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Building an ADU in Redwood City, CA

Checked against the city's ADU pages on Oct 18, 2026.

Can I build one?
Yes, up to 1,200 sq ft The August 2026 handout allows 1,200 sq ft with 2+ bedrooms and 850 sq ft for a studio or 1 bedroom. No parking required.[1]
What will the city charge?
$5,322 Base permit fee, new ADU 601 to 800 sq ft. School and utility fees extra. See every fee[2][3]
Who builds here?
8 licensed builders Each lists Redwood City on its own site and holds an active CSLB license. See the list
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Licensed ADU builders in Redwood City

Ranked by a public score anyone can check: license, years licensed, ADU types and cities shown on their own sites, a local office, and published prices. Nobody pays to move up. Quote requests go to our team with the builder you picked. How we rank

What Redwood City allows

  • Detached ADU, max size[1]

    850 sq ft for a studio or 1 bedroom; 1,200 sq ft with 2+ bedrooms

  • Attached ADU, max size[1]

    50% of the existing home

  • Junior ADU (inside the house)[1]

    Up to 500 sq ft, plus up to 150 sq ft for an entrance. R-1 and RH zones only

  • Height[1]

    Detached: 16 ft; 18 ft (+2 ft for roof pitch) within 1/2 mile of a major transit stop; 18 ft on a multifamily lot. Attached: up to the zone's limit

  • Side and rear setbacks[1]

    4 ft side and rear for new construction; a conversion keeps the existing setbacks

  • Lot coverage and open space[1]

    Zone rules apply, but they can't stop an 800 sq ft ADU

  • Units on a single-family lot[1]

    1 detached ADU + 1 converted ADU + 1 JADU

  • Parking[1][3]

    None for ADUs or JADUs

  • Owner must live on site[1]

    No for an ADU. For a JADU only if it shares a bathroom with the house
  • The city's ADU web page still lists 1,000 sq ft for a detached ADU with more than one bedroom. The August 2026 handout says 1,200 sq ft. Confirm with Planning before you design.[3][1]
  • Minimum size is 150 sq ft. Rentals under 30 days are not allowed for ADUs or JADUs.[1]
  • A new detached ADU needs a fire flow test to show enough water supply; lead time is several weeks. Sprinklers may be required if the house has them.[3][1]
ADU rules in Redwood City drawn on a typical lot Detached ADU, city handout (Aug 2026): up to 1,200 square feet, 4 feet from side and rear lot lines, 16 feet tall. Parking: None required. Rear lot line Street Main house ADU up to 1,200 sq ft 16 ft tall 4 ft 4 ft Parking: none required
Detached ADU, city handout (Aug 2026). Not to scale.

City fees for an ADU in Redwood City

Fee lines for an ADU in Redwood City
Base permit fee, new ADU $3,999.53 up to 400 sq ft or a garage conversion; $4,660.62 for 401 to 600 sq ft; $5,321.71 for 601 to 800 sq ft[2][3] Valuation-based fees are added case by case.
Transportation, park and housing impact fees $0 for ADUs[2][4][5][3] A council resolution exempts ADUs from these three fees until April 1, 2027. The ADU page also says no impact fees under 750 sq ft.
School fees $5.17 per sq ft, split between Sequoia Union HSD and your elementary district[4][6][7] For 500 sq ft or more of living space. You write two checks.
Wastewater collection capacity fee (City of Redwood City) $1.78 per sq ft[2] The wastewater treatment capacity fee does not apply to ADUs.
Water capacity fee (City of Redwood City) $3.19 per sq ft[2][4] The city says water and sewer capacity fees apply to ADUs.
Address for the ADU $376[2]
School fee rates for districts in Redwood City (2)

Sequoia Union HSD collects the fee together with your elementary district and keeps 40%. The rate shown is the combined total.[6][7]

  • Redwood City School District[7][6]Combined fee with Sequoia Union HSD, paid in two checks. Under 500 sq ft pays nothing. $5.17/sq ft
  • Belmont-Redwood Shores School District[7][6]Combined fee with Sequoia Union HSD, paid in two checks. Under 500 sq ft pays nothing. $5.17/sq ft
Total cost in Redwood City, fees plus building

How the permit works

  1. 1

    Book a Planning appointment (optional)

    You can book a Zoom appointment with Planning staff online.[3]

