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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.

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.

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.

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.

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.

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.

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.

Seattle ADU setbacks shape where a backyard cottage can go. See the rear and alley rules, side yard numbers, through lot front setbacks, the 5 foot separation from the house, what can project into a setback, how older garages convert and how fire separation distance limits walls and windows near a lot line.

Most Seattle residential lots allow a backyard cottage. Whether yours can fit one comes down to setbacks, coverage, access, utilities, trees, easements and critical areas.