San Mateo R3 zoning: height, setbacks and lot size

R3 (Multiple Family Dwellings (Medium Density)) is a zoning district in San Mateo. Every value below was read from the San Mateo Municipal Code and links to its section (read October 2026). State laws such as the ADU and SB 9 rules can allow more on a residential lot. General information, not legal advice — read the code text and check with the city before you build.

The general rule for a typical lot in this zone. Zoning tables often attach notes, such as rules for corner lots, lots next to a residential zone, or new subdivisions only. Open “code text” under a value to see the table cell or sentence it was read from.

The code sets other values for particular lots, buildings or locations in R3:

• Minimum front setback: 1/2 the building height — For buildings exceeding three stories in height, unless a smaller setback is allowed in a special use permit. § 27.22.070
• Minimum front setback: the building height or 15 ft, whichever is greater — On a parcel developed for multiple-family use when the front abuts an R1 or R2 zoned parcel. § 27.22.070
• Minimum front setback: 10 ft — Along El Camino Real frontage for properties from Ninth Avenue south to the City limits developed with buildings over two stories in height. § 27.22.095
• Minimum side setback: 1/2 the building height, max 25 ft — For multiple-family dwelling structures more than two stories in height. § 27.22.080
• Minimum side setback: 1/2 the building height or 15 ft, whichever is greater — On the side abutting an R1 or R2 zoned parcel. § 27.22.080
• Minimum side setback: 10 ft — For a nonresidential building on a parcel improved pursuant to a special use permit, exclusive of residential accessory buildings. § 27.22.080
• Minimum side setback: 1/2 the building height or 15 ft, whichever is greater — For a nonresidential structure more than two stories in height on a parcel improved pursuant to a special use permit. § 27.22.080
• Minimum rear setback: 1/2 the building height, max 25 ft — For buildings more than three stories in height, unless a greater dimension is required as a condition of approval for a special use permit. § 27.22.090
• Minimum rear setback: the building height — When a parcel zoned for multiple-family use abuts an R1 or R2 zoned parcel. § 27.22.090
• Maximum floor area ratio (FAR): 1.0 — With zoning administrator permission under special-use procedures; additional floor area must satisfy the stated conditions. § 27.22.050

We did not find a general height, stories, lot size, lot coverage, density limit for R3 in the zoning tables we read. The code may still set one elsewhere — check the San Mateo Municipal Code.

• R1-A