National City, CA Building Setbacks & Zoning: Lot Coverage Limits (2026)

National City Municipal Code § 18.21.040 sets residential development standards in Table 18.21.040, and its row for maximum lot coverage prints 75% in RS-1, RS-2, RS-3, RM-1, RM-2 and RM-3. The RS-4 column prints N/A. The RS-4 zone is the small lot single-family zone tied to the Westside Specific Plan, and § 18.20.020(E) says lands within an adopted specific plan are governed by that plan's zoning regulations, with the Land Use Code filling any development standard the plan is silent on.

The section prints coverage as a percentage of the lot. It does not print a separate impervious surface figure, so 75% is the number the table gives. Lot size feeds the calculation: minimum lot area is 10,000 SF in RS-1, 5,000 SF in RS-2, RS-3, RM-1, RM-2 and RM-3, and 2,500 SF in RS-4. Maximum density is one dwelling unit per lot in RS-1 and RS-2, one per 2,900 SF of lot area in RS-3, one per 2,500 SF in RS-4, one per 1,900 SF in RM-1, one per 900 SF in RM-2 and one per 580 SF in RM-3.

Accessory buildings carry their own cap. In RS-1, RS-2 and RS-3 the total area of accessory structures is 10% of lot size, excluding up to 400 SF of covered parking and area dedicated to an ADU. The RS-4, RM-1, RM-2 and RM-3 columns print None. Note (d) adds that no single accessory structure can have a footprint greater than half of the primary structure, again excluding area dedicated to an ADU. The same table sets the number of detached buildings at 3 per full 5,000 ft2 of lot area in RS-1, RS-2 and RS-3, and 3 in the other columns printed for that row.

Usable open space is a separate test. The table prints N/A for RS-1 through RS-4 and points the RM zones to Section 18.41.040. Anyone who cannot meet the 75% figure has two paths in Title 18: a variance under § 18.12.120, decided by the planning commission after a public hearing, or a planned development permit under § 18.12.130, which is limited to sites of not less than one acre under one ownership.