California has passed more ADU-related legislation in the last decade than any other state in the country. The laws are overwhelmingly in your favor as a homeowner — they remove local barriers, mandate faster permitting, limit what cities can deny, and create financial opportunities (including the potential to sell your ADU as a separate condo unit) that didn’t exist five years ago.
But the sheer volume of legislation — more than a dozen bills since 2016, with four more signed in 2025 taking effect January 1, 2026 — makes it difficult for homeowners to understand what actually applies to their project. Which setback rules apply? Can the city deny your application? Do you need to live on the property? Can you rent it short-term? What’s the maximum size? What happened with the separate-sale provision?
This page consolidates the California ADU laws that matter for homeowners on the San Francisco Peninsula. Not a legal analysis of every bill. Not a history of ADU legislation. Just the rules that affect what you can build, where, how big, how fast, and what you can do with it when it’s finished — organized around the questions we hear from homeowners in Pacifica, Daly City, San Francisco, South San Francisco, and the rest of the Peninsula every week.
ACI is a design-build general contractor based in Pacifica. We build ADUs across the Peninsula and navigate the permitting process in every city in our service area. This page reflects state law as of January 2026, including the four bills signed by Governor Newsom in October 2025. Local ordinances vary by city — we know the local rules in every Peninsula jurisdiction we serve.
The Core Right — Ministerial Approval
If your ADU application meets the zoning standards — setbacks, height, size, and the other objective criteria in state law and your city’s ADU ordinance — the city must approve it. The approval is ministerial, meaning it happens by right. No discretionary review. No public hearing. No neighbor approval. No Planning Commission vote. No design review board.
This is fundamentally different from how most construction projects are permitted. A room addition in San Francisco can trigger 30-day neighborhood notification and Discretionary Review before the Planning Commission. An ADU cannot. The city reviews your application against the checklist of objective standards, and if you meet them, the permit is issued.
The 60-Day Clock
State law requires the city to approve or deny a complete ADU application within 60 days of receiving it. If the city fails to act within 60 days, the application is deemed approved. The 2025 legislation SB 543 added procedural safeguards: the city must determine whether your application is complete within 15 business days of submission, must notify you in writing if anything is missing, and must provide an appeal process if the application is denied.
"Complete" Is the Operative Word
The 60-day clock starts when the city determines your application is complete — meaning all required documents (plans, structural engineering, Title 24 calculations, and any other items the city specifies) are included. An incomplete application doesn’t start the clock. This is why submitting a thorough, code-compliant plan set matters — it starts the clock on day one and minimizes correction cycles.
What the City Cannot Do
Under state law, the city cannot impose subjective design standards on ADUs (no design review panels judging your aesthetic choices), cannot require public hearings, cannot condition ADU approval on neighborhood consent, and cannot adopt local ordinances that unreasonably restrict the ability to create ADUs. The 2025 legislation SB 543 explicitly added that last point — local ordinances “shall not unreasonably restrict” ADU and JADU creation. If a local ordinance doesn’t comply with state law and the city fails to correct it after review by the Department of Housing and Community Development (HCD), the ordinance is null and void.
Setbacks, Height, and Size — What You Can Build
Setbacks
4-foot side and rear setbacks, regardless of what your local zoning says. This is the provision that makes ADU construction possible on tight Peninsula lots where the underlying zoning might require 10- or 20-foot rear setbacks.
Local setback requirements apply. These vary by city and zoning district — in some Peninsula cities, rear setbacks for the underlying zone may be 15 to 20 feet.
Local setback requirements generally apply for the primary structure, but an attached ADU of 800 SF or less qualifies for the 4-foot minimum setbacks on the ADU portion.
No setback issue — the garage already exists in its current location. Even if the garage is within the 4-foot setback, the conversion is allowed because you’re not creating a new structure.
State law doesn’t override front setbacks. Your ADU must comply with the local front setback requirement (typically 15 to 25 feet from the front property line, depending on the city and zone). This is why most detached ADUs are placed in the rear yard.
