Multifamily ADU Construction Around Westlake Village

Multifamily ADU Rules After SB 1211

SB 1211, which took effect in 2025, widened what apartment and condo lots can add. Where a multifamily building already stands, the owner may build as many as eight detached ADUs, provided the new units never outnumber the existing ones. So a fourplex tops out at four detached ADUs, while a twelve-unit building reaches the cap of eight.

Conversions come on top of that. Rooms nobody lives in, including storage rooms, boiler rooms, passageways, attics, basements and garages, can become ADUs. At least one such conversion must be permitted, and the allowance runs to a quarter of the building's unit count. On a lot where the multifamily building is only proposed, two detached ADUs are allowed.

• Up to eight detached ADUs, capped at the existing unit count
• Conversions of storage, garage and other non-livable space
• At least one conversion, up to 25 percent of existing units
• Up to two detached ADUs with a proposed multifamily building

Multifamily Properties Around Westlake Village

Westlake is mostly single-family, but it also has townhome and condominium communities, smaller apartment buildings and mixed properties on both sides of the county line. Many of these were built in the same planned-community era as the surrounding tracts, with carport rows, detached garage buildings and wide landscaped setbacks. Those features are exactly where ADUs tend to fit.

A carport row can sometimes be enclosed and converted. A detached garage building may hold a unit at one end. Surplus parking areas or wide side setbacks along a property line can take a small detached unit. Each of these options depends on the site plan, fire access, existing utilities and, inside the City of Westlake Village, what the City's planning staff confirms during Zoning Clearance.

ADUs on Condominium Properties and HOA Approval

Condominium and townhome complexes add a governance question. In most condo projects, the land and the buildings outside each unit's walls are common area owned by the association. An ADU on that land is an association project, not something one owner can build alone. The board, and often a vote of the members, has to approve it, and the governing documents may need to be amended.

We can help an association understand what the property could hold and what the design and permit process looks like, so the board has something concrete to discuss. Selling an ADU separately as a condominium is a different matter. State law allows it only in a city or county that has passed its own ordinance allowing it, and we confirm whether that applies before anyone plans around it.

Permits and Site Work for Multifamily ADUs in Westlake

On the Los Angeles County side, a multifamily ADU in the City of Westlake Village goes through the City's Zoning Clearance and then LA County Building and Safety plan check. Parcels across the county line go to the City of Thousand Oaks instead. Fire department review carries more weight on multifamily sites because access lanes, hydrant distances and sprinkler requirements can all come into play.

Utilities are usually the controlling cost. A property with several new units may need a larger electrical service from Southern California Edison, new meters, a larger water service and an evaluation of the existing sewer lateral's capacity. Water for City of Westlake Village properties comes from the Las Virgenes Municipal Water District, and connection requirements are set by the provider. We map all of that before finalizing how many units to build.

Phasing Multifamily ADU Construction With Tenants in Place

Most multifamily owners need to keep the existing units occupied while ADUs are added. That shapes the schedule. Utility shutoffs are planned and announced, staging is placed away from entries and parking, and noisy work stays within permitted hours. Converting one storage room or carport at a time, rather than all at once, can reduce disruption and spread the cost.

We work out a phasing plan with the owner or board before construction, so residents know which areas will be closed and when.