The short answer is, “Yes!” You can build more than one accessory unit (ADU) on your property in Rosemead, California, but the specific number depends on whether your lot is zoned for a
single-family home or a
multifamily residence (like an apartment or duplex).
Because California state laws have been evolving rapidly as we enter into 2026, Rosemead must follow "ministerial" approval processes, meaning if you meet the state requirements, the city of Rosemead (and anywhere else in California) must grant the permit.
1. If you have a Single-Family Home
On a standard residential lot, you are generally allowed to have up to
two accessory units in total:
- One Full ADU: This can be detached (a standalone cottage) or attached to your main house.
- One Junior ADU (JADU): This must be contained within the walls of your existing house (like a bedroom conversion) and is limited to 500 square feet. It must include an efficiency kitchen.
2. If you have a Multifamily Property
If your lot already has a duplex or an apartment building, the rules are even more generous:
- Detached ADUs: Under SB 1211 (effective 2025/2026), you can build up to
eight detached ADUs on the lot, provided the total number of ADUs does not exceed the number of existing primary units on the property.1
- Converted ADUs: You can also convert non-habitable spaces (like storage rooms, garages, boiler rooms, or attics) within the existing building into ADUs. You are allowed at least one, or up to
25% of the existing unit count.
Key Rules to Keep in Mind
The maximum size is 1,200 sq. ft. for a detached ADU with 2+ bedrooms, and 800–850 sq. ft. for 1 bedroom or studio.
The setback minimum is 4 feet from side and rear property lines. No parking is required for the ADU if you are within 1/2 mile of public transit (which covers a lot of Rosemead). The height limit is usually 16–18 feet for detached units. But the limit can go up to 25 feet if the unit is near public transit in some cases.
A Note on SB 9 (Lot Splits)
If you are seeking to do more than just add "accessory" units, Rosemead also allows
SB 9 Urban Lot Splits. This allows you to split a single-family lot into two and build up to two units on each (a total of 4 units). However, if you use SB 9 to split the lot, you generally cannot add additional ADUs beyond those four units.
Reach out to us at
SGV ADU Construction Contractors for more information on this or other ADU questions in Rosemead and all of the San Gabriel Valley. Our phone number is
626-900-0952 (click to call).
