Long-form guides for owners building in the Puget Sound
In-depth guides on ADUs, kitchens, bathrooms, roofing, foundations, permits, and contracts — written by Puget Sound builders, grounded in Washington code and local data.
24 guides · updated continuously
- 9 min read · updated May 2026
Puget Sound ADU timeline guide: kickoff to keys
A jurisdiction-by-jurisdiction breakdown of design, permit, and construction timelines for detached and attached ADUs across Seattle, Bellevue, Kirkland, Redmond, and Tacoma — based on real 2025–2026 SDCI median data.
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- 8 min read · updated May 2026
ADU utility upgrades: sewer, water, and electrical service
The three utility upgrades that quietly add $15K–$50K to an ADU project, how to check capacity before design, and what King/Pierce/Snohomish County actually require in 2026.
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- 8 min read · updated May 2026
DADU vs AADU in Puget Sound: which to build (2026)
Side-by-side comparison of detached ADUs and attached/conversion ADUs in Seattle and the Eastside — cost per sqft, permit time, financing eligibility, resale impact, and the seven scenarios where each wins.
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- 7 min read · updated May 2026
Five hidden ADU costs that wreck Puget Sound budgets
Side-sewer surprises, electrical service upgrades, tree-protection fees, stormwater retention, and arborist/geotech reports — what they actually cost in 2026 and how to surface them at feasibility, not framing.
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- 9 min read · updated May 2026
Seattle ADU financing: 7 loan products compared (2026)
Side-by-side comparison of seven Puget Sound ADU loan products — HELOC, cash-out refi, HomeStyle, CHOICERenovation, FHA 203(k), construction-to-perm, and credit-union ADU lines — with rate, LTV, draw timing, and the situations each one wins.
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- 6 min read · updated May 2026
Seattle MFTE for ADUs: do you qualify? (2026)
Seattle's MFTE program offers a 12-year property tax exemption on residential improvements in qualifying zones — and ADUs can sometimes qualify. This guide breaks down eligibility, income limits, application timing, and the trade-offs.
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- 9 min read · updated May 2026
Foundation inspection checklist for Puget Sound homes
A 14-point foundation inspection covering settlement, water intrusion, crawlspace condition, and seismic readiness — what's normal, what's actionable, and what's a deal-breaker.
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- 9 min read · updated May 2026
Pacific Northwest foundation types: slab, crawl, pier, basement (2026)
Slab-on-grade, crawl space, pier-and-beam, and full basement — how soil, slope, seismic zone D2, and groundwater drive foundation choice in Seattle and the Eastside. Cost, R-value, longevity, and the failure modes each type is prone to.
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- 6 min read · updated May 2026
Crawlspace vapor barriers in the Puget Sound (2026)
Puget Sound crawlspaces collect moisture year-round. This guide breaks down vapor barrier thickness, ground cover overlap, vent strategy, conditioned vs. vented assemblies, and the WSEC 2021 requirements that apply on ADUs and remodels.
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- 11 min read · updated May 2026
Seattle SDCI ADU permit process, step by step (2026)
Every form, drawing, and reviewer interaction in the SDCI Type II ADU permit, from intake through issuance. Median 12–16 weeks; 4–6 weeks via Pre-Approved DADU.
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- 8 min read · updated May 2026
King County side sewer permits for ADUs: cost & timeline (2026)
Side sewer is the #1 hidden cost on Puget Sound ADU projects. This guide breaks down SPU side sewer permits, King County Capacity Charge, repair vs new tap, slope requirements, and the median fees and timelines for 2025–2026.
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- 8 min read · updated May 2026
ADU stormwater & detention requirements in Puget Sound (2026)
Stormwater is the second most expensive surprise on Puget Sound ADU projects. This guide covers SMC 22.800–22.808, King County Surface Water Design Manual, when detention is required, low-impact development options, and 2025–2026 cost ranges.
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- 6 min read · updated May 2026
Seattle Design Review for ADUs: when it applies (2026)
Seattle Design Review can add 6–12 months to a project. This guide explains when DR applies to ADUs, the streamlined Administrative DR path, Early Design Guidance meetings, and how to scope a project to stay under thresholds.
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- 6 min read · updated May 2026
Puget Sound view corridor & height restrictions on ADUs (2026)
Mercer Island, Medina, Hunts Point, and Seattle's territorial-view neighborhoods enforce strict view-impact rules that constrain ADU height and placement. This guide explains the rules and the design moves that satisfy them.
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- 7 min read · updated May 2026
Fixed-price vs time-and-materials: which contract to sign
How fixed-price and T&M (cost-plus) contracts actually allocate risk on Puget Sound construction projects — and the seven scope situations where each is the honest choice.
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- 7 min read · updated May 2026
Seattle electrical panel upgrade for ADUs: 100A to 400A (2026)
When does your ADU need a service upgrade? Walk-through of Seattle City Light and PSE service upgrade requirements, load calcs, panel sizing, EV-ready code, and 2025–2026 cost ranges for 100A, 200A, and 400A services.
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- 8 min read · updated May 2026
ADU rental management in the Puget Sound (2026)
From RRIO registration in Seattle to King County deposit limits, this guide covers the operational and legal pieces of renting an ADU: long-term vs. short-term rules, screening, lease clauses, insurance, and the 2026 tax picture.
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