Attached ADUs and Additions in Beverly Hills

When an Attached ADU Beats a Detached One in Beverly Hills

Plenty of Beverly Hills backyards are already spoken for. A pool, a tennis court, mature oaks or a cabana can leave no clear spot for a freestanding building. Adding onto the house uses the side yard or a corner of the rear yard instead, and it keeps the open lawn intact.

Attached units also suit lots where the yard is shallow, which is common south of Wilshire. And on hillside parcels, where the city's Hillside Area guide asks for a 100-foot front setback before a larger detached ADU can be built, extending the existing house can be the one way to add real square footage without starting a discretionary review.

Beverly Hills Code for Attached ADUs

In Beverly Hills, an attached ADU is built under BHMC 10-3-5001, the same section that covers the larger detached type. For a Central Area lot, that puts the ceiling at 1,400 square feet if the house is above Santa Monica Boulevard and 1,200 if it is below, trimmed further when the lot is short on floor area. The 800-square-foot floor is protected regardless of floor area, lot coverage and front setback limits.

Height follows state law as a floor. The state lets an attached unit rise as high as 25 feet unless the zoning sets a lower ceiling, and two stories is the most a city has to permit. Where an owner wants something larger than the objective standards allow, the city's Minor Accommodation Permit is the discretionary route. Review is ministerial and takes place in Building and Safety plan check. The city asks owners to consult a planner first, and on attached work that meeting is especially useful, because the planner can flag how the addition interacts with the main house's existing permits.

Tying an ADU Into an Older Beverly Hills House

The hard part of an attached ADU is the connection. The new wall has to meet the old one with a proper fire separation, a sound assembly between the two homes, and a roofline that sheds water instead of trapping it. On a 1920s Spanish revival house with a clay tile roof and thick plaster walls, that joint takes careful detailing. We open up the existing structure early to see what is there. Older Flats homes can have undersized footings, old knob-and-tube circuits or galvanized supply lines in the wall we plan to touch. Finding those during design costs far less than finding them mid-framing.

The two units can share utility services or have separate ones. A shared electrical service often needs a larger panel. Separate meters for SCE power or city water add coordination but give a tenant their own bills. We price both options during design so the choice rests on real numbers.

• Fire-rated wall and floor assembly between units
• Sound insulation at the shared wall
• Roof tie-in matched to tile, slate or composition
• Separate exterior entrance for the ADU
• Panel capacity check for a second kitchen

Attached ADU Layouts That Work on Beverly Hills Lots

The most common layout we draw is a single-story wing off the rear of the house, with the ADU entrance facing a side yard and a private patio. Another is a wing along the driveway side, set back from the front so the street view does not change. On lots with an attached garage, part of the addition can wrap the garage, turning a conversion and a small addition into one unit.

Second-story attached ADUs are possible, especially north of Santa Monica Boulevard, but they need a structural review of the existing first floor. In Trousdale Estates, where the code caps structures at 14 feet, a second story is off the table and every attached unit stays on the level pad.