Accessory Dwelling Units Tip Sheet

Click here to open a PDF version of this tip sheet.

What is an Accessory Dwelling Unit (ADU)?
An ADU is a second, smaller dwelling unit located on the same lot as a primary residential building. ADUs are intended as a housing option that can contribute to housing affordability and choice, respond to changing household needs and lifestyles, contribute to housing supply, and contribute to neighborhood stability consistent with residential neighborhood patterns. ADUs can be located either within or attached to the primary structure, or in a detached structure in the rear yard.

Where ADUs are allowed. Two ADUs per lot are allowed as an accessory use to a primary residential structure, on legally established lots (irrespective of lot size or width) in zoning districts that permit residential development.

An attached ADU (Dalton home, www.accessorydwellings.org)

 

A Detached ADU (Photo by Lauren Flemister, City of Tacoma)

Development Standards

Size. The living area of the ADU, excluding any non-living areas, is limited to 1,000 square feet.

Height. ADUs are subject to the standard height limits of the zone they are in.

Setbacks & location. Attached ADUs are subject to the primary structure setbacks. Detached ADUs must:

  • Be on the same lot as the primary structure.
  • Be in the rear yard of the primary structure.
  • Provide a minimum of 5 feet from side property lines. If a main entrance faces a side property line, it must have an 8-foot setback.
  • Provide a minimum of 15 feet from the rear property line, except no setback is required from alleys.
  • Meet Building Code fire separation from other structures.
  • Meet building type standards (TMC 13.06.020).

Parking. Parking is not required for ADUs. If parking is proposed, it must be located in and accessed from the rear portion of the lot. The addition of an ADU may not remove parking required for the primary dwelling.

Open Space. The overall site must maintain or provide at least 10% of the lot size as usable and functional yard space (per TMC 13.06.020).

Walkways. For ADUs with a separate entrance, a walkway must connect to the nearest public sidewalk or right-of-way.

  • A minimum 3-foot walkway width is required.
  • Walkway materials must be distinct from any adjacent vehicular areas (may function as a shared drive/walk space along an exterior edge of a driving surface).

ADUs must meet the design standards of the builidng type within which they are located..

Other Requirements.

  • ADUs shall include facilities for cooking, living, sanitation, and sleeping.
  • A separate address visible from the street is required.
  • Occupancy and minimum room dimensions shall meet Tacoma Municipal Code 2.01.060 sections S and T.
  • Construction code standards include minimum ceiling heights, minimum insulation, WSEC energy credits, fire separation, bedrooms emergency escape, smoke and carbon monoxide alarms.
  • Each dwelling needs access to maintenance and control their own heating and water heater.
  • Attached ADU’s need interconnected smoke and carbon monixide alarms.
  • Utility services are required per City standards and need external service connections to sewer and water outside each detached unit.
  • Standards for home occupations, short-term and long-term rentals apply.

Permit Requirements

Construction permits are required for creating, converting, or legalizing an ADU. The type of permits are dependent on the scope of the project, and could include: Building, Plumbing, Mechanical, Site Development, Side Sewer, Stormwater, Water and/or Electrical.

Applicable Regulations
Tacoma Municipal Code (TMC) Section: 13.06 Land Use Code, TMC Title 2 Building and Plumbing Code, TMC Title 12 Utilities.

Submittal and Review Process
Application materials must be submitted in electronic PDF format on compact disc (CD) or online at TacomaPermits.org. See tip sheet on Electronic File Standards G-230.

 Submittal requirements include plans drawn to scale with adequate information to understand the new construction and/or modifications meeting design requirements and applicable codes for construction and inspection. A clear scope of work also assists.  More information can be found at Accessory Dwelling Unit Help Page  

Permit application and review.

After work is completed, contact PDS to request a new address and schedule necessary inspections.

Example Attached and Detached ADU site plans

 

 

Translate »