The lack of affordable housing in our area is apparent even if if you have not tried to buy or rent in recent years. We used to think the commute from La Honda over the hill was far (but worth it!) but nowadays you might even work with someone who commutes daily to the Bay Area from the Central Valley. Maybe your children have had to move to another state to afford their own home. Accessory Dwelling Units (ADUs) may provide some relief to our housing crunch. The California Health and Safety Code now “requires that cities and counties develop a plan that incentivizes and promotes the creation of ADUs that can be offered at affordable rent for very-low to moderate-income households.” Locally the ADUs are allowed in our unincorporated area on R-1 zoned properties.
This link will take you to the California Housing and Development page with all sorts of information from the viewpoint of the State of California, including a handbook with frequently asked questions.
This image is from the San Mateo County Second Unit Resource Center
Although they may be labeled with other names in other areas, San Mateo County is using the term ADU or Accessory Dwelling Unit for these small units. They range from a detached “granny unit” to a section of your existing home with its own entrance and sleeping and cooking areas. (Please note, the units are not to be used for B&B type rentals.) If you are building a new home, you can also include and ADU in the construction plan.
This link will take you to a short list of the standards required in San Mateo County.
The state mandate has brought about the relaxing of some requirements for building an additional unit on your lot in a city or unincorporated residential area (as in the case of La Honda and other Coastside communities). So don’t discount the program if you had looked into it previously and were told you could not build. it is interesting to note that at this writing, notification of your neighbors during the permitting process is not required, although it is recommended as the neighborly thing to do.
The San Mateo County Ordinance can be viewed or downloaded here.
The program is still so new that it might take a little digging to find the specific information you require. But there is plenty of help out there to get your project underway, including fast tracking of permits, and grants in some cases to help with the fees involved.
A good starting point might be the Second Unit Resources Center for San Mateo County, You will find links to resources and even a calculator to help you with an idea of the cost.
If you do a web search on "ADU" and "San Mateo County" you will find many links to private companies who want to "help" you on your ADU journey!
And for those who may have an unpermitted additional living space, you should check out the San Mateo County Second Unit Amnesty Program:
While most accessory dwelling units in the County are built with all required permits and approvals, there are also some units that have been constructed without following the required procedures. Some of these units may be safe and fully habitable, and simply did not receive proper permits; in other cases, the standards of construction may not meet code requirements, and may present health and safety issues to residents and adjacent properties. The Accessory Dwelling Unit Amnesty program is intended to provide a low-cost, penalty-free pathway to improve all unpermitted accessory dewlling units to a safe and habitable condition, without requiring removal of the units or displacement of any residents.
Check out the amnesty program here!
Good luck if you choose to investigate a second unit. There's lots of help out there!