Seattle's Pre-Approved DADU plans — when they make sense
A free SDCI program that cuts permit time in half. Here's when to use it and when to walk away.
What the program is
SDCI maintains a library of pre-reviewed DADU plan sets from selected architects. Building from a pre-approved set lets the project skip the architectural plan review portion of permitting — typically 6–8 weeks of total timeline savings — and lowers permit fees by removing the hourly architectural review charges.
The program is free to use and the catalog is published on the SDCI website.
When it works
Rectangular lot with no critical-areas overlay. Standard utility access. Straightforward sitework. Owner is comfortable with one of the published designs and not married to a custom architectural expression.
On those lots, pre-approved plans deliver a fully-permitted, livable DADU at 10–15% lower total cost than a one-off custom design.
When it doesn't
Steep grade. Tree protection that constrains the footprint. Unusual lot geometry. Owner wants 1,000 sq ft when the catalog tops out at 800. Fire access constraints requiring a specific footprint orientation.
On those lots, the savings evaporate in modifications — and at a certain modification threshold the plans lose their pre-approval status entirely.
