On June 30, 2025, several adopted pieces of legislation became effective in Seattle related to compliance with State laws aimed to boost housing supply and diversify housing options in Seattle’s residential zones. These code changes, put forward by Mayor Harrell and adopted by Council, are known as the HB1337 and… [ Keep reading ]
Substantial alterations are a part of the Seattle Residential Code (SRC) that is applied when a large percentage of the house is being renovated or a large addition is being constructed; SRC Section R107.9. The requirements of substantial alterations are to update the house to the current code for major life safety items of fire, egress, and seismic. Substantial alterations may be required when an attached accessory dwelling unit (AADU) is created as an addition to an existing house. Traditionally, SDCI has given a break from substantial alterations when an AADU is being created in an existing house to support the housing need in Seattle, though this break has not been given when a new addition to a house is for an AADU. Recently, SDCI has revised the policy to allow fire wall construction in compliance with Seattle Building Code 706 to separate a new addition from an existing dwelling unit per SRC 107.5.
To help more residents own and rent accessory dwelling units (ADUs), the City is currently seeking submissions of designs for detached ADUs, often called DADUs or backyard cottages. Pre-approved designs will offer a faster, easier, and more predictable path to permit and construct a DADU. Homeowners choosing a pre-approved plan… [ Keep reading ]