Height
State law allows detached ADUs up to 16 feet in height. For ADUs within half a mile of a major transit stop (which includes BART stations and Caltrain stations — covering most of the Peninsula’s urbanized corridor), the height limit increases to 18 feet for single-story or 25 feet for multi-story ADUs.
Local jurisdictions can set their own height limits within these state parameters, and some Peninsula cities have adopted lower limits in certain zones. We check the specific height allowance for your lot during site assessment.
Two-story ADUs — possible under the 25-foot allowance near transit — are increasingly practical on the Peninsula, where lot area may be limited but a second level doubles the livable space without expanding the footprint.
Size
ADU maximum: State law allows ADUs of at least 850 square feet for a studio or one-bedroom, and at least 1,000 square feet for two or more bedrooms. Local ordinances can allow larger. Some Peninsula cities permit ADUs up to 1,200 square feet. The maximum for your lot depends on your city’s ordinance, the underlying zoning, and any applicable lot coverage limits (though state law exempts ADUs of 800 square feet or less from local lot coverage restrictions on lots of 4,000+ square feet).
JADU maximum: 500 square feet of interior livable space. The 2025 legislation SB 543 clarified that all size references in the law refer to interior livable space — not overall building footprint.
ADU minimum: State law sets a floor at 150 square feet for efficiency units. Practically, most Peninsula ADUs are 400 to 1,000 square feet — smaller units don’t justify the fixed costs of a kitchen and bathroom, and larger units maximize rental income.
How Many Per Lot
Single-family lot: One attached ADU plus one detached ADU, plus one JADU. The 2025 legislation SB 543 codified this allowance, clarifying HCD’s prior guidance. This means a single-family homeowner could theoretically have three additional units on one lot: an attached ADU, a detached ADU, and a JADU. In practice, lot size and setbacks on the Peninsula typically support one ADU (detached or attached) plus one JADU.
Multifamily property: One ADU per existing unit, up to eight ADUs total (under SB 1211, effective 2025). Plus up to 25 percent of existing units as converted interior ADUs.
Owner-Occupancy — Do You Need to Live There?
ADUs: No owner-occupancy requirement. AB 976 (effective January 1, 2024) permanently eliminated the owner-occupancy requirement for ADUs. You can build an ADU and rent it while living in the primary home, or rent both the ADU and the primary home, or live in the ADU and rent the primary home. You do not need to be an owner-occupant.
JADUs: Relaxed requirements. Historically, JADU creation required the owner to occupy either the JADU or the primary home. AB 1154 (effective January 1, 2026) relaxes this requirement: if the JADU has its own separate sanitation facilities (its own bathroom), no owner-occupancy is required. This is a meaningful change for homeowners who want to create a JADU in a home they don’t occupy — previously, this was prohibited.
Short-term rentals. State law requires that ADUs be rented for terms longer than 30 consecutive days. No Airbnb-style nightly rentals. AB 1154 extended this same 30-day minimum rental term requirement to JADUs, effective January 2026. Some Peninsula cities (including San Francisco) have additional short-term rental regulations that may impose further restrictions.
Parking — The Rule That Changed Everything
State law eliminated the biggest barrier to garage conversion ADUs: you do not need to provide replacement parking when you convert a garage to an ADU.
Before this change, homeowners who wanted to convert a two-car garage to an ADU were required to build two new parking spaces on their lot — which, on a 25-foot-wide San Francisco lot or a 4,000 square-foot Daly City lot, was physically impossible. The parking requirement effectively prohibited garage conversions in the densest neighborhoods.
Now, the parking is simply gone. You convert the garage, and the city cannot require you to replace the spaces.
For detached and attached ADUs: No additional parking is required if the ADU is within half a mile of public transit. On the Peninsula, most properties near BART (Daly City, Colma, South San Francisco, San Bruno, Millbrae stations), Caltrain (all stations from San Francisco to San Mateo), or frequent bus routes qualify for this exemption. For properties farther from transit, cities can require up to one parking space per ADU — but not more.
