The Complete San Mateo ADU Requirements Guide
If you’re thinking of building an accessory dwelling unit (ADU) in San Mateo, it’s important to learn the regulations. Thanks to a series of state laws promoting ADU construction in California, building an ADU in San Mateo is a straightforward process.
An ADU is a self-contained living unit that shares a lot with a larger main residence. Whether used to earn rental income, house family, or create a home office, ADUs add value to your lot.
Read on to learn everything you need to know about the requirements for building an ADU in San Mateo and how Samara can make the construction process even easier.
San Mateo ADU regulations at a glance
The city of San Mateo is obligated to review your ADU permit submission within 60 days. You can expect the full permitting process to take three to four months from your first submittal date. Here’s what you need to know as you plan your ADU:
Size and lot requirements
Size regulations for ADUs in San Mateo vary based on the Floor Area Ratio (FAR) required by your property’s zoning district. While 800-square-foot ADUs are permitted citywide, larger units must conform to the standards of your specific zoning district.
- Detached ADUs: One-bedroom detached ADUs can reach 850 square feet, while two-bedroom detached ADUs can be to 1,000 square feet. The height limit is 16 feet to the top of the plate line and 24 feet to the roof peak.
- Attached ADUs: An ADU conversion within the walls of an existing primary dwelling or accessory structure is not subject to size regulations. The maximum height is 24 feet to the top of the plate line and 32 feet to the roof peak.
- Junior ADUs are capped at 500 square feet.
Additionally, all San Mateo ADUs should have setbacks of at least four feet from the rear and side yard property lines.
Design requirements
San Mateo ADUs are required to comply with specific design standards. All ADUs require careful window placement: windows must be offset from neighboring properties’ windows, and any second-story windows within five feet of a residential lot line require obscured glazing.
For visual cohesion, attached ADUs must match the architectural style of the structure they are attached to, using similar building materials, finishes, and paint colors.
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Parking requirements
All ADUs in San Mateo require one off-street parking space. It can be located anywhere on the site, including your driveway or setback areas. The parking requirement can be waived if you live within a half mile of a public transit stop or in a historic district. JADUs do not require parking.
Zoning eligibility
ADUs in San Mateo can be constructed on any residentially zoned property, whether single- or multi-family. JADUs are not allowed on mixed-used properties.
Number of ADUs allowed
On single-family properties, one ADU is allowed per lot.
For multi-family properties, up to eight detached ADUs are allowed. Non-residential spaces, such as storage areas or offices, can be converted into ADUs as long as the total number of conversions is not greater than 25 percent of the existing unit count.
Meet the KurodasStreamline your ADU in San Mateo
If you’re looking to build an ADU, Samara makes it easy. We handle everything from permits to installation, including ADU financing options. Call us at 650-420-2607 to schedule a 15-minute consultation and discover how simple adding a Backyard ADU can be.
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