San Marcos | Zoning Districts

San Marcos, California Zoning Districts: Residential Zones R-1-20 to R-3-6, What Each Allows, Mixed Use Zones and Planned Residential Developments

This page covers the zones of the City of San Marcos in San Diego County. A zone is the set of rules that the City's Zoning Map gives to each lot: which buildings are allowed, how many homes, and how large. The rules are in Title 20 of the San Marcos Municipal Code, which the City Council rewrote with Ordinance 2025-1568 on December 9, 2025. VanPlex read the current Municode edition, Supplement 14 Update 1. Other places named San Marcos, such as the city in Texas, have different codes. The San Marcos overview has the summary of all seven guide pages.

The Zones That Allow Homes

Sources: San Marcos Municipal Code Tables 20.215-3 and 20.215-4, Table 20.215-2, Table 20.200-1 and Tables 20.225-1 and 20.225-2.

Density in San Marcos is counted per gross acre. A gross acre is 43,560 square feet of the whole lot before any land is taken for a street; the code's definition says that "if a street dedication is required, density shall be calculated using the size of the lot prior to the street dedication." Minimum lot sizes are "net area; reciprocal access easements not included", so a shared driveway strip does not count toward the lot minimum.

Section 20.215.020 describes each zone in words. R-1-20 is for "estate and ranch-style homes with associated rural uses" on lots of 20,000 square feet or more. R-1-10 provides "low-density living on large lots." R-1-7.5 is "intended for traditional subdivision layouts on lots of 7,500 square feet or greater." R-2 provides "low-density, single-family attached homes" and "duplex, 3-unit, and 4-unit buildings that are suitable in massing and character for inclusion in single-family detached neighborhoods." R-3-6 is for "higher-density multifamily attached homes such as apartments, rowhouses, townhomes, motorcourts, and condominiums" at 20.1 to 30 homes per acre, and R-3-10 is for "medium-density multifamily living" at 12.1 to 20 homes per acre "in close proximity to services and bus lines."

By VanPlex arithmetic on those maximums, each home needs this much gross lot area: 21,780 square feet in R-1-20, 10,890 in R-1-10, 7,260 in R-1-7.5 (or 5,445 at 8.0 homes per acre with a PRD), 3,630 in R-2, 2,178 in R-3-10 and 1,452 in R-3-6. The code gives no rounding rule for these numbers, so a 10,000 square foot R-2 lot works out to 2.75 homes. Ask the Planning Division how it treats the fraction before you plan the third home.

What Each Residential Zone Allows

Source: San Marcos Municipal Code Table 20.215-2. P = permitted; A = accessory to a main use; CUP = conditional use permit.

"Permitted" in Table 20.215-2 means the use is allowed if it meets the zone standards, with no special use permit. A conditional use permit is a discretionary permit that the Planning Commission may grant or deny after a public hearing. An accessory use, marked A, is allowed only alongside a main home on the same lot. Section 20.215.040(D) adds that a use not listed in the table "is prohibited", although the Director may allow a use found similar to a listed one.

Note 2 of the table is the main limit in R-2. It applies to multifamily dwellings, supportive housing and transitional housing there, and reads: "Limited to development with detached homes: small lot single-family homes, attached single-family homes, duplexes, and 3-unit buildings and/or 4-unit buildings designed in massing/character to appear as a single-family home, except where modified by a Planned Residential Development." In practice an R-2 project is a set of house-scale buildings of up to four units each, at no more than 12 homes per gross acre. The code defines a multifamily dwelling as a building with "three (3) or more dwelling units", and a duplex as "a building comprised of two (2) attached living units."

The R-1 zones permit single-family detached homes only. More homes on an R-1 lot come through state law: an ADU and a junior ADU under Chapter 20.410, or a second main home or a lot split under SB 9, which San Marcos writes into Chapter 20.470 and Chapter 19.44. The ADUs and SB 9 page covers both. Section 20.300.020(A) says a single-family lot "can include one (1) primary building" and that any added building falls under those two chapters.

Review Steps Built Into the Zones

A permitted use in San Marcos can still need a public hearing. Section 20.215.040(E) says "All attached residential developments, including all projects that comply with the allowed land use and development standards of this chapter, shall be submitted for Site Development Plan Review to the Planning Division." It then sets two tiers:

• Two to nine units in R-2 or R-3. Multifamily Site Development Plan Review "and a Planning Commission hearing."
• Ten or more units in R-2 or R-3. Review "and hearing before the Planning Commission and City Council."
• Mixed use zones. Section 20.225.030(C) requires Site Development Plan Review for all development, and an Area Plan that sets building locations, parking and open space.
• Before applying. Section 20.215.060(A) requires "a pre-application meeting with the applicant/representative and City staff" for R-2 and R-3 projects and attached PRD projects.

