My wife and I bought a home in San Diego, CA that has an additional dwelling unit (ADU). We are house hacking and living in the ADU. The ADU is not viewable from the front of the property, so I wanted to make a separate mailbox/mailing address for it. I couldn't find much on the internet for how to do this, so I figured I would write about my experience. The process may vary from county to county or state to state.
First, I called the city asking how to create a new address. The first person I spoke with informed me that it is completed through the United States Postal Service, not the city. I had a hunch that the employee could be wrong, so I went to the city website and found a “contact us” link. There it let me write a message and leave my contact number. I submitted my question regarding the new address and a few days later I got a call. It was a member from the engineering department of the city and she walked me through how to obtain a new address. I submitted the required documents (literally a screenshot of google maps pointing out the property lines) and waited for a response. It took about a week or two before hearing back, but eventually I received a form stating that the city has created a new address and have forwarded the information to USPS.
Since creating the new address, the mailman has been a bit confused but overall we're receiving our mail. Please be aware that you should ensure that your ADU is permitted prior to going to the city. When I contacted the city they had mentioned that it's no problem to create the new address because the ADU is permitted. I didn't bother to ask what the case would be if it wasn't permitted, but I can't imagine drawing attention from the city that you have an unpermitted living space is ever a good idea.
I hope this helps and happy house hacking :)
In my city, there is an office that assigns "certified addresses" for all the city services, such as building permits, 911, trash pickup, etc. They even handle apartment numbers.
Apparently they constantly emit their updates which are picked up by all the utility companies, USPS etc. You get it through the city "map room". Your city likely has something similar. If the ADU is legal and already exists, it may already have been assigned an address.
This can be a difficult nut to crack sometimes. I have had new addresses issued and then the Post Office is given bad information or it's lost in translation. Thanks for sharing!
The standard process here is to assign either an address number (if it's a separate building) or a unit designator anytime plans are approved for a permit. There's literally a department called "MIS Addressing" that handles this - you'll get the assigned address back along with other reviewer comments.
How someone permitted an ADU and didn't get an address (if done in the past 15 years, at least) is lost on me. But, good to know they took care of it for you!
The city assigned an "A" to my address for the ADU during permitting.