ADU plan submission diary - San Mateo, CA

40 Replies

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.

I would love to know more about this and your experience. Please let me know and also look at my blog posting regarding an 1069. 

@Jo-Ann Lapin

I will keep posting here on the progress. It is sometimes surprising that city ordinances are not in line with state requirements. I first learned about the new ADU law from your post on BP. Thanks a lot.

@Henry Pho  I was considering freak, if the cost justifies it. Have not find a reliable fre-fab yet. 

I am a GC myself, so my construction cost may not be much higher than prefab.

This is only 640 sr small house. The framing is pretty standard. 

@Ariel Vincent

All my rentals are unfurnished. I would love to know how you market those furnished rentals to corporate rental? 

I have stayed in a corporate rental in 2003 when I first moved to bay area, in Bridgepointe apartment in San Mateo. I remember that the rental offers topline furniture, cleaning service, and pots/pans, even glassware.

I do not know what is the difference in rental pricing though.

Update on ADU: just got an email from the city reviewer, saying that my email has been forwarded to the deputy fire marshall of San Mateo city for review. Will see how they respond on the FS issue.

@David Song we primarily use Airbnb here in the bay area. We set our minimum to 30 days so we automatically capture anyone looking for longer term stays. I also use CHBO, VRBO and a few others, but Airbnb brings most of my business. I previously worked for HomeSuite which is where I learned how lucrative the model can be. When I came to my current brokerage, I started to build out the furnished rental side of our property management business. 

Pricing depends on many factors and some properties just aren't a good fit for many reasons - the main ones usually being location, access to public transportation, and size. Happy to chat in more detail if you're ever interested! 

@David Song best of luck with fire dept. I'm also fighting them on an asinine request for my ADU (inlaw legalization) in San Francisco. God it seems the fire dept is always so out of it, and they never think practically. They have always been a major PITA in my projects. Like during a lot split project where they forced me to spend > $30k (incl. a new water meter which is $$$) to provide 4 sprinkler heads in a basement hallway. $30k for 4 sprinkler heads!

This time they want me to add a second means of eagerness, which is only available through the garage. This is a triplex, so the 2 car garage becomes 1, with a dorky walk through lane eliminating the 2nd spot. Normally the second means is through the back yard, but they don't like mine because I only have 35', and they want 50'. As if +15' in a yard is going to make any difference. A lot of their requirements are arbitrary IMO.  I call it f*ucked by fire. 

Today, I received an email from city of San Mateo fire department:

"I am in receipt of your request for exception for fire sprinklers for your proposed detached ADU project. We are aware of Senate bill 1069 and it's application to ADU structures however, the city of San Mateo has adopted a more restrictive fire Code ordinance. San Mateo's fire code ordinance (23.28.160) requires all new structures in excess of 400 square regardless of occupancy classification to be sprinklered. There are no appeals per fire code ordinance section 23.28.050 "All decisions and determinations of the Fire Chief decisions or determinations made by the building official relative to the application and interpretation of these codes are final and not subject to appeal".

Please let me know if you have any questions.


Does that mean even with state law SB 1069, the local city can still go the other direction?

If that is the case, why do we need SB 1069 anyway.

@Henry Pho I manage some that the owners have furnished themselves but I know other people who have furnished from Ikea, Ashley furniture, and even Cort. Cort can be great because they sell off their older furniture that they no longer rent, but in my opinion the aesthetic looks just like a hotel and that is not what I'm going for so I stay away from them. It's been successful for others I know here though.

@David Song I would suppose that SB 1069 covers all of CA and if a local ordinance doesn't say otherwise, then SB 1069 is the law. It's the same as how CA has its own rental laws, but cities and counties can enforce their own policies such as rent control.

@David Song ok looks like it's time to show the unit as 399 sq ft on your plans ;)  Maybe there is some way to have non liveable sq ft added back to the unit after final inspections?

Time to get creative!

@Amit M.

I am not that concerned about sprinkler, we have done a commercial unit for a client before. The cost is a few k with new system for a 1500 sf unit.

Our ADU is so small and new construction, so putting a sprinkler in is not a big deal. I am just a little pissed that the city is disobeying the state law.

We are going to do a deferred submital for the sprinklers.

@David Song but do you already have an adequate water meter installed at the property? And you're just adding a sprinkler system to existing water meter? PGE is a major PITA if you need to add a separate water meter at the street, takes along time and is $$$. Maybe it's a bigger deal for 3-4 units, which is what I've had to deal with. 

@David Song hi David, I'm curious what state law say about sprinkler requirements? Because in SF if you go from R3 (SFH and duplex) to R2 (3 units and upwards), you need to sprinkler, which really sucks.

If you have any links, etc. that discuss the sprinkler requirements I’d be interested in seeing that. Cheers

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