $3,032 |
The full line-item breakdown
Six phases. The same six used on every build in this series.
| Phase | Cost | Share |
|---|---|---|
| Soft costs (design, permits, plan check) | $37,000 | 11% |
| Site work + foundation | $38,000 | 12% |
| Framing + structure | $48,000 | 15% |
| Building envelope | $42,000 | 13% |
| Systems + interior | $147,000 | 45% |
| Landscaping & hardscape | $13,000 | 4% |
| Total | $325,000 | $406 / sq ft |
Shares rounded.
One honest caveat before the tables: San Francisco’s agencies do not publish phase-level construction costs, and we found no public San Francisco permit-valuation dataset to anchor one. So phases two through six are carried from the Los Angeles County baseline, unchanged — the Bay Area labor premium is real, but we will not print a number we cannot anchor. What is rebuilt from San Francisco sources, line by line, is the soft-cost phase. That is where this city’s story lives.
Where San Francisco differs from Los Angeles
| Phase | LA County | San Francisco | Difference |
|---|---|---|---|
| Soft costs | $32,000 | $37,000 | +$5,000 |
| Site work + foundation | $38,000 | $38,000 | — |
| Framing + structure | $48,000 | $48,000 | — |
| Building envelope | $42,000 | $42,000 | — |
| Systems + interior | $147,000 | $147,000 | — |
| Landscaping & hardscape | $13,000 | $13,000 | — |
| Total | $320,000 | $325,000 | +$5,000 |
| Per sq ft | $400 | $406 | +$6 |
The totals are almost identical. Do not mistake that for the cities being interchangeable. The $5,000 gap is the net of large offsetting differences inside the soft-cost line — and the differences that matter most in San Francisco are about fee structure, not fee totals.
The fee autopsy: $19,500, line by line
San Francisco prices ADU permits from two separate schedules. Here is what each one says at an 800 sq ft detached ADU, worked from the published rate tables at an assumed $320,000 valuation. These are worked examples, not quotes — the Building Official sets the final valuation.
DBI — permit issuance + plan check: ≈ $7,515. Table 1A-A of the San Francisco Building Code (Section 110A), as amended by Ordinance 112-26 effective 12 Jul 2026. At a $320,000 valuation: $1,402 + $4.21 × 120 for issuance ($1,907.20) and $4,011 + $13.31 × 120 for plan review ($5,608.20). Plumbing, electrical, and mechanical permits bill from separate tables and are not in this figure.
Planning Department — permit review: ≈ $11,985. The FY25-26 application fee schedule, effective 1 Jan 2026: $3,504 + 3.855% on the $100,000–$499,999 bracket, which at $320,000 works out to $3,504 + 3.855% × $220,000.
Combined: ≈ $19,500 — before trade permits. That is the highest permit-and-planning line in this series so far, above the City of San Diego’s $16,500. And then the bill mostly stops.
“There are no additional fees for ADUs”
That is a direct quote from the San Francisco Planning ADU fact sheet: “There are no additional fees for ADUs. The normal fees for the permit application and issuance apply.” No ADU surcharge exists. The development impact fees that create cliffs elsewhere do not land here:
- Transportation Sustainability Fee: residential TSF applies only to developments of more than 20 new dwelling units (Impact Fee Schedule). One ADU is not twenty units.
- SFPUC capacity charges: $0. SFPUC’s official guidance: “In most cases, ADUs are not assessed additional capacity charges.” On a single-family lot, water and wastewater capacity charges are not applicable, and no meter upsizing is required. State law independently bars treating an ADU as a new dwelling unit when calculating connection fees (Gov. Code § 66311.5).
The 750 square foot cliff that isn’t
In the San Diego post, crossing from 750 to 800 sq ft triggers $5,000–$8,000 in newly applicable impact fees — the marginal 50 sq ft effectively costs $530–$590 per foot. In San Francisco, that math collapses, because there is almost nothing left to trigger:
| Fee that creates the cliff elsewhere | San Francisco |
|---|---|
| Local transportation / development impact fees | TSF: 20+ units only — not applicable |
| Water / sewer capacity charges | $0 on single-family lots (SFPUC) |
| ADU-specific surcharges | None — “no additional fees for ADUs” |
| School district developer fees | $3,032 |
School fees are the one line that still steps at a size threshold — they sit under a separate Education Code framework, and junior ADUs (under 500 sq ft) are now exempt statewide (Gov. Code § 66311.5). SFUSD’s developer fee is $3.79 per square foot of residential construction (San Francisco’s development impact fee register) — 800 × $3.79 = $3,032, now included in the soft-cost total above. Treat the 750 sq ft decision in San Francisco as a design decision, not a fee decision — the opposite of San Diego, where it is the most expensive checkbox on the drawings.
