ADUs & Additions in Topanga

Los Angeles County Department of Public Works, Building and Safety Division. Topanga is unincorporated, so building permits come from the County Public Works Building and Safety Division. Most of the canyon lies in the Santa Monica Mountains Coastal Zone, where Regional Planning issues coastal development permits under the certified Local Implementation Program; parcels at the northern end fall outside it, in the Santa Monica Mountains North Area. Improvements to an existing, lawfully established home, pools included, can be exempt from a coastal permit, but not in H1 or H2 habitat, in an area designated as highly scenic, or where a septic system is added or expanded. Grading of 50 to 5,000 cubic yards needs a minor coastal permit, and grading is prohibited from October 15 through April 15 except in limited cases. The program allows only one accessory dwelling unit or guest house per property, at no more than 750 square feet, on a septic system separate from the main house and outside H1 habitat, its buffer and the Quiet Zone, and each one must retire a transfer of development credit. We prepare the drawings, make the submittal and handle plan-check corrections ourselves, so you are not the one chasing plan check.

Two patterns: the rural villages of Fernwood, Old Topanga, Topanga Oaks, Topanga Woods and the Old Post Office Tract, which the coastal program defines as antiquated mountain subdivisions, many created in the 1920s and often lacking infrastructure built to current standards, and scattered hillside parcels on the slopes between them. In the villages, new development must be sited to avoid oak woodland, and where removal cannot be avoided it may not exceed 10 percent of the oak woodland on the property. Where new residential development is approved in H2 or H3 habitat, the building site, counting graded slopes, structures, decks, patios and other hard surfaces, is capped at 10,000 square feet or 25 percent of the parcel, whichever is less. One local condition that shapes the work: CAL FIRE's State Responsibility Area map places nearly all of Topanga in a Very High Fire Hazard Severity Zone, and the coastal program asks new construction there for fire-resistant exterior materials, windows and roofing, with eaves and vents that resist flame and embers; County Fire fuel modification can also reach beyond the approved building site.

All of it, including Fernwood, Old Topanga, Topanga Oaks and Topanga Woods. Our crews run every job out of our Cahuenga Pass base in Los Angeles, with our own people on site.

Detached ADU: generally $150,000 to $400,000+ across Southern California. What moves it is square footage, finish level, utility runs, and site access; garage conversions typically run well below a ground-up detached build. We give line-item pricing after seeing the site rather than quoting a number over the phone.

Plan a realistic year. Design and engineering typically take one to three months, city plan check and corrections add several more, and construction usually runs four to eight months depending on size and site access.

Usually yes, and often substantially, because the foundation, walls and roof already exist. The trade-offs are that you lose the garage, and older slabs and framing sometimes need upgrading to meet current code.

California ADU law is designed to allow long-term rental, and an ADU is one of the few ways to add rentable square footage to a single-family lot. Short-term rental rules vary by city, so confirm your local ordinance before counting on that income.

Yes. Plans, engineering, Title 24 and the city submittal are all handled in-house, including responding to plan-check corrections. That is a service we sell on its own, so it is not something we hand off.