Seattle DADU Guides & Real Estate Notes
Everything Bob writes, in two places: the DADU feasibility guides, and broader notes on Seattle property and homeownership.
Every guide is written against Seattle’s code, for a parcel inside the city limits. Want your own area instead? The 18 measured neighborhood profiles put these rules against real lot sizes, slope and tree canopy, and the service-area page says plainly where the coverage stops.
Seattle DADU & ADU Guides
Practical guides for Seattle homeowners evaluating DADU and ADU feasibility. Updated for 2026 law.
Seattle DADU Permits in 2026: Process, Timeline, Fees, and the Pre-Approved Shortcut
Seattle DADU permits in 2026: the step-by-step process, a measured 138-day citywide median, SDCI's published 2–6 week pre-approved path, and the fee stack — all sourced.
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Seattle Pre-Approved DADU Plans: Which Ones Actually Fit Your Lot (2026)
Which pre-approved DADU plan fits my lot is the question the City's gallery can't answer for you. Here's how to measure your buildable rectangle, read the plans by footprint, and screen the site conditions that quietly remove the fast permit path.
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Seattle Pre-Approved vs Custom DADU: The Real Permit Cost and Timeline Gap
Pre-approved vs custom DADU: the permit timeline gap is real (2–6 weeks against a 138-day citywide median), but the fee savings are in design, not in the SDCI schedule. A retired builder lays out the true cost and time difference.
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HB 1110 on Your Lot: How Many Units Can You Actually Build in Seattle?
HB 1110 says four units on a Seattle lot, six near transit. The number you can actually build depends on your lot size, transit walkshed, coverage, and trees. Here's the density math, worked on real Seattle lots.
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Seattle DADU vs Fourplex: What Your Lot Is Really Zoned to Earn
One DADU or four units? Seattle's NR zoning now allows both. Compare the build cost, rent, fees, and taxes that decide whether a cottage or a fourplex actually pays on your lot.
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Seattle Tree Removal Permit Rules for a DADU: Process, Fees, and When You Need an Arborist
Which Seattle trees can block a DADU, when you need a tree removal permit, what SDCI charges by request type, and what an arborist report costs — the permit process fact-checked, not just the tiers.
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Seattle Critical Areas: When ECA Review Kills the Fast DADU Permit
Seattle environmentally critical areas (ECAs), explained for DADU builders: the ten designations, when they trigger geotech, the buffers that move a cottage, and the neighborhoods with the worst ground.
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Seattle DADU Cost in 2026: A Builder's Line-by-Line Budget
A Seattle DADU costs $400–$650 per square foot turnkey, of which $420–$616 is design and build, before your lot has a say. A retired builder prices a real 1,000 sq ft cottage line by line — hard costs, soft costs, city and county fees, and the hidden items that reset budgets.
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Seattle DADU Setback Requirements (2026): Front, Side, Rear, Alley
Seattle DADU setback requirements: 15 ft front, 5 ft side (3 ft minimum), 5 ft rear or 0 ft at an alley, 5 ft separation, 50% coverage, 32 ft height, 1,000/1,200 sq ft. Three worked examples drawn to scale.
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Seattle's Tree Ordinance and Your DADU: How Tier 2 Trees Decide Where a Cottage Can Go
SMC 25.11 tiers every Seattle tree by trunk size, and Tier 2 trees (24 inches or more) are the ones that decide where a DADU fits. Tiers, root protection areas, the Registered Tree Service Provider rule, fines, and SDOT street tree permits — fact-checked.
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Seattle Pre-Approved DADU Standard Plans That Can Save You Weeks on Permitting
Pre-approved doesn't mean pre-feasible. Here's the complete fact-checked guide to Seattle's standard DADU plans, lot eligibility, permit timelines, and the site risks that still matter.
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Can I Build a Backyard Cottage in Seattle? The 2026 Requirements
Can I build a backyard cottage in Seattle? The 2026 requirements and regulations, by code section: 15 ft front, 5 ft side, 5 ft rear, 50% coverage, 32 ft height, 1,000/1,200 sq ft, two ADUs, no parking — plus the 7 things that actually decide.
Read the guide →Seattle Real Estate Notes
Broader notes on Seattle property, homeownership, and the local market — written from years on Seattle job sites.
Seattle Property Records: How to Read Your House's Paper Trail
Who owned it, when it was really built, what was permitted and what quietly wasn't, and what is buried in the yard — the free Seattle and King County sources for your house's paper trail, and the limits of each one.
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King County Property Tax Appeal: The 60-Day Deadline, Comps, and a DIY Evidence Packet
The King County property tax appeal deadline is 60 days from your notice — not July 1. Here's what the Board considers, which comps win, and how to assemble the evidence packet.
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Why Your Seattle Tax Bill Went Up When Values Went Down (and What to Do)
Seattle property tax went up while values fell? Here's the levy-rate mechanics behind it, why it happens every cycle, and the 60-day appeal window that is your only real lever.
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Seattle DADU Rental Income in 2026: Real Numbers, Fees, and Taxes
Seattle DADU rental income, priced net of fees and taxes: real 2026 rent data, the King County capacity charge, SPU drainage, and a worked 15-year cash-flow example on a 2-bedroom cottage.
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Seattle DADU ROI: The Payback Math, Year by Year (2026)
Seattle DADU ROI, year by year: the $414,500 typical build, $2,700 rent, the $17,759 first-year net, payback about year 17 on cash, and what a 7.25% HELOC does to the return.
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Seattle Housing Market September 2026: Prices Flat, Rents Holding, Rates Above 6.5%
Seattle home prices went flat in September 2026 — down 1.6% year over year — while rents kept climbing and mortgage rates held above 6.5%. Here's what that means if you own a Seattle lot.
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Seattle DADU Property Tax: What a Backyard Cottage Does to Your Bill, Rent Roll and Resale
How a Seattle DADU is taxed, when the Assessor picks up the new value, what it rents for, and the state law that lets you sell the cottage separately.
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Seattle's Alley Lots: The Quiet Advantage 1920s Platting Gave Some Neighborhoods
Seattle's 1920s platting left some neighborhoods with a public alley behind every lot — and others without. That one difference changes the setback, the utility run, and what a DADU costs to build.
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Get your feasibility report — $149
Your address run through every factor — zoning, setbacks, trees, critical areas, utilities, and a permit path — measured from City records and reviewed by a person. Prefer to self-study? The Pro Guide covers the same rules in depth.