What Exactly is an Accessory Dwelling Unit?

If you are interested in turning a structure in your backyard into a rentable space to bring in more income or have an extended family member or adult child move in while still giving them their own space you have probably run into the term “Accessory Dwelling Unit” or ADU.

What exactly is classified as an ADU? What are the specific conditions of having an ADU on your property? Let’s take a look at the three most frequently asked questions about ADU’s and what the answers are for right here in Snohomish County because the answers change depending upon the county and sometimes even the city you live in.

What Specifically is an ADU in Snohomish County?

An accessory dwelling units in Snohomish County are referred to as “Accessory Apartment Attached” and “ Accessory Apartment Detached”

Accessory Apartment Attached: this is the term used in Snohomish County in reference to a dwelling unit that is in the same structure as, under the same ownership as, and subordinate to an owner-occupied single family dwelling unit. In simpler terms this refers to rental units that are attached to or inside of your primary home.

Accessory Apartment Detached: according to the county this is a dwelling unit other than a mobile home which is located on the same lot and under the same ownership as, and subordinate to, an owner-occupied single family dwelling unit. In simpler terms this is a building placed on land within the borders of your property that you own in addition to your house with intent of someone living there.

Are ADUs Permissible in Snohomish County?

Accessory apartments as Snohomish County calls them are allowed in almost every single family and multifamily residential urban zone of Snohomish County. Before building an ADU either inside your home or in your yard, you should make sure your home is within one of these zones. You can check the zoning for your property by visiting the Snohomish County website and searching for your property by address.

It is important to know that it is not enough to have a property in one of these zones to be able to build an ADU in Snohomish County. ADUs are deemed as “Administrative Conditional Use” and require a review or permit by the county. They want to ensure the ADU is in compliance with county codes and regulations.

What are the Snohomish County Requirements for Accessory Dwelling Units?

For the full details on what is required of legal ADUs in Snohomish County it is best to visit the county website and look up Section 30.28.010 and read it thoroughly to know what is required. One big requirement to note is that the owner of the property must either plan to live in the main single-family home on the property or within the ADU. It is not permissible to set up an ADU at a rental property.

If you have read the codes or talked with Snohomish County officials and are ready to move forward with building an “Accessory Apartment Detached” on your property we can help. We have several buildings that can be turned into ADUs or we can design a custom plan for a mini-cabin, shed, or garage apartment.

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