How Zoning Works: ADU’s (Accessory Dwelling Units)

Accessory dwelling units (adu’s) were permitted years ago as carriage houses, but were not permitted in the old zoning code. Now, in the new zoning code, they are permitted again. Adu’s must have their own address and can be rented, but they can’t be sold. Also, they have the same type of restrictions as the primary structure on your property.

  1. First, to learn more, take a look at the two definitions for an adu in the zoning code. These occur on pages 11.12-30 and 13.3-1. There are variations but 99% of all adu’s are apartments over a garage.
  2. If it’s a detached adu, as in a separate building or over the garage, you can learn more by seeing page 5.3-35.
  3. A detached adu can be 1 ½ stories and 24’ high. As with the garage, the vertical leg of the bulk plane is 10’ with an inward slope of 45 degrees from the top. The requirement for 1 ½ stories means that the upper floor area can only be a maximum of 75% of the area of the ground floor.
  4. To make the adu more visible to emergency vehicles, the building has to touch the south side set back line.
  5. Lot sizes are limited in the same way as the house lots except that we get a 50% exception for land coverage, up to a maximum of 500 sf. The exception doesn’t apply unless we are 15’ from the main house, and at least 80% of the ground floor is used for parking. (ie. a garage)
  6. If located in the rear 35% of the lot, the side lot and rear setbacks are 5’, unless the lot is <30’ wide. If less than 30’ the side lot setback is 3’.
  7. In addition to the above, the land coverage (footprint) is limited to 650 sf if the lot is <6,000sf. The coverage is 864 sf if the lot <7,000sf and 1,000 sf if the lot > 7,000sf.

Please let me know if you have any questions regarding the above.

Steve Culbertson