ADU Guides

A second unit is the most common way to add usable space to a property in this part of Los Angeles County, and it is also the most misunderstood. California law now requires cities to approve a compliant application ministerially, against objective standards and without a discretionary hearing, which is why so much ADU content online reads like a legal summary rather than practical advice. The guides in this section are the other kind: what the unit actually costs once utilities and finishes are counted, how long review takes in practice, what size and setback limits mean for a specific yard, and which type suits which lot.

Three things decide most projects before any rulebook does. Lot coverage, because a house that has been added onto for decades may already be close to its limit. Utilities, because a separate dwelling is a separate sewer and electrical load. And access, because equipment has to get down the side of the house before anything can be built at the back. We measure all three before drawing anything, which is why the guides here keep returning to measurement rather than to regulations.

Start with size limits and setbacks and the ADU cost table. Then decide between the types: garage conversion vs detached ADU, JADU vs full ADU, or ADU vs a home addition. Ready to build? Our ADU construction service in Arcadia covers detached units, attached additions and garage conversion ADUs.