Concord | Lot size and subdivisions

Concord, California Lot Size and Subdivisions: Minimum Lots, Small Lot Subdivisions, Maps, SB 9 Lot Splits and Hillside Lots

Concord sets lot sizes in its Development Code (Title 18) and the steps for dividing land in its Subdivision Ordinance (Title 17), which the City replaced in full in 2017. A standard house lot is 6,000 to 12,000 square feet, but a chapter on small lots allows lots of 1,440 or 1,920 square feet with a Planning Commission permit. Neither title has a section on SB 9 lot splits, so the City works from a handout and state law. This page covers the lot standards, the small lot chapter, who decides each map, the SB 9 steps and the hillside rules. The Concord overview has the summary.

Minimum Lot Standards by District

Sources: Concord Development Code Tables 18.30.030, 18.30.040, 18.35.030(B), 18.40.030, 18.45.030 and 18.120.060(A).

• How width and depth are measured. The code defines lot depth as "the distance from the midpoint of the front property line of a lot to the midpoint of the rear property line," and lot width as the distance between the side lot lines "measured at a right angle to the lot depth at the midpoint of the lot depth line."
• Streets and easements are left out. Section 18.150.030 says rights-of-way, access easements "and any portion of a flag or corridor access lot" shall "Be excluded from the gross lot area and shall not be included in the minimum net lot area required for a site, allowable density, lot coverage, or floor area ratio."
• Individual units inside a project. Footnotes to the RM, RH, commercial and downtown tables say the lot standard "does not apply to small, independent parcels corresponding to individual dwellings within a larger multifamily residential, mixed-use, or townhome development."
• Lots split by a district line. Under Section 18.15.040, the lot area, width and frontage rules "of the district that covers the greatest portion of the lot area shall apply to the entire lot."
• Small changes. A minor exception can reduce lot size, lot width or lot depth by up to 10 percent. The Planning Division decides it, and the Zoning Administrator holds a hearing if someone asks for one.
• Old undersized lots. Section 18.530.050 says a nonconforming parcel "shall be considered a legal building site if it meets at least one of the following criteria." One of them is a parcel that "was legally created by a recorded deed before the effective date of the zoning amendment that made the parcel nonconforming."

Small Lot Subdivisions

Chapter 18.155 sets standards "for single-family detached and attached housing units on small lots (less than 6,000 square feet)." Its stated aims include to "Reduce the need for lengthy and cumbersome permitting procedures for small lot development." The chapter is "intended for use in the RS, RL, RM, CMX, and CO zoning districts" and is "principally intended for single-family homes, townhomes, patio homes, courtyard homes, duets, and similar single-family detached and attached housing types."

• The permit. Section 18.155.030: "Small lot, single-family detached and attached subdivisions shall first obtain a planned development use permit (PDUP)." The Planning Commission decides it at a public hearing.
• Smallest lot. Table 18.155.040(A) gives 1,920 square feet in RL and RS and 1,440 square feet in RM, CMX and CO, with a 24 foot width for a detached house and 18 feet for an attached one.
• The density cap still applies. In RL and RS, "the minimum lot size of 1,920 square feet can only be achieved if the average lot size is 4,356 square feet or higher, or if substantial areas within the subdivision are set aside as common open space." An acre is 43,560 square feet, so ten lots of 4,356 square feet fill one net acre.
• Coverage for the whole site. In RS and RL, "the sum total coverage of all proposed buildings and structures shall not exceed 40 percent of the gross land area of the subdivision."
• Next to house districts. Where a small lot project is in or next to an RS or RR district, side setbacks from those properties are eight feet, rear setbacks are 20 feet for lots of 3,000 to 5,999 square feet and 15 feet for smaller lots, and "A landscaped planter strip of at least five feet in width" with trees is required along the shared line.
• Other standards may be approved. The review authority may consider alternate standards if they would, among other things, "Result in a project which is more compatible with the surrounding neighborhood."

Source: Concord Development Code, Table 18.155.040(B). On lots of 3,000 square feet or more, one side setback may be reduced to zero if the two sides total 6, 8 or 10 feet by lot size. Lot depth for a detached house may drop to 60 feet where 15 percent of the site is one common open space.

