HomeMy WebLinkAboutPlanning 2018-02-15 ITEM 4 - ACCESSORY DWELLING UNIT (ADU) - INFORMATIONAL MEMORANDUM •
City of Tukwila Allan Ekberg, Ma or
Department of Community Development-.lack Pace, Director
INFORMATIONAL MEMORANDUM
To: Tukwila Planning Commission
From: Nora Gierloff, Deputy DCD Director
Date: January 29, 2018
Subject: L17-0067 Accessory Dwelling Unit Code Amendments
Background
In March 2017 the City Council held a Housing Policy Work Session and considered a variety of housing
related actions. One of the items that the Council prioritized for policy consideration was an update to
Accessory Dwelling Unit (ADU) zoning standards to be followed by an amnesty program for existing
units.The intention was to create additional housing options and address the life safety issues in the
many illegal ADU conversions in the City.
At the October 26, 2017 public hearing the Planning Commission chose from a variety of proposed
policy changes related to Accessory Dwelling Units (ADUs). Staff has prepared a draft of the code
changes in strikeout/underline to codify those policy choices along with other suggested edits.
The City performed an environmental review (SEPA analysis) on this non-project action to amend the
Zoning Code with the proposed ADU changes and issued a Determination of Non-Significance (DNS) on
January 24, 2018.
Discussion
The policy direction set by the PC in October is summarized as follows:
1. Allow detached ADUs under the following conditions:
• Not allowed if there is an attached ADU on site (only 1 ADU per parcel)
• Unit may be up to 1,000 square feet (must still meet the existing standards for total building
footprints of 2,275 sf and maximum impervious area of 4,875 sf for a 6,500 sf lot, see sample
site plans at Attachment B)
• Detached units must be set back at least as far from the street as the main house.This would
not apply to the second front of a through or corner lot, or where the unit is incorporated into
an existing structure such as a detached garage.
Tukwila City Bull • 6200 Southcenter boulevard • Tukwila, WA 98188 • 206-433-1800 » Website:TukwilaWA.gov
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• Limit height to 20 feet except for apartments built over a garage which may be up to 25 feet
tall. Building height is calculated from the mid-point of any elevation change across the
footprint of the house to the mid-point of the pitched roof.
2. Increase the percentage of the house that can be occupied by an attached ADU from 33%to
40% up to a maximum of 1,000 SF, whichever is less.
3. Reduce the lot area requirement from 7,200 square feet to 6,500 square feet for both
attached and detached ADUs.
4. Retain the owner occupancy requirement for 1 unit on site, either the house or ADU.
5. Retain the requirement that ADUs up to 600 SF are required to have 1 off-street parking space
while units over 600 SF are required to have 2 additional spaces. However, allow a waiver of
the second space for ADUs over 600 SF if the ADU is located on a block with on-street parking.
6. Provide a 1-year amnesty period for registration of illegal ADUs and allow owners to request
flexibility from the Director for the following standards:
• Exceeding the permitted height for a detached ADU
• Exceeding the permitted area for an attached or detached ADU
• Not providing a second parking space for an ADU over 600 sf in area, if required
• Roof pitch of less than 5:12
• Location of the ADU on the lot.
Owner occupancy, providing at least 1 parking space per ADU, and meeting the 6,500 SF
minimum lot size would not be waived.
7. Do not create a residential occupancy limit in the Zoning Code but continue to enforce the
International Building Code occupancy load of 200 square feet per person.
Additional Changes
Staff suggests adding a definition of ADU to the Zoning Code for clarity. We currently have definitions
of dwelling unit, single-family dwelling, and multi-family dwelling.This change has been included in the
draft changes at Attachment A.
Currently ADUs are allowed as accessory uses in the following Zoning Districts:
• Low Density Residential,
• Medium Density Residential,
• High Density Residential,
• Office,
• Residential Commercial Center,
• Neighborhood Commercial Center,
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• Regional Commercial,
• Tukwila Valley South, and
• Tukwila South Overlay.
During the environmental review process it was proposed to remove ADUs as an accessory use in the
non-residential districts O, RCC, NCC, RC,TVS and TSO because they must be accessory to an owner-
occupied single-family house. Allowing additional residential uses in these zones would increase
incompatible uses and environmental impacts such as noise. This change has been included in the draft
changes at Attachment A.
Staff suggests that ADUs be limited to rental periods of 30 days or more and be subject to the
Residential Rental Business License requirements.This is consistent with the current standard for
multi-family units and meets the policy goal of creating additional housing options for Tukwila
residents. This change has been included in the draft changes at Attachment A.
Comprehensive Plan Goal 3.2
The City of Tukwila has safe, healthy and affordable homes for all residents in Tukwila.
Policy 3.2.2
Encourage a full range of housing opportunities for all population segments, including very low-income
households earning less than 30%AMI, through actions including, but not limited to, revising the
Tukwila zoning map and development codes as appropriate, which would enable a wide variety of
housing types to be built.
Implementation Strategy
• Following the neighborhood outreach process, consider allowing a detached accessory dwelling
unit in the Low-Density Residential zone on all lots that meet the minimum lot area, when
various appearance and performance criteria related to impacts on adjacent properties are
satisfied.
Recommendation
Forward the proposed code changes with or without amendments to the City Council for adoption.
Attachment
A. Draft ADU Code Changes in Strikeout/Underline
B. Sample Site Plans with Detached ADUs
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