Multifamily ADU Construction in Santa Clarita

Multifamily ADU Rules in California

SB 1211 took effect in 2025 and raised the ceiling: a parcel that already has an apartment building may now gain as many as eight freestanding ADUs, capped at the count of existing apartments. A fourplex, for example, could add up to four detached units. A lot where a multifamily building is only proposed can add up to two detached ADUs.

On top of detached units, owners can convert non-livable space inside existing buildings, such as storage rooms, laundry rooms, boiler rooms or garages, into ADUs. Every qualifying building gets at least one of these, and larger ones can convert space for 25 percent of their unit total. A twelve-unit building, for instance, could convert space for up to three. Those detached and converted counts stack, which is why multifamily properties are some of the strongest ADU candidates in the valley.

How Santa Clarita Reviews Multifamily ADUs

The city's ADU handout for single-family homes says that ADUs on multifamily properties have different development standards and should be discussed with the Planning Division directly. In practice that means we start every multifamily project with a review of the zoning, the existing site plan and the city's current multifamily ADU standards before any design.

Review is still ministerial under state law. The Planning Division looks at the ADU standards first, and Building & Safety handles plan check after. If the property sits outside city limits, in Castaic or Val Verde for example, LA County's Regional Planning and Public Works handle the same steps.

Finding ADU Space on Apartment Lots

Many older apartment properties in Newhall and Canyon Country have carports, detached garages, storage buildings or surface parking along an alley. Each is a possible ADU site. Carports can sometimes be enclosed and converted. Parking lots may have room for detached units at the back. Parking is a real concern on multifamily sites because tenants depend on it. State law caps ADU parking requirements and says lost garage or carport parking need not be replaced when that space becomes an ADU. That does not erase tenant expectations or lease terms, so we help owners plan where cars go before units are drawn.

Fire department access is the other constraint. Larger sites need fire lanes and hose reach to every new unit, and LA County Fire, which serves the city under contract, reviews those layouts. A detached ADU tucked behind a carport at the far end of a long lot may need a wider path, a closer hydrant or sprinklers to satisfy access requirements, so we check the distances before choosing locations.

• Underused carports and detached garages
• Storage, laundry and mechanical rooms
• Rear parking areas with room for detached units
• Unused yard space between buildings

Utilities and Construction on Occupied Properties

Adding several units to an existing apartment property puts new demand on the water service, sewer main and electrical service. A building with one master meter may need a service upgrade with Southern California Edison, and the water meter size may need review with SCV Water. These are often the longest-lead items on a multifamily ADU project.

Construction happens with tenants living on site. We phase work so walkways, parking and trash enclosures stay usable, schedule shutoffs with notice, and keep the work area fenced. Clear communication with the property manager keeps complaints down. Written notices before noisy work, posted schedules and a single point of contact for tenant questions go a long way on a property where people work from home.

Selling Multifamily ADUs Separately

State law, under AB 1033, lets ADUs be sold separately as condominiums only where the city or county has adopted a local ordinance permitting it. Santa Clarita's current ADU guidance says ADUs may not be sold or conveyed separately from the main residence, so for now plan on holding new units as rentals.

Rental terms must be longer than 30 days, and the units cannot serve as short-term rentals. For income property owners, that usually fits the business plan anyway. Studios and one-bedrooms with their own entries tend to rent to long-term tenants, and keeping them as part of one parcel simplifies financing, insurance and property management.