Community Development

So, you want to build an ADU— What is it and what is the process?

An accessory dwelling unit (ADU) is a small, self-contained residential unit located on the same lot as an existing single-family home and subordinate to a single-family dwelling unit. An ADU has all the basic facilities needed for day-to-day living independent of the main home, such as a kitchen, sleeping area, and a bathroom.

ADUs can expand the range of housing choices for residents in the city, as well as helping residents age in place, adding space to house extended family, offering an avenue for rental income, and more. Developing an ADU can seem daunting, but you are not alone. We have outlined the process in four easy steps below.

Step 1: Check the map.                                                                       
ADUs are permitted in all residential single-family zones (Ferndale Municipal Code 18:33— RS low, RS medium, and RS high). These zones are highlighted on the City GIS maps (www.cityofferndale.org/maps) in three shades of yellow on the “Official Zoning” layer.

Step 2: Check the code.

Ferndale Municipal Code 18.34 outlines a number of criteria for the construction of an ADU. Each must be met before an ADU
application is approved. Most importantly:

• Only one ADU is allowed per lot as an accessory use to a single-family home.
• The ADU maximum size shall be no more than 50 percent of the square footage of the existing residence or 800 square feet, whichever is less.
• The ADU may not be segregated in ownership from the principal dwelling unit.

Step 3: Apply for a permit.
Before any construction can commence, the property owner must obtain a building permit and indicate on the application form that the use is an ADU. All the City’s permits are applied for online through the permit portal, which is available here.

How much does it cost? The final permit cost will depend on the size of the ADU and the total project valuation. Typically, an ADU permit is $3,000-$8,000 including ALL relevant impact fees with the average permit ending up less than $5,000.

Step 4: Build it and Enjoy!
For more information about the ADU process, and online application forms, please explore the City website or contact the Community Development Department at 360-685-2379 or  ruthhohman@cityofferndale.org.