Modesto | Lots and Subdivisions

Modesto Lot Size and Subdivisions: Minimum Lots, Flag Lots, Parcel Maps, SB 9 and SB 684

Modesto sets lot sizes in Title 10 of its Municipal Code and the rules for dividing land in Title 4, Chapter 4, "Subdivision of Land." To subdivide is to divide one lot into two or more lots that can be sold apart. This page gives the minimum lot area and width in each residential zone, the City's map steps and their fees for FY 2026-2027, and how two state laws, SB 9 and SB 684, apply in a city that has no ordinance of its own for either. The Modesto overview sums up the whole guide.

Minimum Lot Sizes by Zone

Table 4.1-1 in Section 10-4.102 sets the lot rules for the three residential zones. Lot width is "the horizontal distance between the side lot lines measured parallel to the front lot line at any point between the front and rear lot lines" (Section 10-2.149). Lot coverage is the share of the lot under roofs, including patios, porches, garages and covered parking. Driveways, uncovered parking, pools and wood decks do not count toward it (Section 10-2.141).

Source: Modesto Municipal Code Table 4.1-1 and Section 10-4.105, Supplement 72.

The table's first footnote says "Minimum lot size requirements do not apply to the construction of ADUs." In R-1, Section 10-4.103 lets the City ask for a larger lot "where necessary to maintain compatibility with the existing lots of an established neighborhood," using its Neighborhood Compatibility Guidelines. Every lot must also front a street (Section 10-4.111).

Section 10-4.105 allows narrower lots in two cases. On a curved street, such as a cul-de-sac, the front lot line of an R-1 lot may be 40 feet wide if the lot is 50 feet wide from the front setback line to the rear. In R-2 and R-3 those numbers are 50 and 60 feet. A corner R-1 lot on a curve may be 50 feet at the front if it is 60 feet wide behind the setback.

Flag Lots

A flag lot is a lot behind another lot, reached by a narrow strip of land. Section 10-2.142 describes two parts: "the 'flag' (which is the buildable portion of the lot) located generally behind another lot; and the 'flag pole' which provides the only access from the street." Flag lots are one way to add a home behind an existing house on a deep Modesto lot.

Section 10-4.105(c) allows a flag lot "with a minimum width of twenty (20) feet at both the front lot line and front yard setback line" when two findings are made:

• "Creation of the lot(s) will enable use of an existing parcel to permitted density."
• "The existing parcel is of a size and shape that does not allow the creation of standard shaped lots," judged under the Neighborhood Compatibility Guidelines.

Section 10-4.105(d) adds that "No building permit shall be issued for a lot approved under subsection (c) above without a recorded subdivision or parcel map." A flag lot still needs the full lot area of its zone. Five thousand square feet in R-1 means a deep lot of at least 10,000 square feet, plus room for the pole, before a split into a front lot and a flag lot can meet the minimum, by VanPlex arithmetic.

Parcel Maps and Subdivision Maps

Modesto follows the state Subdivision Map Act and adds its own rules. Section 4-4.102 names the Planning Commission as the advisory agency, the body that acts on maps. A parcel map is the simpler map used for small divisions; a tentative map is the first, proposed version of a map, and the final map is the surveyed version that is recorded. Table 9.1-1 shows that the Planning Commission decides tentative parcel maps and tentative subdivision maps after a public hearing, and that its decision may be appealed to the City Council.

Sources: Modesto Municipal Code Table 9.1-1, 4-4.404, 4-4.503, 4-4.506 and 4-4.507 and 4-4.601; City of Modesto Planning Division Fees and Land Development Fees, FY 2026-2027; Government Code 66411.7.

Section 4-4.502 sets the parcel map steps. Staff send the tentative parcel map to City departments and utilities, which have 15 days to reply; no reply means no objection. The Commission may approve the map "subject to the dedication of necessary right-of-way for streets and easements, the installation of all improvements along the frontages of the property so divided," and utilities to each lot, and "All lot sizes shall conform to the provisions of the zoning regulations." It may not approve a map if it finds the map is not consistent with the General Plan, or the site is not physically suitable for the project or its density.

After approval, Section 4-4.503 gives 24 months to file the parcel map, which a registered civil engineer or licensed land surveyor prepares. Section 4-4.504 then holds back every building permit on the new parcels until the map is recorded with the County Recorder. When a map divides an existing building, Section 4-4.505 requires the Chief Building Official to certify that each part will "meet current code standards for new construction." That rule matters for anyone planning to split an existing duplex onto two lots.