Pre-Approved ADU Plans
AB 1332 (effective January 2025) required every California city to establish a pre-approved ADU plan program. The idea: the city pre-reviews a set of ADU designs so that homeowners using those designs skip most of the plan-check process, and permits are issued faster.
How it works in practice on the Peninsula: Pre-approved plans are available from most Peninsula cities, but “pre-approved” doesn’t mean “pre-fitted to your lot.” A pre-approved plan assumes a standard flat lot with standard setbacks and standard utility locations. If your lot has a slope, an unusual setback condition, a utility easement, or access constraints — common on the Peninsula — the pre-approved plan needs modification. Those modifications require plan review, which narrows the time savings.
Flat lots with straightforward setbacks, standard utility access, and a homeowner who is comfortable with one of the available designs. The permitting process can be shortened by two to four weeks.
Hillside lots, irregular lots, lots with easements or access constraints, homeowners who want a specific layout or finish level, or situations where the ADU must be carefully positioned to maximize yard space or privacy.
Most of ACI’s Peninsula ADU projects use custom designs because the lot conditions demand it. ACI’s design-build model bundles design into the project contract. Whether you use a pre-approved plan (adapted to your lot) or a custom design, the design cost is part of the project — not a separate architectural fee you pay before learning whether the project is feasible.
Separate Sale — AB 1033 and What It Means
AB 1033 (effective January 1, 2024) allows local jurisdictions to permit the separate sale of an ADU as an individual condominium unit. San Francisco has opted in. Other Peninsula cities are evaluating the provision.
What this means: If your city has opted in, you may be able to sell your ADU separately from your primary home — effectively creating two properties on one lot. The ADU would be sold as a condo unit with its own title, its own financing, and its own owner.
The practical reality (as of early 2026): This is still early-stage. The implementation details — condo mapping, CC&Rs, shared-infrastructure agreements (what happens when the ADU’s sewer lateral runs under the primary home’s yard?), and lender willingness to finance a backyard condo — are being worked out. Few ADU condo sales have closed on the Peninsula to date.
What it means for planning: Even if you don’t plan to sell the ADU separately today, building with AB 1033 in mind — separate utility metering, independent systems, clearly defined property boundaries, and a structure that meets condo-quality construction standards — preserves the option for the future. It costs little to nothing extra during construction and could be significant at eventual disposition.
Coastal Zone ADUs — What's Different on the Coastside
Parts of Pacifica (Sharp Park, Rockaway Beach, portions of Linda Mar near the coast) and all of Half Moon Bay and the unincorporated coastside fall within the California Coastal Zone, where the Coastal Act adds an additional permitting layer.
Before 2026: ADUs in the Coastal Zone required a Coastal Development Permit (CDP) in addition to the standard building permit. The CDP process was not subject to the 60-day ADU approval timeline and could be appealed to the California Coastal Commission — adding months or years to the process.
After AB 462 (effective October 2025): Coastal development permit applications for ADUs must now be approved or denied within 60 days, the same timeline as standard ADU applications. The CDP process must occur concurrently with the local planning/building permit. And for certain counties affected by disaster emergencies (including Los Angeles County), ADUs are fully exempt from the CDP requirement.
Peninsula impact: For Pacifica homeowners in the Coastal Zone, this is a meaningful improvement. The CDP no longer represents an open-ended timeline risk. The 60-day shot clock now applies to both the building permit and the coastal permit, processed concurrently. For Sharp Park and Rockaway Beach homeowners who previously faced uncertainty about CDP timelines, this removes a significant planning barrier.
Impact Fees and School Fees
ADUs of 750 square feet or less are exempt from most local impact fees. Above 750 square feet, fees are proportional to the ADU’s size relative to the primary dwelling. The 2025 legislation SB 543 clarified that the 750 SF threshold refers to interior livable space.
ADUs and JADUs of 500 square feet or less of interior livable space are exempt from school impact fees under Education Code §17620. SB 543 (signed October 2025) clarified that this threshold refers to interior livable space. For larger ADUs, school fees may apply at the local rate.