Design Rules for Small Lots, Townhomes and Courtyard Homes

• Variety. Section 18.155.060: "In subdivisions with fewer than 20 lots, at least three unique front elevations and floor plans shall be provided," and four in larger ones. Blocks are to be "no longer than 600 linear feet."
• Three stories in RS. "For projects in the RS zone, no more than 25 percent of the units may be three stories tall."
• Garages. "Garage faces shall be recessed a minimum of five feet from the primary facade of the residence," and "On no residential unit shall the garage comprise more than 50 percent of the front building facade."
• Parking. "Two covered parking spaces shall be required for each housing unit," and "Two additional parking spaces for each unit shall be available for the use of residents and guests," which may be driveway, alley or street spaces.
• Open space. Each lot needs private open space of 60, 150 or 300 square feet by average lot size. Projects with an average lot under 4,356 square feet, or with 15 homes or more, also need common open space of 140 to 175 square feet per lot.
• Homeowners association. "A homeowners' association (HOA) shall be required to provide ongoing maintenance for private streets and utilities, alleys, private open space and recreational facilities," and other common areas.
• Second units. "Accessory dwelling units are permitted in small lot subdivisions."
• Townhomes. Section 18.155.070 defines a townhome as "a series of three or more adjacent one-family dwelling units, each on an independent parcel, which are connected by common walls along the side property lines." Street-facing walls need a projection or recess for every 25 feet, and "no more than two side by side units may be covered by one unarticulated roof."
• Courtyard homes. Section 18.155.080: "No more than six units shall be accessed from a single courtyard." The drive area must be at least 16 feet wide and 20 feet wide at the street, and "Courtyards shall not exceed 100 feet in length."

Who Decides a Map

A subdivision map is the recorded drawing that creates new lots. Section 17.05.140 describes two stages: "city approval of a tentative map or vesting tentative map and then city approval of a parcel map (for a subdivision that results in four or fewer parcels) or a final map (for a subdivision that results in five or more parcels)." The City calls four or fewer parcels a minor subdivision and five or more a major subdivision.

Sources: Concord Municipal Code Table 17.05-1, 17.10.030, 17.10.070, 17.25.130 to 17.25.190 and 17.35.030 and 17.35.040.

• Before filing. "The applicant shall meet with Department staff to review the application for completeness and accuracy prior to submittal."
• Completeness. "Within 30 calendar days of application filing, the Department shall inform the applicant in writing that the application is complete and has been accepted for processing, or that the application is incomplete."
• Hearing. Section 17.10.070: "The review authority shall take action on a tentative map or tentative parcel map application at a noticed public hearing." Mailed notice goes out at least 10 calendar days ahead, to owners and renters within 300 feet for a minor subdivision and 500 feet for a major one.
• Findings. The City must find, among seven findings, that the map is consistent with the general plan and the Development Code and that "The site is physically suitable for the proposed type and density of development."
• Life of the approval. "A tentative map or tentative parcel map approval expires after 24 months." An extension, which the City may grant or refuse, can run "up to a maximum of six years," and the request must be filed "at least 10 days before the expiration date."
• Vesting maps. A vesting tentative map keeps in force "the city's ordinances, policies, and standards in effect at the time the vesting tentative map application is deemed complete," for "two years after the recording of the final map or parcel map."
• Parcel map. "A parcel map may be approved in full by the City Engineer if it complies with the requirements of the Map Act, this chapter, the tentative parcel map, and all attached conditions of approval."
• Lot line adjustment. Moving a line between up to four existing lots with no new lot is decided by the City Engineer: "Within 30 calendar days of accepting an application as complete, the City Engineer shall approve, approve with conditions, or deny the application. No public notice or hearing is required."

Lot Design, Flag Lots and Condominiums

• Buildable. Section 17.20.030 requires the City to find each proposed parcel buildable, "with at least one building site that can accommodate a structure in compliance with the Development Code."
• Dimensions. Parcels "shall conform with minimum requirements of the applicable zoning district as specified in the Development Code, except that flag lots may be created."
• Frontage. "Residential parcels shall have frontage on, and take direct access from a public or private street or a shared open space such as a courtyard, plaza, or pedestrian walkway. An alley is not considered a street for the purpose of this requirement."
• Flag lots. A flag lot reaches the street by a narrow strip. "Use of flag lots shall be minimized and limited primarily to situations where use of a standard frontage configuration is undesirable due to unique site conditions," and "New flag lots shall not be created by a parcel map in developed areas where these lots are not in character with the surrounding neighborhood and the existing pattern of development."
• Design modifications. Section 17.20.070 lets the City change a design standard at map approval in five cases, one of which is that "The subdivision is located in an urban infill area with existing streets, utilities, or other public improvements that do not conform to the standards in this chapter."
• Condominiums. A condominium is one building or site sold as separately owned units. Section 17.35.030: "All condominium projects, regardless of the number of units created, require Planning Commission approval of a use permit." The lot dimension rules "shall not apply to condominiums, condominium conversions, and townhouses." Each condominium needs at least 200 cubic feet of lockable private storage.
• Converting apartments. A conversion of rental apartments to condominiums needs a use permit and a tenant relocation plan, and conversions in a year "may not exceed five percent of the total rental units in development of four or more units." The tenant rules are on the rent stabilization and tenant protections page.

