Building an ADU Above the Garage in Calabasas

Calabasas Height Rules for Second-Story ADUs

The City's ADU standards table, as quoted in HCD's 2026 review, held detached ADUs to a single story and 16 feet. Under that rule, a new apartment stacked on a freestanding garage would not pass, because the garage alone uses most of the height. State law only promises detached units a 16-foot minimum in most locations, with 18 feet near major transit, so it does not force the City to allow a second floor on a detached building.

Attached units follow a different state standard. Connect the unit to the house, though, and California lets it climb to 25 feet and two full stories, unless the zone sets a lower cap. That makes the attached garage the more promising base for a second-level unit in Calabasas. Because HCD found the City's ordinance out of compliance in several respects, we check whether the detached height rule has changed before ruling anything out.

Building an ADU Over an Attached Garage in Calabasas

Many homes in The Oaks, Mulwood and the other planned neighborhoods have a two- or three-car garage attached to a one-story wing of the house. A second floor over that garage, reached by an exterior stair, can hold a one-bedroom unit with views over the rooftops toward the hills. The garage stays a garage, and the yard stays a yard.

Privacy deserves early thought. A raised unit can look straight into a neighbor's yard, and HOAs in Calabasas often have view and privacy guidelines. We set window sills, use clerestory glazing toward close neighbors, and place the deck or landing where it faces your own property. Those choices also tend to smooth association design review.

Structure and Fire Separation for an Above-Garage ADU

Garage foundations were sized for a roof, not for a second floor full of people, furniture and a kitchen. We usually find that the existing footings need reinforcing or that new footings must go in, along with new posts, beams and shear walls to handle seismic loads. A structural engineer designs that system, and a soils report may be required on hillside lots.

The floor between the garage and the living unit must be a fire-rated assembly, and the stair and landing need to meet egress rules. On parcels in a Very High Fire Hazard Severity Zone, the new upper walls, eaves, vents and windows also meet wildland-urban interface standards. Fire sprinklers may be required depending on the project and the existing house, and we confirm that during plan check.

Two-Story ADUs Outside the City of Calabasas

Not every nearby community uses Calabasas' rules. Woodland Hills and West Hills fall under the City of Los Angeles, which has its own ADU ordinance and its own height and hillside provisions. Hidden Hills runs its own city permit process. Bell Canyon follows Ventura County standards, and Monte Nido answers to Los Angeles County. A two-story ADU that is off the table in one jurisdiction may be allowed a few miles away.

When a client owns property across one of those lines, we start from that agency's code rather than assuming the Calabasas limits. The design questions stay the same, including structure, stairs, privacy and fire construction, but the height envelope changes.

Utilities for an Upper-Level ADU

Plumbing has to climb, which is easier when the unit sits over a garage that backs up to a house bathroom or laundry. Drain lines drop through the garage ceiling and walls to the existing sewer lateral. A heat pump water heater can go in a closet upstairs or in the garage below. Electrical service often needs an upgrade or a subpanel to carry a second kitchen and heat pump, and we coordinate that with Southern California Edison if the service itself must grow.