The empty shelf: pre-approved plans
San Francisco has a pre-approved ADU plan program. Under AB 1332, designers may submit detached ADU plans for DBI’s basic review and publication — for a $2,408 flat submission fee paid by the designer.
As of September 2026, the city’s published library contains zero approved plans.
The program exists; the shelf is empty. So unlike Escondido — which publishes four free pre-approved plans outright — or the City of San Diego, which accepts other jurisdictions’ plans with a 30-day review, San Francisco offers no design-cost relief at all. The $14,000 design and engineering line in the table above is yours in full. Check the library before you hire an architect anyway — on the off chance the shelf gets stocked, the savings are five figures — but do not budget around it.
Deferral is not a waiver
One more San Francisco original: the city lets ADU builders defer Planning Code §350 and Building Code §107A.4 fees until the certificate of occupancy or 24 months after first construction-document approval, whichever comes first (Board File 2025-006257PCA). File the deferral application before the first construction documents issue.
Read that carefully: defer, not waive. Nothing gets cheaper; the cash just moves later in the project. Contrast Encinitas, which waives its Development Services fees outright. San Francisco’s version improves cash flow, not cost — which is still worth knowing, because $19,500 of fees paid at permit issuance versus at occupancy is a different loan.
What moves the number most in San Francisco
1. Site conditions. More than anywhere else in this series. Hillside lots, liquefaction zones, and Maher Zone parcels each add their own reports, engineering, and foundation work — and can disqualify pre-approved plans even if the shelf ever gets stocked. Flat-lot Richmond versus hillside Diamond Heights is not the same build.
2. School fees, now confirmed. SFUSD’s developer fee is $3.79/sq ft ($3,032 on 800 sq ft), verified against the city’s impact fee register and included in the total above — see Corrections.
3. Design and engineering, unoffset. With no usable plan library, the full $14,000 design line is structural to the budget here in a way it is not in Escondido or San Diego.
4. ADU type. This post models new detached construction (Table 1A-A new-construction rates). A garage conversion bills under the alterations rate schedule with the shell already standing; a JADU is exempt from impact fees statewide and, since 2026, from school fees too. Type selection moves the number more than finish grade does.
5. Finish grade. $15,000 to $30,000 across a full unit between builder-grade and mid-grade — same as everywhere.
What this number does not include
| Not included in $325,000 | Typical impact |
|---|---|
| Construction loan interest | Carried 9 to 14 months |
| Property tax reassessment | Only the new construction is added (Prop 13) |
| Vacancy before first tenant | 1 to 3 months is common |
| Property management | 8% to 10% of rent |
| Contingency | 10% to 15% — budget it, don’t hope |
A 12% contingency on this build is $38,640.
→ Full year-one ownership cost: ADU all-in cost in California
→ The Bay Area companion, where the swing is impact fees rather than permits: San Jose ADU cost
Put your own quote in these six rows
We made a blank version of the six-phase ledger. Drop your contractor’s numbers into it and see which line doesn’t match ours.
Download the worksheet — CSV (import to Google Sheets), no email required
Compare any two builds side by side →
Want the regional benchmark ranges for each phase, updated quarterly?
Methodology and sources
Every figure on this page is a modeled median, not a quote. Here is exactly how it was built, so you can check it or reproduce it yourself.
