There are a few circumstances that allow ADUs to be over 16 feet in height:
1. Sites with an existing or proposed multifamily, multistory dwelling
Detached ADUs may be up to 18 feet in height on a lot with an existing or proposed multifamily, multistory dwelling. Multiple detached single-family houses on one lot do not qualify as a multifamily lot.
2. Attached ADUs
Attached ADUs may be up to 25 feet tall or the height limitation that applies to the primary dwelling, whichever is lower.
3. Senate Bill 897: Allowed ADU Height Within 0.5 miles of Major Transit Stop and High-Quality Transit Corridor
SB 897 allows an 18-foot tall detached ADU on a lot that is within one-half mile walking distance of a major public transit stop or a high-quality transit corridor, as defined in Public Resources Code Section 21155 (plus an additional two feet in height to accommodate a roof pitch on the ADU that is aligned with the roof pitch of the primary dwelling unit).
There are three major transit stops in Richmond:
El Cerrito Del Norte BART Station (6400 Cutting Blvd, El Cerrito, CA 94530)
BART Richmond Station Park and Ride (1508 Macdonald Ave, Richmond, CA 94801)
Richmond Ferry Terminal (1453 Harbour Way S, Richmond, CA 94804)
There is one high-quality transit corridor in Richmond:
San Pablo Avenue (in areas where Lines 72, 72M, and 72R intersect).