Can I build an ADU in Woodside, California?
Yes. Woodside approves ADUs ministerially, within 60 days of a complete application. The Town's table allows one ADU plus one junior ADU on lots under 1 acre and up to four units in total on lots of 1 acre or more, though state law may allow more on smaller lots. Attached or detached ADUs can be up to 1,500 sq ft (attached ones are also capped at 50% of the house), and rentals must be at least 30 days.
| Units allowed, lot under 1 acre | 1 ADU + 1 junior ADU [1] |
| Units allowed, lot 1 acre or more | Up to 4 total (no more than 3 ADUs; a 4th if one is a JADU) [1] |
| Max size, detached ADU | 1,500 sq ft (including any attached garage) [2] |
| Max size, attached ADU | 50% of the main residence or 1,500 sq ft, whichever is less [3] |
| Side/rear setback, new ADU | As little as 4 ft (only one unit per lot) [4] |
| Parking | 1 space per ADU with a bedroom; none for studios [5] |
| Review | Ministerial, Planning Director decides within 60 days [6] |
| Minimum rental term | 30 consecutive days [7] |
| Junior ADU | Up to 500 sq ft inside the house; owner-occupancy required [8] |
How many units
The number of ADUs and junior ADUs (JADUs) depends on lot size [1]. On lots under 1 acre in the R-1, SR, RR and SCP districts, you can have one ADU (attached or detached) plus one JADU. Lots of 1 acre or more can have up to four units in total. No more than three of them can be ADUs, and a fourth unit is allowed only if one is a JADU. An existing barn or stable can also be converted to an ADU under its own standards. State law (Gov. Code §66323) already requires cities to allow a converted ADU, a JADU and a new detached ADU of up to 800 sq ft on a single-family lot, so state law may override the one-ADU limit on lots under 1 acre. Starting January 1, 2027, AB 956 will require approval of two new detached ADUs on a single-family lot.
Size, height and setbacks
A detached ADU can be up to 1,500 sq ft, counting any attached garage [2]. An attached ADU is capped at 50% of the main residence or 1,500 sq ft, whichever is less [3]. A new ADU can sit as close as 4 ft to the side and rear property lines [4], but only one unit per lot can use the 4-ft setback. Any part of an ADU inside the normal setbacks is limited to 800 sq ft. Otherwise, the Town's accessory-building rules apply. One detached ADU of 800 sq ft or less that is 16 ft tall or less is exempt from the plate-height rules. Converting an existing garage or accessory structure needs no new setback.
Parking and review
You need one parking space for an ADU with one or more bedrooms and none for a studio [5]. Parking is waived near transit, for conversions of existing space, and in a few other cases. The Planning Director reviews ADU plans ministerially and must approve or deny them within 60 days of a complete application [6]. Neighbors are notified when you use a setback exception, but there are no appeal rights.
Renting and junior ADUs
An ADU that is rented can't be rented for less than 30 consecutive days [7]. A JADU is up to 500 sq ft, sits entirely inside the main house, and has an efficiency kitchen and its own exterior entry [8]. The code requires owner-occupancy in any home with a JADU [8], and it lets a JADU have its own bathroom. State law allows owner-occupancy to be required only when the JADU shares a bathroom with the house, so state law may override this provision for a JADU with its own bathroom.
See how Woodside compares with 8+ other California towns on accessory dwelling units (adus) →
Next steps
- Meet with a Town planner at Town Hall (2955 Woodside Road, 650-851-6790) to confirm how many units your lot size allows and whether setback or slope exceptions apply.
- Consider a design from the Town's pre-approved detached ADU plans list for a faster review.
- Submit a building permit application with site plan, floor plans and floor-area calculations; septic feasibility may be needed if you are not on sewer.
- Expect a ministerial decision within 60 days of a complete application; neighbors are notified if you use a setback exception.
Common questions
- Can I build an ADU in Woodside, California?
- Yes. Woodside approves ADUs ministerially, and the Planning Director must approve or deny plans within 60 days of a complete application. Lots under 1 acre can have one ADU plus one junior ADU, though state law may allow more, and lots of 1 acre or more can have up to four units in total.
