California made ADUs far easier to permit, but the process still surprises people. Here is what actually happens between the idea and the keys.
Accessory dwelling units have gone from a planning-department headache to something California actively encourages. State legislation has stripped out many of the local barriers that used to kill these projects, and for homeowners across Solano, Napa and Yolo County an ADU is now one of the few reliable ways to add substantial value or rental income to land you already own.
The first question is always feasibility, and it is worth answering honestly before anyone gets attached to a floor plan. Setbacks, lot coverage, existing utility capacity, sewer connection points and access for construction equipment all determine what is realistically buildable. We walk the lot early and tell you plainly what will work — including when the answer is that a garage conversion makes far more sense than a detached build.
There are broadly three routes. A garage conversion is usually the least expensive because the foundation, walls and roof already exist, though it costs you the garage. An attached ADU shares a wall with the main house and can tie into existing utilities more easily. A detached ADU costs the most and delivers the most, because it functions as a genuinely separate residence with its own privacy and its own rental appeal.
On timeline, the honest answer is that design and permitting typically take three to six months, and construction another four to eight months depending on size and route. Anyone quoting you a finished ADU in three months is either not counting the permit phase or has not run one before. The permit stage is largely outside a contractor's control, which is exactly why it should be planned for rather than wished away.
Budget conversations should include the items that sit outside the building itself. Utility connections — particularly sewer laterals and electrical panel upgrades — are a frequent and significant surprise. Many older Solano County homes have panels that simply cannot carry a second dwelling, and that upgrade needs to be in the budget from day one rather than discovered at rough-in.
Site work matters too, and it is where we have an advantage. Foundations, slabs, driveways and walkways are handled by our own C-8 concrete crews rather than subcontracted out, and the flooring, painting and finish carpentry are all in-house as well. That removes most of the coordination gaps where ADU schedules typically slip by weeks.
We build ADUs and ground-up structures under our B general building licence, CSLB #994790. If you are considering one anywhere in our service area, the useful first step is a site conversation — no drawings needed. We will tell you what your lot can take, roughly what it costs, and how long it will genuinely take.
