Bothell Courtyard AADU
Courtyard-form AADU wrapped around an existing 1985 split-level — Canyon Park, Bothell.
- Type
- Attached ADU
- Sqft
- 680
- Beds / Baths
- 1 / 1
- Completed
- Dec 2024
- Duration
- 26 wks
- Budget
- $238,000
01 / BRIEF
What the owner asked for
Owners wanted a fully private AADU with its own outdoor space. Designed as a U-shaped wing around a 220 sqft gravel courtyard with a single Korean hornbeam.
02 / CHALLENGE
What stood in the way
Bothell's stormwater code (BMC 18.04) required infiltration testing — the lot tested at 0.3 in/hr (Type-C soil), too slow for standard trenches.
03 / APPROACH
How we solved it
Specified a sized infiltration BMP using a 12" amended planting medium per Ecology's 2019 SWMMWW spec.
04 / OUTCOME
What got delivered
Permit in 10 weeks, build in 16 weeks. Owners' college-age daughter moved in for senior year.
SPEC_05 / FACTS
Project specification
- Footprint
- 680 sqft single-story
- Courtyard
- 220 sqft enclosed gravel + hornbeam
SCHEDULE_06 / PHASES
26-week delivery
- 01Feasibility & design4–6 wks
Site survey, zoning memo, schematic plans, owner review.
- 02Construction docs3–4 wks
Structural, MEP, energy compliance, permit-ready set.
- 03Permit review10 wks
City corrections, utility sign-offs, building permit issued.
- 04Site work + foundation3–4 wks
Erosion control, excavation, footings, slab or stem wall.
- 05Framing + dry-in5–6 wks
Floor, walls, roof, windows, weather-resistive barrier.
- 06MEP rough-in + insulation4–5 wks
Plumbing, electrical, HVAC, blower-door prep.
- 07Finish + cabinetry6–8 wks
Drywall, paint, flooring, cabinets, tile, fixtures.
- 08Inspections + handover1–2 wks
Final inspections, punch-list, 16-week build closeout.
MATERIAL_07
Materials
- CladdingVertical Hardie panel + 1x4 cedar batten
SYSTEM_08
Systems
- Heating / coolingBosch IDS Light 12K BTU mini-split
PERMIT_09 / RECORD
Permits & compliance
- Permit numberBothell B-24-1099
METRIC_10 / OUTCOME
By the numbers
- 0.3 in/hr
- Infiltration rate (tested)
LESSON_11 / FIELD NOTES
What we'd repeat
- On Type-C soils, designing the stormwater BMP before the building footprint avoids reshaping the floor plan late.
ARCHIVE_∞ / MORE
Other field reports
- REF_4492 · Detached ADUBallard Monolith
A 1,000 sqft two-story DADU clad in vertical western red cedar with floor-to-ceiling industrial glazing — long-term rental on a 4,800 sqft Ballard lot.
- REF_4376 · Attached ADUBellevue Wing
A 720 sqft side-yard AADU grafted onto a 1962 craftsman in West Bellevue — independent entry, separate utilities, no shared interior wall openings.
- REF_4218 · Garage ConversionKirkland Garage Studio
A two-car detached garage converted into a high-end work-from-home studio with a 6'x6' fixed skylight — Kirkland's Norkirk neighborhood.
Frequently asked
Can I tour a project like "Bothell Courtyard AADU"?
Yes — we typically have 6–10 ADUs in framing or finish at any time across the Puget Sound, so we can usually arrange a site walk on a project at the same stage you're planning. For completed projects, tours depend on the current owner's availability and privacy preferences. Request a tour and we'll match you to the closest active or completed project that resembles "Bothell Courtyard AADU" in size, configuration, and AHJ.
What did this project actually cost?
Each project page includes the all-in cost range for the size and configuration shown, scaled to 2026 prices. Actual contract value at time of build is confidential to the client, but the range we publish is anchored in real numbers from our bid archive — not aspirational pricing. For a tailored estimate against your lot, run our feasibility study or use the cost calculator.
Go deeper: Read the Five hidden ADU costs that wreck Puget Sound budgets guide
How long did this project take?
Most projects of this size and configuration run 9–14 months from contract to certificate of occupancy: 6–8 weeks of design, 8–16 weeks of permit, 18–26 weeks of construction. Schedule variance is driven by AHJ workload, owner selection pace, and field-discovered conditions during demo or excavation. We publish a Gantt at contract and update it weekly.
Go deeper: Read the Eastside deck cost & permits: cedar, IPE, composite (2026) guide
Could you build "Bothell Courtyard AADU" again on my lot?
Often yes — most of our projects are anchored on repeatable design DNA (envelope details, structural assemblies, MEP standard layouts) that adapt to different lot conditions with modest configuration changes. We'll review your lot's zoning, soils, and access to confirm fit. Where the original layout doesn't fit, we propose the closest workable adaptation that preserves the look you liked.
What inspections did "Bothell Courtyard AADU" go through?
Standard Puget Sound ADU inspection sequence applied: footing, underfloor MEP, framing, plumbing rough, electrical rough, mechanical rough, insulation, drywall nailing, shower pan, gas piping, final building, final plumbing, final electrical, final mechanical, and final energy verification (blower-door ≤3 ACH50). All passed with no notable callbacks — typical for our builds because we run internal QA checklists at each milestone.
INTERNAL_LINKS / Deep Map