SB 9 Urban Lot Splits

SB 9 is the 2021 state law that makes a city approve a split of one single-family lot into two, with no hearing. Government Code 66411.7 says a city "shall ministerially approve" a parcel map for an urban lot split that meets its tests. Ministerial approval means staff check the application against fixed rules. A search of the 58 saved files of Titles 17 and 18 found no section on urban lot splits. The City's SB 9 handout, last updated 4/28/26, says "The City of Concord is currently refining its SB 9 ordinance, and the following instructions are subject to change." The handout sets out these rules:

• Where. "SB 9 applies only to parcels zoned Residential Single-Family (RS) or Rural Residential (RR)."
• Size. "In total, no more than two parcels may be created. Each new parcel must be at least 1,200 square feet in area," and "One parcel must be at least 40 percent of the gross area of the original parcel."
• Homes. "Lot split projects can have a maximum of two units per parcel, including ADUs and JADUs. This results in total of four units across both parcels."
• Owner. The owner signs an affidavit that they intend to live in one of the homes "for a minimum of three years from approval of the urban lot split." The handout adds that for this reason "at least one legal, habitable dwelling unit must exist on the site prior to approval of the urban lot split," and that limited liability companies "are therefore not eligible applicants for SB 9 urban lot splits."
• Deed restriction. The owner records a restriction "prohibiting any further subdivision under SB9 and any non-residential use of the property."
• Access. "The new parcels must have access to or adjoin a public right-of-way," and "An access drive or access easement shall be a minimum of 16 feet wide."
• Existing buildings. "Existing structures that would cross any proposed lot lines must be demolished prior to approval of the urban lot split."
• Empty parcel allowed. "A subdivision can occur without proposing any residential units on the new parcel."
• Three steps. First a lot split application to the Planning Division: "This step has a $2,000 deposit. (approximately 3-4 months)." Then "apply to Engineering to formalize the new map," which the handout puts at two to three months. Then a building permit for any new home.
• Notice and appeal. "SB 9 requires a ministerial process which occurs at staff level and without any public notification or public hearings." A decision "may be appealed pursuant to CDC 18.510.010(A)(1) within ten calendar days of the date of the decision."
• Private restrictions. "SB 9 does not override private Codes, Covenants and Restrictions (CC&Rs)."

The Housing Element Programs Document sets a date for the ordinance. Objective 9.2 reads "Adopt an ordinance to implement the provisions of SB 9 to establish ministerial review procedures for proposed lot splits of existing single-family residential lots by July 2026," and Objective 9.3 commits to an ordinance "allowing ADUs and JADUs to be constructed in addition to the two conventional dwelling units per lot provided for by SB 9." The code's Ordinance List, which runs through Ordinance 26-2 of September 8, 2026, shows no SB 9 ordinance. Ask the Planning Division whether one has been adopted since.

SB 684 and SB 1123 Small-Lot Maps

SB 684 and SB 1123 are state laws that require a city to approve small subdivisions for housing with no hearing. Government Code 66499.41 says a city "shall ministerially consider, without discretionary review or a hearing, a parcel map or a tentative and final map for a housing development project" where "The proposed subdivision will result in 10 or fewer parcels and the housing development project on the lot proposed to be subdivided will contain 10 or fewer residential units." The lot must be zoned for multifamily use and "no larger than five acres," or be "A vacant lot zoned for single-family residential development" that "is no larger than one and one-half acres." New parcels are "no smaller than 600 square feet," or 1,200 square feet on single-family zoned land, and the City must act "within 60 days."

Concord has no section on this statute. For a builder with an RM or RH lot, the statute and Chapter 18.155 are two separate ways to reach small lots. The City's small lot chapter starts at 1,440 square feet and needs a Planning Commission hearing. The statute starts at 600 square feet and has no hearing, but it has its own tests on density, tenants and unit size, including an average of no more than 1,750 net habitable square feet per home. Section 17.05.060 settles which rule governs where they collide: "In the event of any conflict between this title and the Map Act, the Map Act shall govern unless local divergence is permitted."