The permits and fees page explains who decides and the appeal deadlines. State law may shorten some of these steps for qualifying housing, which the three or more homes page covers.

Mixed Use and Specific Plan Zones

San Marcos has four mixed use zones. Two allow homes. MU-1 has a residential minimum of 20.0 and maximum of 30.0 homes per acre, a floor area ratio of up to 1.75, and buildings of 2 to 4 stories and up to 48 feet. MU-2 allows 30.0 to 45.0 homes per acre, a floor area ratio of 1.75 to 2.25, and up to 5 stories and 60 feet. A floor area ratio is the floor area of the buildings divided by the area of the lot. In both zones the minimum home size is 600 square feet, and the minimum new subdivision lot size is listed as "1,500", with no unit printed. Table 20.225-5 permits multifamily residential on the ground floor and the floors above.

Section 20.225.010 names the places these zones are meant for, including "W. San Marcos Boulevard between S. Rancho Santa Fe Road and Grand Avenue" and "north of State Route 78 from S. Rancho Santa Fe Road east toward Vallecitos De Oro." The MU-1 zone is "intended to define major corridors and transit-proximate locations as mixed use corridors", and it requires pedestrian-oriented ground floor uses along 80 percent of the primary street frontage. MU-3 (SP) and MU-4 (SP) need an adopted specific plan, and Section 20.225.060 states that "residential uses are not permitted in the MU-3 (SP) Zone."

A specific plan is a detailed plan for one area, adopted by the City Council, that replaces the general zone rules there. The Specific Plan Area (SPA) zone in Chapter 20.250 requires one for new development on undeveloped SPA land, normally on at least five acres of contiguous property. Areas already under an adopted specific plan follow that plan's own standards, which this guide did not read. The transitional zones in Chapter 20.235, such as I/MU-1 and L-I/MU-1, mark industrial land planned to move to a mixed use zone later; Table 20.200-1 lists them with densities that "vary."

Planned Residential Developments

The planned residential development, or PRD, is San Marcos's tool for compact housing in any residential zone. Chapter 20.435 says it allows "standard subdivision, alley loaded, cluster or small-lot development, or courtyard site plans." A PRD in a single-family zone needs a conditional use permit; a multifamily PRD goes through Site Development Plan Review. The main rules are:

• No minimum lot per home. "There shall be no minimum area requirement for individual lots, building sites, or dwelling units."
• R-1 density. The whole PRD must equal "the minimum lot size applicable to the Zone, times the number of total dwelling units", and homes must be detached.
• R-2 and R-3 density. Units may not exceed the zone maximum in Tables 20.215-3 and 20.215-4.
• Open space. At least 40 percent of the site, half of it at a finished grade of 10 percent or less.
• Setbacks. 20 feet from the street, 25 feet from the outer boundary of the PRD, and 10 feet between buildings.

The code gives the PRD three density ranges. Section 20.200.020(C) says a PRD in an R-1 zone can reach "a density of one (1) to eight (8) dwelling units per acre." The definition in Chapter 20.600 says "four (4) to eight (8)." Note 2 of Table 20.215-3 says R-1-7.5 density "may increase to maximum of eight (8.0) du/ac. with a PRD." Ask the Planning Division which range applies to your zone.

Where the Code Disagrees With Itself

• R-1-7.5 density. Section 20.215.020(A)(3) says "a maximum density of eight (8) units per one (1) acre"; Table 20.215-3 says 6.0, rising to 8.0 only with a PRD; Table 20.200-1 gives a range of "4.1-8.0 du/ac."
• MU-1 minimum density. Table 20.200-1 gives "20.1-30.0 du/ac"; Table 20.225-1 sets the residential minimum at 20.0.
• R-2 as a single-family zone. Section 20.215.020 lists R-2 under the heading "Single-Family Zones" while Table 20.215-2 permits duplexes and multifamily buildings there. This matters for SB 9, which applies in a "single-family residential zone." Ask the City whether it treats R-2 as one.
• Figures and tables. Figures 20.215-3 and 20.215-4 refer to "Table 20.230-3" and "Table 20.230-4" for residential standards; the residential tables are 20.215-3 and 20.215-4.

Where a table and the text disagree, Section 20.100.090 gives the Director "the responsibility and authority to interpret the meaning and applicability of all provisions." A written interpretation from the Planning Division is the safest basis for a purchase or a design.

Where to Go Next

Related on VanPlex: the San Marcos overview, the California SB 9 page and the California ADU law page.

Frequently Asked Questions

Official sources (checked October 2026)