  2. 2

    Fill out the ADU Completeness Checklist

    Prepare construction plans and a building permit application along with the checklist.[3]

  3. 3

    Schedule a fire flow test

    Required for a new detached ADU. Book it with the Engineering Department; lead time is several weeks.[3]

  4. 4

    Submit on eTRAKiT

    Upload the plans, application and checklist on the city's online permit site.[3]

  5. 5

    Finish the homeowner survey

    The city requires a short ADU survey before it finals the building permit. Email the confirmation to permits@redwoodcity.org.[3]

Review time: The Building Division lists 4 to 8 weeks for new buildings and 3 to 4 weeks for additions. ADUs are not listed separately.[8]

State deadline: State law gives the city 15 business days to say if your application is complete and 60 days to approve or deny a complete one.[9]

Apply at: eTRAKiT

Preapproved plans

Redwood City pre-reviews designers' model plans, which cuts review to 30 days. HEART of San Mateo County offers free pre-reviewed plans for all-electric detached ADUs.[3]

  • HEART GLADUR plans (free) Studio 400 sq ft; 1 bed 575 or 745 sq ft; 2 bed 800 sq ft

Free download after a user agreement. You still need a site plan, foundation and utility details, a fire flow test and school district notice.

Common questions

How big can an ADU be in Redwood City?

The August 2026 handout allows a detached ADU of 850 sq ft for a studio or 1 bedroom and 1,200 sq ft with 2 or more. The ADU web page still says 1,000 sq ft, so confirm with Planning. A junior ADU is up to 500 sq ft.[1][3]

Do I need parking for an ADU in Redwood City?

No. Redwood City requires no new off-street parking for an ADU or JADU.[1]

How much are ADU permit fees in Redwood City?

Base permit fees are $3,999.53 up to 400 sq ft, $4,660.62 for 401 to 600 sq ft and $5,321.71 for 601 to 800 sq ft, plus valuation-based fees. Water and sewer capacity fees are $3.19 and $1.78 per sq ft, and impact fees are $0 until April 1, 2027.[2][3]

Are there free ADU plans in Redwood City?

Yes. HEART of San Mateo County offers free pre-reviewed plans from a 400 sq ft studio to an 800 sq ft 2-bedroom.[3]

Do I have to live on the property?

Not for an ADU. For a junior ADU, only if it shares a bathroom with the main house.[1]

Nearby cities

What we couldn't confirm

  • The ADU web page (1,000 sq ft) and the August 2026 handout (1,200 sq ft) disagree on the detached size limit for 2+ bedrooms.
  • The impact fee exemption for ADUs ends April 1, 2027 unless the council extends it.
  • No ADU-specific plan review time published.
  • Whether any parcels are served by another sewer agency, or fall in other elementary districts (such as Woodside or Las Lomitas), was not checked.
  • The zoning code chapter for ADUs (Article 37) was not read directly.

Sources

Every fact on this page links to one of these. We read each one on the date shown.

  1. 1. City of Redwood City ADU Handout, effective August 2026: owner occupancy not required for ADUs, JADU only with shared sanitation Checked Oct 18, 2026
  2. 2. City of Redwood City Master Fee Schedule FY2026-27 (effective July 1, 2026): New ADU base fees $3,999.53 / $4,660.62 / $5,321.71 Checked Oct 18, 2026
  3. 3. City of Redwood City ADU page: base fee estimates $3,999.53 (0-400 sq ft or garage conversion), $4,660.62 (401-600), $5,321.71 (601 Checked Oct 18, 2026
  4. 4. City of Redwood City Development Impact Fees sheet, updated July 2026: parks fee ADU $0/sq ft Checked Oct 18, 2026
  5. 5. City of Redwood City 2026 park impact fees: single family $48,601.86/unit Checked Oct 18, 2026
  6. 6. Sequoia Union HSD 60/40 split Checked Oct 18, 2026
  7. 7. Sequoia Union HSD Per-feeder rates incl Checked Oct 18, 2026
  8. 8. City of Redwood City Approximate building plan review times: new buildings 4-8 weeks, additions 3-4 weeks, residential alterations Checked Oct 18, 2026
  9. 9. California Department of Housing and Community Development (HCD) All state ADU/JADU rules used in state_baseline.md (sizes, heights, setbacks, parking, owner-occupancy, JADU, Checked Oct 18, 2026