ADU Builder in Calabasas for Design, Permits and Construction

Calabasas Lot Types and the City's ADU Rules

Lots in this city fall into a few broad groups. Hillside parcels in Calabasas Highlands and along Old Topanga Canyon Road sit on real slopes, where a level pad costs money. Park Moderne, the 1920s community behind Calabasas High School, was laid out on 5,000 square foot lots, so every foot of side yard counts. The master-planned tracts off Parkway Calabasas, Las Virgenes Road and Lost Hills Road have flatter pads, attached garages and HOA design rules. Each group points toward a different ADU type.

Inside the city, ADU permits are the job of Community Development at City Hall. Its Planning Division checks zoning and the Building and Safety Division, at 100 Civic Center Way, issues the building permit. The local ADU rules sit in Municipal Code section 17.12.170, with a standards table in section 17.11.170. As quoted by the state in 2026, that table held detached ADUs to one story and 16 feet and capped structures at 30 percent of the rear yard.

Those local rules are in flux. In a May 4, 2026 letter, the state Department of Housing and Community Development (HCD) found the City's 2020 ADU ordinance out of compliance with state law. It flagged a separate zoning clearance step, a ban on selling an ADU apart from the house, and a design standard requiring ADUs to conform to the main home, which HCD called subjective. Where a local rule conflicts with state law, state law controls, and we check the current code at the start of design.

Fire exposure is the other constant. CAL FIRE published the current Fire Hazard Severity Zone map for Calabasas on March 24, 2025, and much of the city's hillside edge carries a Very High rating. In that zone an ADU must use wildland-urban interface construction (ignition-resistant siding, ember-resistant vents, tempered glazing) and the lot needs maintained brush clearance. The 2018 Woolsey Fire, which jumped US 101 near Calabasas overnight, is why the fire department takes those details seriously.

Calabasas ADU Cost Drivers, Lot by Lot

Published price ranges would mislead you here, because two ADUs of the same size here can differ widely in cost. The first driver is type. Converting a garage or an existing room reuses a slab, walls and roof, so it usually costs less than a new detached building. A second-story unit adds structure, stairs and fire separation. Size matters less than people expect, because kitchens, bathrooms and utility work cost about the same whether the unit is 450 or 800 square feet.

The site is the second driver, and in Calabasas it is often the biggest. A sloped lot may need a soils report, a retaining wall, caissons or a stepped foundation. A narrow side yard can force hand-carried materials or a crane. Distance to the sewer line, the condition of the existing lateral, and whether the main electrical panel can take another load all shape the budget. Water and sewer come from Las Virgenes Municipal Water District, and power comes from Southern California Edison, and each has its own connection rules.

The rest comes down to code and choices. Very High fire zone construction adds material cost. HOA architectural review can add a design round. Finish level, from cabinets to flooring, swings the total. Fees help small units: an ADU of 750 square feet or less pays no impact fees, and larger units pay fees scaled to the size of the main house. We walk through each of these drivers at the consultation so the budget reflects your lot.