How does the ADU design and permit process work?

Mar 31, 2026

First you must determine if your project is to build a brand new ADU or is it a garage conversion to an ADU. A new build is a bit more complex since the structure will have to be in line with new building codes, whereas a garage conversion is simpler since the structure is already there. Regardless, as in any large projects, the process starts with a consultation done by an ADU expert or an Architect, you will need to specify your goals and let the professionals lead the way. Once you reach an agreement, you want to see an initial design (Better in 3D), a conceptual drawing that shows the location, size and layout. Once that is achieved and agreed upon the architect will complete the drawings and submit the full architectural set to the local planning and building department. Depending on the specific city and the complexity of your project, the pre-construction phase, including design and permitting, typically spans 30 days to 3 months. Please note that projects requiring review boards or those in cities with complex permit processes may fall outside this standard window. After the plan is approved your selected contractor can pay the fees on your behalf and obtain the building permit or, you can do this yourself as an “owner-builder”.