ADU plan submission diary - San Mateo, CA

[David Song]

I am in the process of applying for an ADU in san mateo, ca. I saw a lot of people interested in this topic, especially in bay area, CA. I am going to document my experience with this ADU here, so other people might find it useful.

This is the exterior of the front of the house, which was remodeled in 2011-12 completely.

The backyard is pretty big, and the proposed ADU is 640 sf detached from existing.

The original plan was submitted and comments come back with some planning questions about size of the lot, setback requirement etc. After a phone call with the planner, it turned out to be OK.

The second obstacle is the property is located in a flood zone border. Therefore, the minimum elevation need to be above the flood plain. We did have a elevation survey conducted 4 years ago, which shows that the ground level in the backyard is actually at the base flood elevation (BFE). Therefore, we plan to use a perimeter foundation with 18-24" above ground, and a crawl space (where no electrical wires are allowed).

Yesterday, I got a phone call from San Mateo city asking about fire sprinkler system. I told them that it is my belief that FS is not required for ADU, based on state law.

Today I received a email from the city attaching a guidelines for determination of sprinkler requirements handout, which shows a table indicating that the city requires detached ADU with a FS, no matter whether the existing structures has it or not.

I just send back an email attached the state fire marshal info bulletion IB 17-001, which specifically exempt detached ADU where existing structures does not have FS, and requested that requirement be waived.

I will see how it goes and keep this diary as we move forward.