Here on the Peninsula, people are needing to get creative about housing. With limited space, rising populations and multi-generational families, finding housing that fits your needs can be tricky. San Mateo County is making a considered effort to promote and encourage residents to explore developing second units, or ADU’s. So what are ADU’s all about?
The term ADU stands for “Accessory Dwelling Unit”. This could be anything from a garage conversion to a free-standing structure on the property. Regardless of type, they are all self-contained and smaller than the primary structure on the property. Often known as in-law units, cottages or garage apartments.
ADU’s can be used in a variety of ways. More and more, they are being developed as rental units. Similar to a studio or one bedroom apartment, but with the feel of a single family home. These units can generate great income for owners.
Another common use for ADU’s is for multi-generational housing. For families wanting to have an aging member live with them, but still give them their privacy and independence, an ADU can be the perfect solution.
Not at all! While new construction is certainly an option (and generally required for free-standing units,) other options are to convert a garage into a unit or turn attic space or attached rooms into a separate unit.
Step one is to talk with your city’s planning department and see if ADU’s are allowed, and what restrictions there might be for new builds. All San Mateo County cities have clear guidelines on ADU’s in terms of size, zoning restrictions, and placement on the property.
Yes and no. Your primary house won’t be reassessed (you’ll still keep your original tax basis,) but your ADU will be assessed and added to your existing property taxes.
Keep in mind, if you use the ADU as a rental property, that will impact your income taxes.
With so many variables, it isn’t possible to answer this question simply. ADU’s can be simple room conversions, more complex conversions (such as to a garage,) build of a modular unit or build of a unit completely from scratch. In theory, pricing could range from $25,000 to $200,000 or more, depending on your process, needs and finishes. On average, $400/square foot is a good figure to work with.
Interested in learning more about ADU’s? San Mateo County has a terrific website devoted to them, including having a calculator to determine cost vs income, as well as a workbook for planning your ADU project and information about individual city guidelines. All of this information can be found at .
So what do you think, would you consider adding an ADU?
by Sally Slate Lee
IMPORTANT NOTE: I have not and will not verify or investigate the information supplied by third parties.