SB 9 Lot Splits, Duplexes and ADUs in Alhambra

Alhambra's single-family neighborhoods sit on lots that are often larger than the house needs. State law now lets many of those lots hold more homes: a second primary unit or a lot split under SB 9, and accessory dwelling units (ADUs) under state ADU law. For a buyer or investor, that changes what a lot may be worth. It does not mean every lot qualifies.

This page explains the rules, what Alhambra has adopted, and how to check a specific parcel. It is a summary, not legal advice, and the city's Planning Division makes the final call.

What does SB 9 allow?

SB 9 (Chapter 162, Statutes of 2021) is codified in Government Code 65852.21 (two-unit developments) and Government Code 66411.7 (urban lot splits). On a qualifying lot zoned single-family in an urbanized area, it gives an owner two by-right options, which can be combined, according to the HCD fact sheet on duplexes and lot splits:

• Two-unit development. Build up to two primary homes on the lot, plus ADUs as permitted under ADU law.
• Urban lot split. Divide the lot into two lots of roughly equal size, then build up to two units on each new lot.

The city must approve or deny a complete application within 60 days, and the review is ministerial: no public hearing and no discretionary design review. A city may still apply objective standards, but they cannot prevent two units of at least 800 square feet each, or prevent two 1,200-square-foot lots. A city can deny only if its building official finds, in writing, a specific adverse impact on public health and safety that can't be mitigated.

Other limits a city may impose under the statute:

• Setbacks of up to four feet from side and rear lot lines. None for an existing structure, or one rebuilt in the same footprint.
• Parking of up to one space per unit. None if the lot is within a half-mile walk of a high-quality transit corridor or major transit stop, or within one block of a car-share vehicle.
• Rentals of SB 9 units must be for terms longer than 30 days. No short-term rentals.

Which lots can't use SB 9?

SB 9 does not apply where the project would demolish or alter housing that:

• is rent-restricted by covenant for moderate-, low- or very-low-income households;
• is subject to any form of rent or price control; or
• has been occupied by a tenant in the last three years.

It also excludes parcels where units were withdrawn from the rental market under the Ellis Act in the last 15 years, and contributing structures in historic districts or properties listed as historic resources at the state or local level.

Environmental site conditions also disqualify a lot. SB 9 borrows the list in Government Code 65913.4(a)(6)(B)–(K), and the HCD SB 9 fact sheet gives examples: farmland, wetlands, fire hazard areas, earthquake hazard areas, flood risk areas, conservation areas, wildlife habitat and conservation easements.

For lot splits only, two more rules apply: a lot created by an SB 9 split can't be split again, and an owner can't split a lot next to one they, or someone acting with them, already split.

The tenant rule is the one that trips up investors most. A house that has been rented out in the last three years generally can't be demolished or altered under SB 9. A buyer planning an SB 9 project on a tenant-occupied rental is usually planning around a three-year wait.

Do you have to live on the property?

For a lot split, yes. The applicant must sign an affidavit stating they intend to live in one of the units as their principal residence for at least three years from approval. Community land trusts and qualified nonprofits are exempt.

For a two-unit development without a split, no. HCD has told cities that SB 9 does not allow an owner-occupancy requirement on two-unit developments. Its September 2024 letter to Laguna Beach is one example, summarized in the HCD fact sheet.

That difference shapes strategy. An investor who will not live on the property is generally limited to the two-unit path, plus ADUs. An owner-occupant can use either path.

How does Alhambra handle SB 9?

Alhambra's single-family zone is RL (Residential Low). In April 2025 the City Council adopted Ordinance O2M25-4844, an update to the zoning code. Its residential land-use table makes a multi-unit dwelling of no more than two units that meets Government Code 65852.21 a permitted use in the RL zone. In other words, an SB 9 two-unit project is allowed by right in RL.

