Skip to main content
This section is included in your selections.

Accessory Dwelling Unit User Guide

A. Purpose. The purpose of the accessory dwelling unit (ADU) and tiny home provisions is to:

1. Provide a housing type that responds to changing needs and lifestyles (e.g., small families, retired couples) and that allows persons of all ages and incomes to live in a neighborhood by promoting diversity in the size, type, and price of new single-family development;

2. Enhance opportunities for ownership housing;

3. Better utilize existing infrastructure and community resources;

4. Add to Redmond’s stock of affordable dwelling units; and

5. Ensure that ADUs are compatible with surrounding land uses by appropriately regulating their bulk, size and scale.

B. Applicability. The provisions of this section apply to all accessory dwelling units.

C. Requirements.

1. Number of ADUS. One ADU or tiny home shall be allowed on each residential lot as subordinate to any new or existing detached single-family dwelling unit in the City of Redmond.

2. Location.

a. An ADU may be added to or included within the primary unit, or located in a detached structure on the same lot as the primary dwelling unit.

b. Detached ADUs and the primary dwelling unit must each conform to all setback and lot coverage restrictions and any other standards or regulations required of a detached dwelling unit in a residential zone.

c. The maximum height for a detached ADU is 28 feet.

d. Tiny homes located within public view shall provide landscaping to fully screen the tandem axle trailer or similar configuration of trailer base.

3. Size/Scale.

a. The total square footage of an ADU shall not exceed 50 percent of the total square footage of the primary dwelling unit , and in no case shall it exceed 1,500 square feet.

Example: Current home: 2,000 sq. ft.

Primary Dwelling Unit Size


Maximum size


ADU Maximum Size

2,000 sq. ft.


50 percent


1,000 sq. ft.

b. If an ADU occupies an entire single floor of the primary dwelling unit, the Technical Committee may allow for an increase in the allowed size of the ADU in order to efficiently use all of the floor area, so long as all other standards of this section are met.

c. If the site size is larger than 10,000 square feet, the Technical Committee may allow for an increase in the allowed size of the ADU so long as all other standards of this section are met and the following criteria are met:

i. The ADU is an affordable housing unit; or

ii. A public benefit is provided as deemed appropriate by the Technical Committee.

d. A tiny home shall not exceed 400 square feet in size.

4. Subdivision. An ADU shall not be subdivided or otherwise segregated in ownership from the primary dwelling unit.

5. Occupancy.

a. Short-Term Rentals. For short-term rentals and vacation rentals, where the lease term is less than 12 months, the owner must reside at either the primary unit or accessory dwelling unit.

b. Long-Term Rentals. For long-term rentals, where the lease term is 12 months or more, the owner is not required to occupy the site so long as documentation is provided that both the primary and accessory dwelling units are under signed leases for no less than 12 months.

c. A permit authorizing an ADU shall not be issued until the City receives proof of recordation of an instrument requiring compliance with the requirements of this section.

6. Parking. One off-street parking space is required for an ADU in addition to the parking required for the primary dwelling unit. Parking spaces must be paved and may include private driveways, garages, carports, or off-street areas reserved for vehicles.

a. For off-street parking associated with an accessory dwelling unit that is located within one-quarter mile of a major transit stop, refer to RZC 21.40.010.D.4, Parking Near Frequent Transit.

7. Exterior Modification ADUs. Only one entrance on the front of the primary dwelling unit is permitted. Additional entrances are permitted on the side and rear of the primary structure. The Technical Committee may allow both entrances to the primary and accessory units to be located on the front of the structure where design, site layout, and construction considerations significantly hinder other options. Additions to an existing structure or the development of a newly constructed detached ADU shall be designed consistent with the existing facade, siding, and windows of the primary dwelling unit.

8. Home business shall be allowed, subject to existing regulations, in both the ADU and the primary unit.

9. Affordable Requirement. ADUs shall not be used to meet any requirement to provide affordable dwelling units per RZC Chapter 21.20, Affordable Housing.

10. Applicable Codes - ADUs. The portion of the single-family dwelling in which the accessory dwelling unit is proposed must comply with all standards for health and safety contained in all applicable codes, with the exception of the ceiling height requirements of the International Building Code. The Building Official may waive the ceiling height requirements of this chapter if it is determined that the structure was built in compliance with past building code requirements.

D. Cancellation. Cancellation of the ADU approval may be accomplished by the owner recording a document with the King County Department of Public Records and Elections against the title removing the ADU restriction described in subsection C.5 of this section. The cancellation document will confirm that the property has reverted to use as a single dwelling unit and that the former ADU is not to be used as a separate dwelling unit. The property owner shall provide proof of recordation to the Administrator. Cancellation may also occur as a result of an enforcement action. (Ord. 2733; Ord. 3028; Ord. 3083)

Effective on: 7/2/2022