Can I split my lot under SB 9?

What SB 9 does

SB 9 requires a city to approve ministerially — without discretionary review or a hearing — a housing development of up to two units on a lot in a single-family residential zone, where the statutory conditions are met. Separately, it requires ministerial approval of a parcel map for an urban lot split, producing two roughly equal parcels each at least 1,200 square feet (Gov. Code §66411.7).

Stack the two and a single-family lot can in principle become two parcels carrying up to four units. That is the headline, and it is why the law has been litigated ever since it passed.

Where the litigation actually stands

1. 2021 — SB 9 passes

   Its stated purpose is framed around ensuring access to affordable housing.

2. April 2024 — a trial court exempts five charter cities

   In City of Redondo Beach v. Bonta, a Los Angeles Superior Court judge held SB 9 unconstitutional as applied to charter cities, reasoning that it was not reasonably related and narrowly tailored to its stated purpose. Charter cities have constitutional authority over municipal affairs, so a state law reaching into local land use has to clear that bar. The ruling bound only the cities in that case.

3. 1 January 2025 — SB 450 takes effect

   The Legislature expanded SB 9's stated purpose to include housing supply, not only affordability, and addressed application to charter cities. This was a direct response to the flaw the trial court had identified.

4. 2025 — general law cities lose their challenge

   In City of Rancho Palos Verdes v. State, the Court of Appeal affirmed that general law cities are not protected by the municipal affairs doctrine and must yield to conflicting state law. That question is settled.

5. 12 November 2025 — the charter city ruling is vacated

   The Second District Court of Appeal agreed that SB 450 is an intervening change in law entitled to consideration, vacated the 2024 judgment, and sent the case back to the trial court. The decision was unpublished, and the appellate court did not decide whether SB 9 is constitutional as applied to charter cities. That question is now back before the trial court.

Who to ask, and what we will not tell you

We are a licensed General B contractor. We can tell you what a structure costs to build, what your site will take, and where the money goes. We are not lawyers, and whether SB 9 applies to your specific parcel in your specific city today is a legal and planning question rather than a construction one.

So: take the eligibility question to your city's planning counter, and if you are about to commit real money to a lot split, take it to a land use attorney. That is a few hundred dollars against a project worth several hundred thousand, and it is the cheapest line in the whole budget.

The part that is not in dispute: permission was never the expensive problem

Here is what gets lost in five years of litigation coverage. Very few SB 9 projects have actually been built, and the reason is not that cities blocked them all. It is that building two or four new homes on a lot that currently holds one is a genuinely large construction project, and the arithmetic is not softened by having a right to do it.

Ground-up new construction in our area runs From $500/sq ft. On top of that a lot split brings its own costs that a single-lot build does not: survey and the parcel map itself, separate utility services to each new parcel, driveway and access requirements, drainage, and frequently a service upgrade. None of those scale down because the units are small.

• Utilities are the item that most often kills the pencil. Two parcels generally means two services. Trenching, connections and capacity charges are real money and they are invisible on a pro forma built from a per-square-foot figure.
• Access and drainage. Getting a compliant driveway and legal drainage to a rear parcel is frequently the constraint that decides whether the split is buildable rather than merely permittable.
• Setbacks and the buildable rectangle. Two parcels each at least 1,200 sq ft is a minimum lot size, not a guarantee that a house fits on it after setbacks.
• The lot split route carries an owner-occupancy commitment. Confirm the current requirement and its term with your city before you plan around selling either parcel.
• Financing two units at once. This is a development project rather than a home improvement, and it is underwritten differently.

Our honest view, as the people who would have to build it: treat SB 9 as a real tool with real friction rather than as found money. If your lot is a genuine candidate, the way to find out is to price the sitework and the utilities first, before spending anything on entitlement. That order is the opposite of how most people approach it, and it is the order that stops you paying for a parcel map on a project that was never going to pencil.

Common questions

Where to go next

Written by the team at Elusive Construction, a licensed California general contractor (B #1112902) building in Santa Clara and San Mateo counties. General information about how residential construction works — not legal advice. For your specific contract, talk to an attorney.