- How big can an ADU be in Woodside, California?
- A detached ADU can be up to 1,500 sq ft, counting any attached garage. An attached ADU is capped at 50% of the main residence or 1,500 sq ft, whichever is less. A junior ADU is up to 500 sq ft inside the main house.
- What are the ADU setbacks in Woodside, California?
- A new ADU can sit as close as 4 ft to the side and rear property lines, but only one unit per lot can use the 4-ft setback, and any part inside normal setbacks is limited to 800 sq ft. Converting an existing garage or accessory structure needs no new setback.
- Does an ADU need parking in Woodside, California?
- An ADU with one or more bedrooms needs one parking space, and a studio needs none. Parking is waived near transit, for conversions of existing space and in a few other cases.
- Can I rent my ADU on Airbnb in Woodside, California?
- No. A rented ADU in Woodside can't be rented for less than 30 consecutive days.
California's statewide ADU law
California's ADU law (Gov. Code §§66310–66342, recodified from §65852.2; latest amendments effective January 1, 2026) overrides conflicting city rules, including in charter cities. Cities must approve ADUs ministerially (no hearing) within 60 days of a complete application, or the permit is deemed approved.
What cities cannot require or do:
- Owner-occupancy for an ADU.
- A minimum lot size.
- Side or rear setbacks over 4 feet for a new ADU, or any setback for a converted existing structure.
- Size, lot coverage or floor-area rules that block an ADU of at least 800 sq ft. Size caps can't be under 850 sq ft (1,000 for 2+ bedrooms).
- Parking within half a mile walking distance of public transit, or replacement parking for a garage converted to an ADU.
- Impact fees on ADUs of 750 sq ft or less.
By right on a single-family lot: one converted ADU plus one junior ADU (JADU, up to 500 sq ft inside the house), plus one new detached ADU (up to 800 sq ft, 16 ft tall). Owner-occupancy may be required only for a JADU that shares a bathroom.
Short-term rentals: cities may bar ADU rentals under 30 days, and must for by-right ADUs, JADUs and SB 9 units.
Coming January 1, 2027: AB 956 raises the by-right count to two new detached ADUs per single-family lot.
SB 9 (§§65852.21, 66411.7) allows two homes on a single-family lot, or a split into two lots of at least 1,200 sq ft (with a 3-year owner-occupancy affidavit).
What the ordinance says
- Sec. 153.211(A)(5), Table L-1, Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
A maximum of four accessory dwelling units and junior accessory dwelling units total as follows: • No more than three accessory dwelling units may be attached to, or detached from the main dwelling . • A fourth accessory unit may be allowed if at least one of the four total units is a junior accessory dwelling unit.
- Sec. 153.211(A)(7), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
The floor area of a detached accessory dwelling unit , including the floor area of any attached garage, shall not exceed 1,500 square feet.
- Sec. 153.211(A)(6), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
The floor area of an attached accessory dwelling unit shall not exceed 50 percent of the size of the main residence, including the accessory dwelling unit , or 1,500 square feet, whichever is less.
- Sec. 153.211(A)(4)(a)(1), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
New detached accessory dwelling units may have a side and/or rear setback of no less than four feet from the side and rear property lines.
- Sec. 153.211(A)(2)(a), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
Parking requirements for accessory dwelling units shall be one parking space per accessory dwelling unit that has one or more bedrooms. No parking spaces shall be required for units that do not have a separate bedroom, such as a studio accessory dwelling unit .
- Sec. 153.211(A)(3), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
All plans for accessory dwelling units shall be subject to ministerial review and approval or denial by the Planning Director within 60 days of receiving a complete application.
- Sec. 153.211(A)(9), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
Accessory dwelling units which are rented shall not be rented for less than 30 consecutive days.
- Sec. 153.211(C)(2), Municipal Code Ch. 153 Zoning, §153.211 Accessory Dwelling Units (incl. barn/stable conversions, JADUs)
Owner-occupancy is required in any residence that contains a junior accessory dwelling unit . The owner may reside in either the remaining portion of the structure or in the newly created junior accessory dwelling unit .