California ADU rules · San Mateo County
Can I Build an ADU in Woodside?
Yes — you can build an ADU in Woodside. California's statewide ADU law requires every city, including Woodside, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local rule1 ADU (attached or detached) + 1 JADU per lot
Explicitly allows 1 ADU and 1 JADU per single-family lot.
Units on a multifamily lot
Local ruleUp to 3 ADUs (attached or detached) plus 1 JADU (total 4 units if at least one is a JADU); state minimums for conversions and detached ADUs also apply
Local cap of 3 ADUs + 1 JADU; state minimums for conversions and detached ADUs still apply.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,500 sq ft
Detached ADU max size is 1,500 sq ft including attached garage.
Max attached ADU size
Local rulelesser of 50% of main residence (including ADU) or 1,500 sq ft
Attached ADU limited to 50% of main residence or 1,500 sq ft, whichever is less.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
CA state law16 ft
16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.
Setbacks
Side setback
Local rule4 ft
4 ft side setback for new ADUs; conversions of existing structures may have no new setback.
Rear setback
Local rule4 ft
4 ft rear setback for new ADUs; conversions of existing structures may have no new setback.
Front setback
Local ruleMust comply with standard front setback for the zone (e.g., R-1: 30 ft; SR/RR/SCP: 50 ft)
Front setback per base zone; cannot preclude state-mandated ADU.
Separation from main house
Local ruleNone required
No local minimum separation; only building/fire code applies.
Parking
Parking required
Local ruleUp to 1 space
1 space per ADU with a bedroom; none for studios; state exemptions apply.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
Local ruleBuilding permit, Demolition permit (if applicable)
Ministerial building permit required; demolition permit if converting/demolishing existing structure.
Woodside-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Very High Fire Hazard Severity Zone (VHFHSZ)
ADUs not required to provide sprinklers if not required for primary residence; alternative fire protection allowed.
Hillside/Slopes >35%
ADUs may be allowed on slopes >35% but <50% if infeasible elsewhere, subject to additional review.
Woodside allows detached ADUs up to 1,500 sq ft (including garage) and up to 3 ADUs plus 1 JADU on multifamily lots, with nuanced height rules and hillside/fire zone considerations. Front setbacks follow base zoning, and parking is required for ADUs with bedrooms unless exempted by state criteria.
Frequently asked questions
Can I build an ADU in Woodside?
Yes. California's statewide ADU law requires Woodside to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Woodside?
A detached ADU of at least 1,500 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Woodside?
Side and rear setbacks are limited to 4 ft. Must comply with standard front setback for the zone (e.g., R-1: 30 ft; SR/RR/SCP: 50 ft).
Is parking required for an ADU in Woodside?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Woodside?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Woodside?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Woodside Municipal Code, Chapter 153.211 (Accessory Dwelling Units), Ord. No. 2025-647 (amended May 8, 2025)
- WMC 153.211(D)(1)
- WMC 153.211(D)(2)
- WMC 153.211(E)(1)
- WMC 153.211(E)(2)
- WMC 153.211(G)(1)
- WMC 153.211(G)(2)
- WMC 153.211(G)(3)
- WMC 153.211(H)(1)-(2)
- WMC 153.211(I)
- WMC 153.211(J)(1)
- WMC 153.211(J)(2)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66314 (local ordinance standards)
- Cal. Gov. Code § 66315 (owner-occupancy)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Woodside's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Woodside Planning before relying on it.
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