The city has also been working on a fuller local SB 9 ordinance. Its 2024 Housing Element Annual Progress Report says the city was drafting urban dwelling and urban lot split standards and expected to take them to the City Council in 2025. The same report notes two SB 9 applications received in 2024, with one project reaching a certificate of occupancy. Whether those standards have since been adopted isn't stated on the city's website. Ask the Planning Division which objective standards apply today before you design anything.

Is there an SB 9 property eligibility map for Alhambra?

As of October 2026, the City of Alhambra's website does not offer a parcel-level SB 9 eligibility lookup. Without one, eligibility is a checklist:

1. Zoning. Find the parcel on the city's zoning map. SB 9 applies in the single-family RL zone. Lots in multi-family zones aren't SB 9 lots, though they may allow more units under their own zoning.
2. Jurisdiction. Confirm the parcel is inside the City of Alhambra. A mailing address isn't proof.
3. Tenancy. Has anyone rented the house in the last three years?
4. Historic status. Is the house a listed historic resource or a contributing structure in a historic district?
5. Hazard and environmental overlays. Fire, fault, flood and the other 65913.4 categories.
6. Lot size and shape. Can the lot split into two parcels of at least 1,200 square feet, neither smaller than 40% of the original, with access to a public right-of-way?

Then take the parcel number to the Planning Division at 111 South First Street, (626) 570-5034 or planning@alhambraca.gov.

How big are Alhambra lots?

Lot size decides whether a split is even arithmetically possible. Each new lot must be at least 1,200 square feet, and neither can be smaller than 40% of the original, so the original lot must be at least 2,400 square feet. Kelvin looked at the lot sizes recorded for Alhambra houses sold between October 2025 and September 2026:

Lot size (sq ft)	Houses sold	Share	Median price
Under 4,000	8	6%	$706K
4,000–4,999	18	13%	$895K
5,000–5,999	19	14%	$996K
6,000–7,499	45	33%	$1.05M
7,500–9,999	40	29%	$1.16M
10,000 and up	8	6%	$1.36M
All	138	100%

The median lot was about 6,700 square feet. The middle half ran from about 5,400 to 7,800 square feet. The smallest and largest groups have only eight sales each, so treat their medians as rough.

Threshold	Houses sold at or above it	Share of 138
2,400 sq ft (SB 9 split minimum)	137	99%
5,000 sq ft	112	81%
6,000 sq ft	93	67%
7,500 sq ft	48	35%
10,000 sq ft	8	6%

Kelvin's take: nearly every Alhambra house lot clears the SB 9 minimum on paper, so lot size alone says little about whether a lot works. What makes a lot workable is its width and depth, where the existing house sits on it, and whether a second lot can reach the street. Then come the rules above on tenants, historic status and hazards. A 7,500-square-foot lot with the house centered on it can be harder to split than a 6,000-square-foot lot with a deep, open back yard.

What can you build with an ADU instead?

For many Alhambra owners, an ADU is the simpler route. It needs no lot split, no owner-occupancy affidavit, and no three-year tenant look-back. State ADU law is summarized in the HCD ADU Handbook (March 2026) and the HCD ADU fact sheet:

• On a single-family lot, cities must allow at least one ADU converted from existing space, one junior ADU (JADU), and one new detached ADU of up to 800 square feet with four-foot side and rear setbacks.
• JADUs are built inside the house, including an attached garage, and are capped at 500 square feet. If a JADU shares a bathroom with the main house, the owner must live in one of the two.
• No owner-occupancy requirement applies to ADUs themselves.
• No impact fees on ADUs under 750 square feet or on JADUs.
• Size caps in a local ordinance can't be set below 850 square feet, or 1,000 square feet for an ADU with more than one bedroom.

