archive blog
What Happens During Seattle DADU Plan Review?
A Seattle DADU review sends one plan set through several code checks at SDCI. Learn how a project reaches intake and which drawings Tip 116B requires. See what land use, building, structural, energy and stormwater reviewers look for, which life safety items must appear and how corrections, fees and permit issuance work.
Which Permits Does a Seattle DADU Require?
DADU permit requirements in Seattle start with one main SDCI construction permit. Learn which trade permits and utility steps usually follow, when environmentally critical areas or trees add reviews, how inspections work after issuance and who handles each approval, including Tip 116B and the SDCI ADU pages.
How Seattle Middle Housing Changes Affect ADU Planning
Seattle middle housing rules took effect January 21, 2026, and let many Neighborhood Residential lots hold four or more homes. Learn how the density options, the two ADU limit, floor area, height, setbacks and parking work, why an ADU cannot be split off through subdivision and when a single backyard cottage is still the simpler path.
When Protected Trees Affect DADU Placement
Seattle DADU trees often decide where a backyard cottage can sit. Learn how Seattle sorts trees into tiers, how a tree protection area is measured and adjusted, when a Tier 2 tree may be removed on a Neighborhood Residential lot, how retained trees can raise the height limit and what to check with an arborist and SDCI before design starts.
How Easements Can Limit DADU Placement
DADU easement restrictions can rule out a cottage site that meets every zoning rule. Learn what an easement is under Washington law, why recording matters, how to find recorded documents in King County, what SDCI Tip 103 requires on the site plan and how new utility lines can add new easements.
What Parking Rules Mean for Seattle ADU Projects
Seattle ADU parking is optional because SMC 23.42.022 requires no off street space for an accessory dwelling unit. See how state law caps parking rules, where a voluntary space can go, why alley access comes first and what curb cuts, EV ready circuits, stormwater review and Restricted Parking Zones add.
Can a Seattle Property Have Two Accessory Dwellings?
Two ADUs Seattle code allows on one lot can be attached, detached or stacked under SMC 23.42.022. Both count toward density, share the 50 percent lot coverage and FAR limits and need their own permits. Two attached units in an existing house can trigger a different building code review, so check early.
How Seattle ADU Size Rules Affect Bedroom Choices
Seattle ADU size caps sit at 1,000 square feet of gross floor area for units with up to two bedrooms and 1,200 for three or more. See what garage, underground and bike parking space is left out, how conversions work and how state law sets a 1,000 square foot floor.
What Lot Coverage Means for a New Backyard Home
Seattle lot coverage in Neighborhood Residential zones is capped at 50 percent, and a backyard cottage counts toward it. See which eaves, decks and porches are left out, how critical areas shrink the countable lot, when 60 percent applies, how FAR works alongside coverage and how older garage conversions are treated.
How Height Limits Shape Backyard Cottage Design
DADU height limits in Seattle Neighborhood Residential zones start at 32 feet. See how a pitched roof adds up to 5 feet, when a retained tree raises the base to 42 feet, how average grade is measured, what rooftop features may extend higher and how the 12 foot setback rule and state law fit in.