Finding an ADU floor plan online is easy. Finding an ADU floor plan that is actually accepted in your city is harder.

Many homeowners begin by searching for backyard cottage designs, prefab ADUs, tiny homes, garage conversion layouts, or one-bedroom ADU plans. Those searches can produce attractive images, but they do not always answer the most important question: can this plan be used where I live?

ADU rules are local. Even when state law creates a general framework, cities and counties may have their own plan programs, accepted plan lists, permit requirements, and fee notes.…