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DADU contract pricing shapes who carries cost risk on a backyard cottage. Topics include fixed price and cost plus contracts, fee types, allowances, hidden site conditions, Washington sales tax rules, required contract terms, the RCW 18.27.114 disclosure, payments by phase, retainage, lien releases, cost records, markup, change orders and questions to ask before signing.

Seattle ADU permit fees for a backyard cottage follow a set formula in the SDCI Fee Subtitle. Topics include how the city values a DADU, the 2026 fee index math, the 18 percent increase, hourly and correction charges, electrical permits, payment timing, standard plans, fee year rules, refunds and charges from other agencies.

A DADU contingency budget holds money for necessary work nobody can price at signing. Topics include the difference from allowances, Seattle side sewer ownership and repair permit fees, tree protection, SDCI hourly and reinspection fees, special inspections, permit revisions, sizing the reserve, approving and tracking draws and lien precautions.

DADU finish allowances hold the price range for interior items that are still unpicked when a contract is signed. This covers which selections carry allowances, what each line should spell out, Washington contract guidance, change orders, Seattle energy code lighting rules, appliance and water heater credits, fixture flow limits and when to lock in choices.

Two Seattle backyard cottages of the same size can cost very different amounts to build. This covers how footprint shape, roof form, stories, glass and ceilings drive DADU design cost, plus lot coverage, stormwater triggers, permit valuation and pre-approved plan limits, with an invented comparison and questions to settle before drawings.

A Seattle backyard cottage can trigger published utility charges on top of trenching. This covers who bills what, when a DADU needs a larger water service, 2026 SPU installation and system development charges, side sewer permits, the King County capacity charge at the ADU rate, drainage charges, City Light service steps, lead times and an invented example.

Site work for a Seattle backyard cottage grows with the city thresholds the ground triggers. This covers grading limits, walls near property lines, the pre-application site visit, stormwater review at 750 square feet, tree protection areas, critical areas and the dry season, utility locates and old heating oil tanks, with an invented example.

A backyard cottage estimate is a list of scope decisions, and two similar totals can describe very different projects. This walks through design, permits and county charges, site staging, building systems, utilities, allowances, general conditions, sales tax, contingency and exclusions, with questions to ask every bidder.

The same backyard cottage plan can carry very different budgets on two Seattle lots. This walks through slope and access, utility runs and King County charges, standards that do not apply to ADUs, design shape, pre-approved plans, labor and finish allowances, with a checklist before asking for estimates.