Multifamily ADU Construction in Malibu

Multifamily ADU Options Under California Law

SB 1211 widened the state rules for multifamily lots starting in 2025. Where an apartment building or duplex already stands, the owner may add as many as eight detached ADUs, capped so they never outnumber the existing homes on the lot. A duplex could therefore add two detached units, and a six-unit building up to six.

Owners can also turn spaces nobody lives in, like a storage room, a shared laundry, an old boiler room or a carport bay, into ADUs. The minimum is one such conversion, and the maximum is 25% of the units already on the property. Where the multifamily building is still on the drawing board, the project may include two detached ADUs alongside it.

Where Multifamily ADUs Fit in Malibu

Multifamily properties in Malibu cluster in a few places: along stretches of Pacific Coast Highway, around the Civic Center and on some beachfront parcels zoned for more than one unit. Many are older two- to eight-unit buildings with carports, storage rooms or laundry rooms that see little use. Those spaces are often the simplest ADU opportunity, because conversion adds no new footprint.

Detached units are harder on these lots. Older apartment buildings tend to cover much of the parcel, and what open land remains may be needed for the septic system, parking or required open space. On the few multifamily lots with real yard area, a pair of small detached units can work, but the site plan has to prove the septic and fire access before anything else.

Septic Capacity on Malibu Apartment Properties

Wastewater is the main limit on adding units to a Malibu multifamily property. Most of the city has no sewer, so apartments rely on onsite systems that were sized for the original unit count. Each new ADU adds flow, and Environmental Health reviews whether the system can absorb it. Larger systems may also fall under state water quality oversight, which adds its own requirements.

We start every multifamily ADU study with the septic records and, where they are incomplete, an inspection by a qualified septic professional. If the system cannot take more flow, the options are an upgraded or advanced treatment system, fewer units, or smaller units with fewer fixtures. That decision shapes the rest of the project.

Building ADUs Around Tenants in Place

Most multifamily ADU projects happen while the existing units are occupied. Converting a carport or storage room near tenant entries means planning for noise, dust, temporary loss of parking or storage and short utility shutoffs. We schedule loud work for reasonable hours, keep exit paths clear and give notice before any interruption to water or power.

Fire separation between the new ADU and existing units is a central part of the design, especially in older buildings. Upgrading alarms, rated assemblies and exit routes for the new unit can also improve conditions for the existing tenants.

Sequencing helps. Where a property has both conversions and new detached units planned, we often finish the conversions first so tenants see the disruption end in one part of the site before work begins in another. Permits can be pulled together or in phases depending on financing and how the owner wants to manage vacancies.