ADU How-To
What is an ADU?
An Accessory Dwelling Unit (ADU) is a smaller, independent residential unit located on the same property as a primary home. ADUs provide additional housing options while allowing property owners to make more flexible use of their land.
An ADU generally includes its own living space, kitchen, bathroom, and sleeping area and may be located within, attached to, or separate from the primary residence.
Common types of ADUs include:
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Attached ADUs: Added onto or connected to the primary home.
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Detached ADUs (DADUs): Separate structures located elsewhere on the property, sometimes called backyard cottages.
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Interior ADUs: Created within an existing home, such as a converted basement or portion of the house.
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Garage conversions or above-garage units: Existing or new garage space converted or designed to include a separate dwelling.
ADUs can provide housing for family members, create rental opportunities, help homeowners age in place, and add more housing choices within existing neighborhoods.
Pre-Approved ADUs
The Kitsap Building Association has collaborated with Artisans Group Architecture + Planning to provide pre-approved ADU designs for Kitsap residents.
A pre-approved ADU plan is a building design that has already undergone an initial review. Kitsap County, and each of the cities within, offer FREE pre-approved ADU designs intended to make the process easier and less expensive for homeowners. The plans are available for a $1,000 fee if your property is located outside a city, or outside an Urban Growth Area (UGA).
CLICK HERE to use the Kitsap County guide & see if the free plans are available to you.
Cost
The cost of building an ADU can vary greatly from one property to another. There is no single “average” price that will accurately predict every project. The final cost depends on the size and design of the ADU, site conditions, utility connections, permitting requirements, construction method, materials, finishes, and the amount of site preparation required.
For example, a flat property with no critical areas nearby and has water and sewer connections may be considerably less expensive to develop than a property that requires extensive excavation, a septic-system upgrade, long utility runs, retaining walls, or specialized environmental review. Likewise, converting existing space into an ADU can have a very different cost than constructing a new detached unit.
Below are some estimated figures to help you understand your total budget:
** For a better sense of how much your specific project may cost, you may want to contact and architect or designer.
Timeline
The timeline for ADU construction also varies widely, depending on the project. Below is an estimate of how long it will take to build an “average” ADU.
How-To Steps to Building an ADU
This guide is designed to help homeowners & community members better understand Accessory Dwelling Units (ADUs), and the basic steps involved in planning & building one.
ADU requirements can vary depending on the property and local jurisdiction, and the permitting process can be difficult to navigate. This guide brings together key information on ADU types, permitting, design, utilities, costs, and local requirements to help you understand what to expect and where to start.
The goal is not to replace guidance from your local permitting agency or qualified professionals, but to provide a clear starting point that helps you ask the right questions, identify potential requirements early, and move through the process with greater confidence.
If at any point in the process you would like professional assistance planning, designing, permitting, or building the right ADU for your property, visit our Request for Proposal (RFP) Portal. Share some details about your project & select the type of professional you would like to connect with. Your request will then be shared with qualified KBA members who may be able to assist with your project. Your local Department of Community Development (DCD) can also assist you, and their contact information can be found near the bottom of this guide.