Redwood City ADU Regulations & Zoning
When do Redwood City ADU regulations apply?
Planning an Accessory Dwelling Unit (ADU) starts with knowing what's possible on your property. Here's a quick snapshot of the key build guidelines and permitting details to help you move forward with clarity.
You can build an ADU up to 850 square feet for a one-bedroom unit, or 1,000 square feet for two or more bedrooms, with 4-foot setbacks from the side and rear property lines. Detached ADUs can reach 16-18 feet in height depending on design. Your ADU must maintain a minimum 6-foot separation from other structures.
Permitting typically takes 2 to 3 months. Starting May 2025, homeowners must complete a brief survey about their ADU to finalize building permits.
What Are the Rules for ADUs in
Redwood City
?
Number of ADUs Allowed
On single-family residential lots in Redwood City, you can build one ADU (attached or detached) and one Junior ADU (JADU). There is no minimum lot size requirement.
Multifamily properties can convert uninhabited spaces (including garages) into ADUs—at least one ADU or up to 25% of existing units. Plus, up to two detached ADUs with 4-foot setbacks are also allowed.
Yes, Redwood City allows Junior ADUs up to 500 square feet. A JADU must be within the existing or proposed single-family residence. JADUs require a separate entrance and an efficient kitchen. Owner-occupancy is required for properties with JADUs.
Redwood City does not have a separate guest quarters classification. Any secondary living space with kitchen facilities would be classified as an ADU.
ADU Size Limits
Detached ADUs are limited to 850 square feet for a one-bedroom unit, or 1,000 square feet for units with two or more bedrooms. ADUs up to 800 square feet with 4-foot setbacks and 16-foot height qualify for streamlined approval.
Attached ADUs are limited to 850 square feet or 50% of the primary dwelling's floor area (whichever is greater), with a maximum cap of 1,000 square feet.
Yes. Under California state law, ADUs up to 800 square feet are exempt from lot coverage, FAR, and open space requirements. This ensures you can build a qualifying ADU even if your lot is otherwise at maximum coverage.
About MolaADU
This page offers a clear summary of what’s allowed—how many ADUs you can build, size limits, setbacks, and other key requirements. But we go beyond the basics. Our insights are grounded in real-world experience, not just recycled bullet points.
Whether you're planning a rental unit, a guest house, or a space for multigenerational living, we’re here to help you move forward with clarity and confidence.
Height & Setbacks
Detached ADUs are limited to 16 feet for a studio-style unit with a sloped roof. Other designs can reach up to 18 feet. Conversion ADUs have no height limit since they use existing structures.
Limited two-story configurations may be possible within the 18-foot height limit. Full two-story ADUs are generally not permitted as detached structures. Consult with the city for specific designs.
Detached ADUs require minimum 4-foot setbacks from side and rear property lines, plus at least 6 feet from existing structures. Front setbacks follow the underlying zoning district requirements. No setback is required for an ADU replacing an existing structure in the same location and dimensions.
Redwood City requires detached ADUs to be at least 6 feet from the primary residence and any other existing structures on the lot.
Permitting & Timeline
Redwood City processes ADU permits efficiently with a streamlined process. Expect 2-3 months from complete application to permit issuance. The city is required to review permit applications within 60 days.
Permit costs range from $5,000 to $10,000 depending on project scope. No impact fees are charged on ADUs less than 750 square feet. Contact the Planning Division to verify current fee schedules.
Redwood City does not routinely require soils reports for standard ADU projects. If your property is on septic, San Mateo County Environmental Health will need to review capacity. Properties near creeks or with steep slopes may have additional requirements.
Parking Requirements
No additional parking is required for ADUs in Redwood City. This applies even when converting a garage to an ADU—replacement parking is not required. Proximity to Caltrain and local shuttles means most properties would also qualify for transit exemptions.
No. When converting a garage or carport to an ADU, replacement parking is not required under California state law.
Since no parking is required, this is generally not a concern. If you choose to provide parking voluntarily, it can be located anywhere on the property that meets city standards.
ADU Costs & Rental Income
The total cost to build an ADU in Redwood City typically ranges from $200,000 to $400,000 depending on size and design. Permits and fees run $5,000-$10,000. Utility connection fees for water, sewer, and electricity can add $10,000-$20,000. Construction costs range from $200-$500 per square foot depending on materials and labor.
Redwood City benefits from its central Peninsula location and Caltrain access. Based on current market data: Bedrooms Average Rent Studio $2,000 - 2,300 1 Bedroom $2,400 - 2,700 2 Bedroom $3,000 - 3,400 3 Bedroom $3,700 - 4,100 Actual rents vary by neighborhood and proximity to downtown or transit.
Several factors impact your total ADU cost: lot conditions, design complexity, utility upgrades, and finish level. Eco-friendly materials and energy-efficient appliances are encouraged and may qualify for rebates.
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