| Input | Source |
|---|---|
| DBI permit issuance + plan check rates (Table 1A-A, new construction) | SF Building Code §110A Table 1A-A · Ordinance 112-26 (eff. 12 Jul 2026) |
| Planning Department application fee schedule FY25-26 | Fee schedule (eff. 1 Jan 2026) · Fee schedule resource page |
| “No additional fees for ADUs” | SF Planning ADU Program fact sheet |
| SFPUC capacity charges on ADUs ($0, single-family) | SFPUC capacity charges · ADU capacity-charge guidelines |
| Transportation Sustainability Fee threshold (20+ units) | Citywide Development Impact Fee Register |
| Pre-approved ADU plan program ($2,408, zero plans published) | SF.gov pre-approval program page |
| Fee deferral program (Planning Code §350) | Board File 2025-006257PCA |
| State ADU law: 750 sq ft impact-fee exemption | Gov. Code § 66311.5 (SB 543, eff. 1 Jan 2026) · ABAG state-law summary |
| JADU school-fee exemption (2026) | Gov. Code § 66311.5 |
| Daly City ADU planning fee ($780 flat, neighbor contrast) | Daly City Master Fee Schedule FY2025 |
| Construction phases 2–6 (carried from LA baseline) | 800 sq ft ADU cost — Los Angeles County · Methodology |
| Phase-level cost shares for residential construction | NAHB Cost of Construction Survey |
| Per-square-foot construction price benchmarks | NAHB Survey of Construction |
On the fee examples. DBI and Planning figures are worked examples from the published rate tables at an assumed $320,000 valuation, checked 5 Oct 2026 — the current schedules, not the superseded 2025 PDFs still floating around search results. The Building Official sets the final valuation, and trade permits (plumbing, electrical, mechanical) bill separately. Pull the current schedule for your own project before you budget — the examples above are a shape, not a quote.
On the construction phases. San Francisco’s agencies do not publish phase-level construction costs, and we located no public San Francisco permit-valuation dataset for ADUs. Phases two through six are therefore carried unchanged from the Los Angeles County baseline rather than adjusted by an unanchored regional factor. If you hold San Francisco permit valuations or contractor data, we want them — see Corrections.
Check this number against your own address
- Search SF DBI permit tracking for recent ADU permits near your address.
- Note the declared construction valuation on comparable units.
- Compare it to the phase totals on this page.
Declared valuations run below contract price — treat them as a floor, not a total. Full detail on Methodology.
If your local numbers diverge meaningfully from ours, we want to know. See Corrections.
Our position
We don’t build ADUs. We don’t sell plans. We don’t sell your information to contractors. No figure on this site has been paid for or reviewed by anyone whose costs we publish. More on About.
Figures are San Francisco, 2026, stated as medians of contractor ranges. Costs vary by site conditions — hillside, liquefaction, and Maher Zone parcels in particular — and finish level. School district fees ($3,032 at SFUSD’s $3.79/sq ft) are included in the $325,000 total. This is construction cost information — not a quote, and not legal, engineering, or financial advice. Confirm requirements with the San Francisco Department of Building Inspection and a licensed California contractor.
Frequently asked questions
How much does an ADU cost in San Francisco in 2026?
About $325,000 for an 800 sq ft detached, single-story, new-construction unit with mid-grade finishes in San Francisco — roughly $406 per square foot. That is our modeled median: permit and planning fees are rebuilt from the city’s official fee schedules, while construction phases are carried from the Los Angeles County baseline because San Francisco does not publish phase-level construction costs.
Why is there (almost) no 750 sq ft fee cliff in San Francisco?
The cliff is a creature of local impact fees, and San Francisco barely levies any on a single ADU. The Transportation Sustainability Fee applies only to developments of more than 20 new units, SFPUC assesses $0 in water and wastewater capacity charges on ADUs on single-family lots, and state law bars treating an ADU as a new dwelling unit for connection-fee purposes. The one fee that still steps at a size threshold is the school district developer fee: $3.79 per sq ft.
How much are ADU permit fees in San Francisco?
Applying the city’s current fee schedules to an 800 sq ft detached ADU at a $320,000 valuation gives about $7,515 for DBI permit issuance plus plan check (Table 1A-A, as amended by Ordinance 112-26) and about $11,985 for Planning Department permit review (FY25-26 schedule) — roughly $19,500 combined, before separate plumbing, electrical, and mechanical permits. Those are worked examples from the published rate tables, not a quote; the Building Official sets the final valuation.
Does San Francisco have pre-approved ADU plans?
The program exists on paper — designers can submit detached ADU plans for a $2,408 flat fee — but as of September 2026 the city’s published library holds zero approved plans. In practice there is nothing to download, so expect to pay full design and engineering costs. Contrast Escondido, which publishes four free pre-approved plans outright.
Do I pay water or sewer capacity charges for an ADU in San Francisco?
On a single-family lot: no. SFPUC’s official guidance states that water and wastewater capacity charges are not applicable to ADUs on single-family lots, and no meter upsizing is required. (ADUs added to multifamily buildings are assessed — a different scenario from this post.)