Alhambra's ADU informational handout (March 2026) sets out how the city applies this:

Alhambra ADU standard	Lots with a single-unit home
Number allowed	1 detached or attached ADU, plus 1 conversion ADU, plus 1 JADU
Detached ADU size	Up to 1,200 sq ft (over 800 sq ft must meet the zone's floor-area or lot-coverage limits)
Setbacks	4 ft side and rear for new construction
Height	2 stories, 25 ft maximum
Parking	1 space per ADU; none within a half-mile walk of public transit; none for JADUs
Estimated city permit fees	About $13,200 for an 850 sq ft ADU; about $16,000 for 1,200 sq ft, before mechanical, electrical and plumbing permits

How many units can one Alhambra lot hold?

Per HCD, a lot that is not split can have up to two primary homes under SB 9 plus ADUs as permitted under ADU law, for example two SB 9 units, an ADU and a JADU. Where a lot is split under SB 9, the city has to allow two units on each new lot, and ADUs and JADUs count toward those two. The four-unit outcome from a split is real but needs an owner-occupant applicant and a lot that clears every exclusion.

What does this mean for a buyer's valuation?

Extra units have value only if they can be built at a cost and timeline that make sense. A few rules of thumb Kelvin uses when a seller prices in "SB 9 potential" or "ADU potential":

• Price the house as it is first. Use the closed sales of comparable houses. Treat development potential as an option, not as finished square footage.
• Check the exclusions before the numbers. A rental with tenants in the last three years, a historic designation or a hazard overlay can take SB 9 off the table entirely.
• Count the full cost. Design, permits, utility connections, construction and time. The city's fee estimates above cover only part of the permit cost.
• Match the path to the buyer. An investor who won't live on site is usually limited to the two-unit path and ADUs. A lot split needs an owner-occupant.
• Older houses cut both ways. The median Alhambra house sold in the period was built in 1936, and 116 of 139 were built before 1950. That can mean a garage worth converting, or a house with historic status that limits what can change.

Done well, an ADU or second unit can add rental income or space for family on a lot the buyer was going to own anyway. Done on a lot that doesn't qualify, it is a design fee and a lesson.

Frequently asked questions

Can I split my lot in Alhambra under SB 9?

Possibly, if the lot is zoned RL, sits in the City of Alhambra, can produce two lots of at least 1,200 square feet each with neither under 40% of the original, hasn't had a tenant in the last three years, and isn't excluded for historic or environmental reasons. You must also sign an affidavit that you intend to live in one unit for three years. Confirm with the Planning Division.

Does Alhambra allow SB 9 duplexes?

Yes. Alhambra's zoning code, as amended in April 2025, lists a development of no more than two units that meets Government Code 65852.21 as a permitted use in the RL zone.

How many ADUs can I build on a single-family lot in Alhambra?

Under the city's March 2026 handout, one detached or attached ADU, one conversion ADU, and one JADU, subject to the city's standards.

Do I need to live on the property to build an ADU?

Not for an ADU. A JADU that shares a bathroom with the main house requires the owner to live in either the JADU or the main house.

Does SB 9 apply to a house I rent out?

Generally not, if building would mean demolishing or altering housing that has had a tenant in the last three years.

Where can I check if my Alhambra property is eligible for SB 9?

As of October 2026 the city does not publish an SB 9 eligibility map. Check the zoning map, then contact the Planning Division at (626) 570-5034 or planning@alhambraca.gov with the parcel number.

Sources

• California Government Code § 65852.21 (two-unit developments)
• California Government Code § 66411.7 (urban lot splits)
• HCD Housing Law Fact Sheet: Duplexes and Lot Splits (SB 9), April 2026
• HCD SB 9 Fact Sheet
• HCD Accessory Dwelling Unit Handbook, March 2026
• HCD Housing Law Fact Sheet: Accessory Dwelling Units, April 2026
• City of Alhambra: Ordinance O2M25-4844 (zoning code amendments)
• City of Alhambra: 2024 Housing Element Annual Progress Report
• City of Alhambra: ADU Informational Handout
• City of Alhambra: Accessory Dwelling Units
• City of Alhambra: Zoning Map
• Lot-size figures: Kelvin Huang's analysis of closed single-family sales in Alhambra, October 2025 – September 2026