The City's map submittal requirements ask for eight copies of the Uniform Development Application, a financial interest disclosure form, evidence of ownership, and "Thirty (30) sets of the subdivision or parcel map." A lot line adjustment, which moves a line between two lots without making a new one, needs no map: under Section 4-4.506 the Secretary of the Planning Commission approves it if the lots still meet the zone's rules.

Design and Improvement Rules for New Lots

Section 4-4.302 sets design rules for every subdivision. Side lot lines should meet the street at right angles where practical. "The size and shape of each lot shall be in conformance to the zoning regulations." And "No land subject to flooding or deemed by the Planning Commission to be uninhabitable shall be plotted for residential occupancy." All new utility lines, including gas, water, sewer, power and cable, go underground. Where a street is less than 60 feet wide, a planting and utility easement 3 feet wide runs along each side.

Section 4-4.802 requires the subdivider to build streets and alleys, drainage, curbs and gutters, sidewalks, sewer and water mains to each lot, and street lights to the City's standard specifications. Section 4-4.803.1 adds street trees. Where the City makes a subdivider build lines larger than the subdivision needs, Section 4-4.802.1 provides for repayment of the extra cost, without interest. Section 4-4.901 lets the Planning Commission grant an exception to these rules for "exceptional or extraordinary circumstances," such as the shape of the land.

Two overlays add steps. Section 4-4.305 says a map that includes a designated landmark site "will be deemed complete only when proof of project approval by the Landmark Preservation Commission has been submitted." In a flood zone, Section 9-4.503 requires each map to show the flood areas, base flood elevations and the lowest floor of every proposed home. The flood zones and landmarks page covers both.

SB 9 Urban Lot Splits in Modesto

SB 9 lets an owner in a single-family zone split one lot into two under Government Code 66411.7. Modesto has not written its own rules for it. The City's adopted Housing Element says: "The City has not adopted an SB 9 ordinance or objective standards." Its Program A-15 promised a code amendment, an SB 9 webpage and streamlined review "By Q1, 2025," with a goal to "Increase SB 9 unit production to 10 annually." Supplement 72 of the code, current to May 2026, still has no SB 9 section.

So the state rules apply as written. Under Section 66411.7:

• The split makes no more than two parcels "of approximately equal lot area," and neither may be "smaller than 40 percent of the lot area of the original parcel."
• Each new parcel is at least 1,200 square feet. A city may set a smaller size by ordinance; Modesto has not, so 1,200 applies.
• The lot must be in a single-family zone, which in Modesto includes R-1. The split may not require demolition or alteration of housing "occupied by a tenant in the last three years," or of rent-restricted housing.
• The lot may not be a City landmark site, and the split may not demolish a contributing building in a historic district.
• The applicant signs an affidavit to live in one of the homes "as their principal residence for a minimum of three years."
• The City must approve or deny a complete application "within 60 days," or it is deemed approved.
• The City need not allow more than two homes on each new parcel, counting ADUs.

Two of Modesto's own map rules give way here. Section 4-4.502(c) lets the Commission require street dedication and frontage improvements on a parcel map, but Section 66411.7(b)(3) bars "dedications of rights-of-way or the construction of offsite improvements" for an urban lot split. And Table 9.1-1 sends tentative parcel maps to a Planning Commission hearing, while the statute requires approval "ministerially without discretionary review." The statute controls in both cases. A 5,000 square foot R-1 lot can be split into two lots of 2,500 square feet under SB 9, though neither would meet the 5,000 square foot R-1 minimum on its own.

SB 684 and SB 1123 Small-Lot Maps

SB 684 and SB 1123 created a fast map for small housing projects in Government Code 66499.41, and Modesto has no section of its own on them. The map must create "10 or fewer parcels," with "10 or fewer residential units." The lot must be either zoned for multifamily homes and "no larger than five acres," or vacant, zoned for single-family homes, and "no larger than one and one-half acres." New parcels must be at least 600 square feet, or 1,200 square feet where zoned for single-family use, and the homes must average no more than 1,750 net habitable square feet. The City must act within 60 days.

In Modesto, Table 3.1-1 permits multiple-family homes in R-2, R-3, MU-P and MU-H, so lots in those zones can use the multifamily route. The R-2 and R-3 minimum densities in Section 10-4.104 still apply to the homes built. The version of Section 66499.41 read for this page was amended by SB 1090, effective September 30, 2026, and becomes inoperative on January 1, 2027, when a newer version takes over.

Where to Go Next

Related on VanPlex: the Modesto overview, the SB 9 guide and the SB 684 and SB 1123 guide.

Frequently Asked Questions

Official sources (checked October 2026)