State law prohibits cities from charging utility connection fees for ADUs built within an existing structure (garage conversions, JADUs). For new construction ADUs (detached and attached), connection fees may apply but must be proportional to the ADU’s impact on the utility system.
ADU Amnesty — Legalizing Unpermitted Units
AB 2533 (effective January 2025) extended the amnesty deadline for unpermitted ADUs built before January 1, 2020. If you have an existing unit — a converted garage, a finished basement apartment, an in-law suite — that was built without permits, you may be able to legalize it through the amnesty program.
How It Works
You apply to your city to bring the existing unit into compliance. The city evaluates the unit for health and safety standards — electrical, plumbing, egress, fire safety — and identifies what needs to be corrected. You make the corrections, pass inspections, and receive a permit. The process is designed to be less punitive than standard code enforcement.
What Typically Needs Fixing
Electrical brought to current code (GFCI protection, proper circuits, grounded outlets). Plumbing inspected and corrected (proper drainage, hot water, ventilation). Egress windows in sleeping areas. Smoke and CO detectors. Fire-rated separation from the primary home if attached. Many unpermitted units need $15,000 to $50,000+ in work to meet current standards — but the alternative is a unit that’s both illegal and potentially unsafe.
The Value of Legalizing
A permitted ADU adds to your property’s appraised value. An unpermitted unit does not — and may be flagged as a liability during a sale. Legalizing the unit also protects you from code enforcement action and gives your tenants legal protections they don’t have in an unpermitted space.
ACI handles the construction work needed to bring unpermitted units into compliance. We assess the unit, identify what needs to be corrected, prepare plans for the permit application, and perform the construction to pass inspections.
How These Laws Interact With Peninsula Cities
State law sets the floor — the minimum rights you have as a homeowner. Local ordinances can be more permissive than state law but cannot be more restrictive. If a local ordinance conflicts with state law, state law controls.
That said, the practical experience of permitting an ADU varies by city because each city administers the process through its own building and planning departments, with its own staffing levels, its own fee schedules, and its own interpretation of how state law applies to local conditions.
Pacifica
Community Development Department, 1800 Francisco Boulevard. Reduced walk-in hours through early 2026. Coastal Zone overlay in Sharp Park and Rockaway Beach adds CDP layer (now with 60-day timeline under AB 462). Hillside Preservation District in Pedro Point adds design review for exterior changes on hillside lots.
San Francisco
DBI (building) + SF Planning (zoning). Two-agency process that takes longer than Peninsula single-agency cities. SF has opted in to AB 1033 (separate ADU sale). Mandatory soft-story retrofit program has been applied to qualifying multi-family buildings. Permitting timelines are longer than Peninsula cities — budget 3 to 6+ months for the full permitting cycle.
Daly City
Planning Division (650) 991-8033, Building Division (650) 991-8061. Processing times currently longer than normal due to high application volume. Doelger split-level lots (25–30 ft wide) make garage conversion the most common ADU path.
South San Francisco, San Bruno, Millbrae, Burlingame, San Mateo
Standard building department processing. Each city has its own ADU ordinance implementing state law — fee schedules, processing timelines, and local interpretations vary. We know the specific requirements in each city and submit accordingly.
What These Laws Mean for Your Project
The legal framework is firmly on your side. California has systematically removed the barriers that used to make ADU construction difficult or impossible: eliminated parking requirements, reduced setbacks, mandated ministerial approval, capped processing timelines, expanded height allowances near transit, removed owner-occupancy requirements, and created the potential for separate sale.
What the laws don’t do is build the ADU. The permitting process still requires a complete, code-compliant application — architectural plans, structural engineering, Title 24 energy compliance, and the specific documentation each city requires. The construction still requires a licensed contractor who understands Peninsula lot conditions, building codes, and the practical challenges of building on hillside lots, in fog corridors, and on 1950s-era infrastructure.
ACI handles both. We navigate the regulatory landscape and build the physical structure — under one contract, with one team. If you’re ready to take advantage of these laws, we’ll help you understand exactly what’s possible on your specific property.