HomeMy WebLinkAboutPCD 2024-05-13 Item 1A - Discussion - Housekeeping Amendments to Accessory Dwelling Units (ADUs) Standards
City of Tukwila
ThomasMcLeod, Mayor
INFORMATIONAL MEMORANDUM
TO:Planning and Community Development
FROM:Nora Gierloff, DCD Director
BY:Isaac Gloor, Associate Planner
CC:ThomasMcLeod
DATE:May 13, 2024
SUBJECT:Title 18 Housekeeping: Accessory Dwelling Units
ISSUE
Minor housekeeping amendments to Title 18 to updateAccessory Dwelling Unit development
standards.
BACKGROUND
In November of 2023, the City Council approved zoning code amendments that altered the
development standards for Accessory Dwelling Units (ADUs) to comply with the recently passed
State Law, known during development as HB 1337. These amendments allow for all parcels
where Single-Family Homes are permittedto now develop up to two ADUs, in either attached or
detached form, without owner occupancy and, if near frequent transit,without additional parking.
Parking standards for single-family homes were not changed, and ADUs are still subject to most
of the samedevelopment standards assingle-family homes are, including setbacks and
impervious surface limits.While the majority of the changes made were amendments to TMC
since the
DISCUSSION
Below is a summary of the identified code sectionsand proposed changes:
TMCTable 18-6:Land Uses Allowed byDistrict
o Issue:State law requires that Tukwila permit ADUs anywhere that the City
permits Single--Family Homes are
districts: Low-Density
Residential, Medium-Density Residential, and High-Density Residential. The land
use table currently permits ADUs within those districts. However, Tukwila also
permits single-family homes within several other districts, including the Mixed
Use Office(MUO), Office(O), Residential Commercial Center(RCC), and
Neighborhood Commercial Center(NCC)districts. As Table 18-6 does not show
that ADUs are permitted within those districts, Tukwila could not allow a new
ADU to be established within them. This leaves Tukwila out of compliance with
the requirements of State Law.
o Suggested Change:Staff proposes to amend TMC Table 18-6 to include ADUs
as permitted accessory uses within the MUO, O, RCC, and NCC zoning districts.
While this would permit ADUs within 4 additional zoning districts than what is
currently permitted, the impact is expected to be minor, as these districts do not
currently contain many eligible properties and are unlikely to in the future.
TMC 18.50.220(B)(3):Accessory Dwelling Unit (ADU) Standards; General Standards
o Issue: This code section establishes the maximum size of detached ADUs,
which, as required by the State, is set at 1000 square feet. However, it also
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INFORMATIONAL MEMO
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states that if an ADU is built over a detached garage, the department will not
count the square footage of the detached garage toward the maximum size of an
ADU. While this is accurate, it implies that in other scenarios, the department
wouldcount the square footage of a garage and use that to limit the size of
ADUs. This implicit meaning is unintentional, and if enforced, would violate state
requirements.
o Suggested Change:Staff proposes to amend TMC 18.50.220(B)(3) to remove
If built over a detached garage, the detached garage would not
This change would remove the
implication that other types of garages may count toward ADU area limits. This
sentence is unnecessary, as garages are not habitable and would not count
toward an ADUs floor area in any circumstance.
TMC 18.50.055(C):Single-Family Dwelling Design Standard Exceptions
o Issue:Washington State allows cities to establish design standards for ADUs,
provided that those standards are no more restrictive than the standards for
single-family dwellings. The TMC does this by establishingdesign standards for
all new single-family dwellings, as well as accessory dwellingunits and other
accessory structures that require a building permit. These standards, as they are
equally applied, comply with State requirements. Prior to the November code
Dwelling Unit standards contained
design requirements that were more restrictive than those for single-family
homes. While those requirements were removed from the code specifically
-family design standards still contain a
reference to the now defunct code section.
o Suggested Change:Staff proposes to correct this scriveners error and remove
TMC 18.50.055(C).
FINANCIAL IMPACT
None.
RECOMMENDATION
The Committee is being asked to forwardthis issue to the Planning Commission for a
recommendation. It will then be returned to Council in ordinance form for a hearing and
decision.
ATTACHMENTS
None.
https://tukwilawa.sharepoint.com/sites/departmentofcommunitydevelopment/DCDPlanning/Current Planning/ISAAC - projects/Zoning Code
Amendments/2024/ADU Housekeeping/PCD Info Memo - ADU Housekeeping.docx
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