Backyard Cottage contractor —
Seattle & Puget Sound.
A backyard cottage is a DADU with a residential vocabulary — gabled rooflines, lap siding, traditional trim. Same engineering, more neighborly silhouette.
A backyard cottage is a DADU dressed in a residential vocabulary — gabled rooflines, lap siding, traditional trim — that reads as a small house instead of a modern accessory box. The engineering is identical to a contemporary DADU; the architectural restraint is what changes.
We build backyard cottages across Seattle, Bellevue, Kirkland, Redmond and the Eastside under WA HB 1337 and city DADU rules. Most owners choose this style when the primary residence is a craftsman, Tudor, or traditional and a flat-roofed modern would look transplanted.
What we build
SCOPE- 01Pitched roof + dormer detailing
- 02Lap siding + traditional trim
- 03Covered porch / entry
- 04Income-ready kitchen + bath
- 05Owner-occupancy compliance
- 06Quiet HVAC + insulation
Phased process
PROCESS- 01
Feasibility & zoning
Confirm lot is eligible for a DADU under the local AHJ. Diagram the buildable envelope after setbacks, lot coverage, and tree-protection zones.
- 02
Architectural design
Match rooflines, trim profiles, and siding rhythm to the primary residence. SDCI / planning intake to confirm height and FAR before drawings finalize.
- 03
Permit submittal
Stamped structural + MEP, energy code compliance forms (WSEC 2021), and stormwater intake. Seattle DADU pre-approved track when eligible.
- 04
Site & foundation
Tree protection, utility locates, excavation, stem-wall foundation or pier-and-beam where soils require.
- 05
Framing & envelope
Conventional stick framing, advanced air sealing, continuous exterior insulation, and rain-screen siding assembly.
- 06
MEP & finishes
Independent electrical sub-panel, mini-split or heat-pump HVAC, hard-wired smoke/CO, and the finish carpentry that makes the cottage read residential.
- 07
Inspection & handover
Final SDCI / building inspection, blower-door test, address assignment, and warranty package.
Spec sheet
SPEC- +Pitched gable or hip roof, 30-yr architectural composition shingle or standing-seam metal
- +James Hardie or cedar lap siding with traditional 4–6" exposure
- +Marvin or Pella double-hung / casement windows with painted casing
- +Covered front entry porch with engineered post + beam
- +ENERGY STAR mini-split heat pump (ductless or short-duct)
- +Independent 100A electrical sub-panel and meter base
- +Hard-wired smoke/CO + dedicated egress windows per IRC R310
Cost drivers
COST- Sloped or rocky lot+$15K–$60K for engineered foundation, retaining, and excavation
- Long utility runs (>50 ft)+$8K–$25K for trenching, conduit, and side-sewer extension
- Tree protection ordinance+$3K–$10K for arborist letters and protection fencing
- Two-story vs single-story+$25K–$60K total; usually offsets via smaller footprint
- Finish level (rental vs owner-occupied)±$40K depending on cabinetry, tile, and fixtures
Codes & permits
COMPLIANCE- WA HB 1337 (2024)
Removed owner-occupancy requirement statewide. Both primary home and DADU can be rented as long-term rentals in compliant cities.
- Seattle SDCI Tip 116
Defines DADU height, lot coverage, and pre-approved plan eligibility. Most NR1/NR2/NR3 lots qualify.
- WSEC 2021 (residential)
Requires continuous exterior insulation, advanced air sealing, and blower-door verification under 4.0 ACH50.
- King County Capacity Charge
New DADUs on King County sewer trigger a monthly Capacity Charge for 15 years. Budget at permit submittal.
Is backyard cottage the right call?
- →Primary home is a craftsman, Tudor, or traditional and a modern DADU would clash
- →Targeting long-term rental income with a 'house-like' product
- →Multi-generational housing where the cottage reads as a small home
- →Neighborhood design review or HOA expects traditional forms
Cottage questions
FAQQ.01
Is a backyard cottage the same as a DADU?
Legally yes — a backyard cottage IS a detached ADU. The difference is purely architectural: traditional roofline, siding, and trim instead of a modern flat-roofed envelope. Permits, zoning, and code requirements are identical.Q.02
How big can a backyard cottage be in Seattle?
Same as any DADU: up to 1,000 sq ft of gross floor area under current SDCI rules, with height limited by zone (typically 18–24 ft depending on roof form and lot).Q.03
Does a cottage cost more than a modern DADU?
Usually $10K–$30K more. Pitched roofs cost more than flat, lap siding takes longer than panel siding, and trim work adds finish-carpentry hours. Most owners find the resale and rental premium worth it on traditional lots.Q.04
Can I rent the cottage on Airbnb?
Short-term rental rules vary by city. Seattle requires an STR license and limits operators to two units (primary + one). Bellevue, Kirkland, and Redmond have stricter caps. We confirm during feasibility before you commit.
Official resources & sources
- Source ↗Seattle Pre-Approved DADU Plans
- Source ↗WSEC 2021 Residential Energy CodeEnvelope, HVAC, hot-water and air-sealing requirements
- Source ↗WA HB 1110 — Middle housing lawStatewide middle-housing zoning preemption
- Source ↗WA HB 1337 — ADU statewide rulesTwo-ADU baseline, no owner occupancy, parking limits
- Source ↗WA Dept. of Commerce — ADU resources
- Source ↗WA L&I contractor license lookupVerify Golden State ADU Builders Inc · GOLDESA747LZ
- Source ↗Washington State Building Code CouncilStatewide adopted codes (IRC, IBC, WSEC)
Ready to scope your cottage project?
Send a paragraph and the address. A licensed PM replies within one business day with next steps.
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