Hillside Lots

Chapter 18.300 applies "to any subdivision, new use, or structure (including accessory structures), additions to existing structures that exceed 50 percent of the size of the existing structure, and other development on any parcel with an average slope of 15 percent or greater." Slope is the vertical rise divided by the horizontal run.

• Density. "The maximum residential density for any hillside parcel shall be calculated according to" a figure in Section 18.300.030. The figure is an image and its values were not read. The review authority may reduce density further to protect safety, water quality or public views.
• Exemption. A parcel may be exempted from the density reduction when its average slope is under 20 percent, it was developed before or is "abutted on all four sides with developed properties," no open space adjoins it, and it "is less than five acres in size."
• Slope limits. "Land with an average slope of 30 percent or more shall not be developed. Development on land with an average slope of 20 percent or more shall be limited to a single-family dwelling."
• Existing lots. "Nothing in this chapter shall prohibit the construction and occupancy of a single-family residence on a hillside parcel created pursuant to the Subdivision Map Act and the city's subdivision ordinance."
• Ridgelines. "The highest point of any structure shall not be located within 100 vertical feet of a ridgeline."
• Paving. "For slopes up to 15 percent, impervious surfaces shall not exceed 40 percent of the gross land area." Impervious surfaces are roofs and paving that water cannot pass through.
• Building form. The tallest vertical wall plane may not exceed 20 feet from grade, with the building "stepping back a minimum of 10 feet at the 20-foot limit." Retaining walls "shall be limited to four feet in height, unless otherwise approved."
• Fences. "Chain link fencing, solid wood, masonry, or other opaque fence/wall materials are prohibited."
• New lots. New hillside lots must "avoid grading or building within 25 vertical feet of the top five-foot contour of a ridgeline or knoll."
• The permit. Section 18.445.040 calls "a new single-family residence on an existing parcel," a large addition or "a minor subdivision" a minor hillside development use permit, decided by the Zoning Administrator at a public hearing. "A major HDP is any residential subdivision, multifamily dwelling, or nonresidential structure on a hillside parcel," decided by the Planning Commission. A soils or geotechnical report is part of each application.
• ADUs. The living area of an accessory dwelling unit on a hillside lot is exempt from the hillside permit under Section 18.200.180.

Map Fees From July 1, 2026

Source: City of Concord, Fees and Charges for Various Municipal Services, Resolution No. 26-6042.1, Section D, items 26, 33 and 34. Deposits are drawn down at staff hourly rates.

Park land dedication or a fee in its place is also a condition of a parcel map or final map on residential land, and the sewer and street charges apply when homes are built. Those amounts are on the permits and fees page.

Where the Code, City Documents and State Law Differ

• Hearing on a lot split. Section 17.10.070 holds a noticed public hearing on every tentative parcel map. Government Code 66411.7 requires ministerial approval of an urban lot split, and the City handout says there is no public hearing. State law controls for a map that qualifies.
• Time. The handout estimates "approximately 3-4 months" for the Planning step of a lot split. The statute says an application "shall be considered and approved or denied within 60 days from the date the local agency receives a completed application," and that after 60 days with no decision "the application shall be deemed approved."
• Deposit. The handout, updated in April 2026, names a $2,000 deposit. The fee schedule effective July 1, 2026 lists a $2,500 deposit for an SB 9 preliminary application and a $5,000 deposit for SB9 parcel map review. Ask which applies to your filing.
• Affidavit on projects with no split. The handout's checklist says of the owner occupancy affidavit, "This is required for all SB 9 projects." Government Code 66411.7 requires the affidavit from "an applicant for an urban lot split." Government Code 65852.21, which covers two homes on one lot with no split, contains no affidavit.
• RM density. The small lot chapter is tied to district densities, and the code prints RM as both 33 and 32 homes per net acre. See the zoning districts page.

Limits of This Page

The code text is the publisher's copy, current through Ordinance 26-2 of September 8, 2026. The City's agenda system did not answer on October 10, 2026, so City Council and Planning Commission agendas were not read, and this page cannot say whether an SB 9 ordinance is scheduled. The density figure in Section 18.300.030, the figures in Chapter 18.155, the City's standard plans for streets, the application checklists other than the minor subdivision and SB 9 checklists, and the SB 9 deed restriction and affidavit forms were not read. Fees of the Contra Costa County Recorder and of outside agencies are not given.

Where to Go Next

Related on VanPlex: the Concord overview, the California SB 9 page and the SB 684 and SB 1123 page.

Frequently Asked Questions

Official sources (checked October 2026)