Building An Accessory Dwelling Unit (ADU)

What is an ADU?

An “Accessory Dwelling Unit” can take many forms and may be referred to by many names: carriage house, backyard bungalow, garage apartment, in-law suite, alley flat, garden-level apartment, etc. An ADU can be either attached or detached from your principal dwelling. It can be located in the basement, over or attached to a garage or other workspace, as an addition, or standing on its own. An ADU can be a great way for homeowners to provide independent housing for a family member or to gain supplemental income as a rental unit for others.

Can I build an ADU on my property?

ADUs are allowed in any zone district with administrative approval, and provided that all applicable dimensional and review standards can be met. One ADU may be built per lot regardless of density requirements, as long as there is an existing associated principal dwelling on the lot. Applicants will require building permit to begin construction, and system development (tap) fees for sewer and water are required prior to certificate of occupancy. Currently, tap fees are equal to 40% of those for a single-family dwelling.

What other zoning standards will I have to follow?

• Detached ADU’s no taller than 15 feet may include up to 1,000 square feet of conditioned living space
• Detached ADU’s taller than 15 feet are limited to 800 square feet of conditioned living space
• ADU’s must be subordinate in size to the principal dwelling and no taller than 25 feet
• Building lot coverage cannot exceed that allowed in the zone district
• Building setbacks must meet the minimums for the zone district
• A minimum of one on-site parking space must be provided for the ADU, in addition to required parking for any other dwellings
• The ADU may not be condominiumized or sold, and it may not be short-term rented (less than 30 consecutive days). 

The following forms must be filled out in order to process an ADU application. Please use the ADU Requirements document to fill in the Administrative Review Form on how you meet the standards of the code section.