A subdivision site plan is a different document from a standard residential or commercial permit site plan. Most homeowners will never need one. Developers, builders, and property owners splitting or combining lots absolutely will.
I’m Engineer Wasim of Site Plans Online USA. This guide explains what subdivision site plans are, when they’re required, and what the documents must show.
What Is a Subdivision?
A subdivision is the process of dividing one or more parcels of land into smaller parcels, each with its own legal description and assessor parcel number.
There are several types of subdivision approvals depending on the number of lots and local jurisdiction:
Minor subdivision (lot split): Typically 2–4 lots. Usually processed administratively without a public hearing. California’s SB 9 allows qualifying single-family lots to be split into two without a public hearing.
Major subdivision (tract map): 5 or more lots. Requires a tentative tract map, public hearing, Commercial Site Planning Commission Review approval, environmental review, and eventually a final map recorded with the county. Some complex divisions may also look into a Conditional Use Permit Guide to see if additional land use approvals are required.
Parcel map: Generally 2–4 lots in California. Processed through the county surveyor or engineer.
What a Subdivision Site Plan Must Show
Subdivision documents are more complex than standard Permit Site Plans and typically involve multiple sheets:
Sheet 1 — Title Sheet:
- Project title and location
- Legal description of the parent parcel
- Name and contact info of subdivider and engineer of record
- Index map showing project location
- General notes and conditions
Sheet 2 — Existing Conditions / Topographic Plan:
- Existing parcel boundaries with bearings and distances
- Existing easements and utilities
- Topographic contours at 1-foot or 2-foot intervals
- Existing structures (if any)
- Adjacent parcel information
Sheet 3 — Tentative/Proposed Subdivision Map:
- Proposed lot lines with dimensions and areas
- Proposed parcel numbers
- Proposed public and private streets, alleys, and easements
- Building setback lines for each proposed lot
- Lot coverage and density calculations
- Proposed utility connections
Sheet 4 — Grading and Drainage Plan:
- Proposed finished grades
- Drainage flow direction arrows
- Storm drainage infrastructure
- Cut and fill calculations
- PE Stamp Services required
Sheet 5 — Street and Infrastructure Plans (larger subdivisions):
- Street cross-sections and profiles
- Curb, gutter, and sidewalk layout
- Utility plan (water, sewer, dry utilities)
- PE stamp required on all engineering sheets
Who Prepares Subdivision Documents
Subdivision maps involving the establishment of legal boundaries must be prepared by a licensed land surveyor (for boundary survey elements) and a licensed civil engineer (for grading, drainage, and infrastructure design).
The overall site plan for a subdivision development, showing lot layouts, setbacks, and land use, can be prepared by a civil engineer or a professional land use planner, depending on the application type.
We prepare subdivision concept site plans for planning applications. For recorded subdivision maps, you’ll need a licensed surveyor and civil engineer. Contact us to discuss your specific project.
SB 9 Lot Splits in California
California Senate Bill 9 (effective January 1, 2022) allows most single-family residential lots in urban areas to be split into two parcels without a hearing, subject to standards including:
- Each resulting parcel must be at least 1,200 sq ft
- The lot must not be in a historic district, fire hazard zone, earthquake fault zone, or flood zone
- The applicant must submit a parcel map application
For SB 9 lot split applications, we prepare the site plan showing the existing and proposed parcel configuration. See also: ADU Site Plan Guide — SB 9 is often used in conjunction with ADU development.
Whether you need to clear up municipal requirements or are ready to move forward, you can click here to Discuss Your Subdivision Project with our team, or check out our Cost Calculator to estimate your upfront planning layout expenses.
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