Issaquah Hillside DADU
Two-story DADU on a 22% sloped lot in Issaquah Highlands — engineered piers, cable-rail deck, panoramic Lake Sammamish view.
- Type
- Detached ADU
- Sqft
- 950
- Beds / Baths
- 2 / 1
- Completed
- Nov 2024
- Duration
- 38 wks
- Budget
- $332,000
01 / BRIEF
What the owner asked for
Owners wanted to capture lake views from a buildable backyard envelope on a heavily sloped Issaquah Highlands lot. IMC 18.07 requires geotech review for any structure on slopes >15%.
02 / CHALLENGE
What stood in the way
Slope, view corridors restricted by HOA CC&Rs, and a 30-foot stream buffer running along the south edge of the lot.
03 / APPROACH
How we solved it
Helical pier foundation (Magnum MH150, 9 piers) eliminated cut/fill and protected the stream buffer. Building was rotated 14° off the property line to align with view corridor while staying within HOA envelope.
04 / OUTCOME
What got delivered
Permit in 16 weeks (geotech + critical areas review), build in 22 weeks. Owners' parents moved in for winter 2024–25.
SPEC_05 / FACTS
Project specification
- Footprint
- 475 sqft (two-story)
- Bedrooms / baths
- 2 / 1
- Foundation
- 9 helical piers, Magnum MH150
SCHEDULE_06 / PHASES
38-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 review16 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, 22-week build closeout.
MATERIAL_07
Materials
- CladdingKebony pine rainscreen, 1x6 horizontal
- Deck railAGS Stainless Clearview cable rail
SYSTEM_08
Systems
- Heating / coolingDaikin Aurora 18K BTU multi-zone hyper-heat
PERMIT_09 / RECORD
Permits & compliance
- Permit numberIssaquah B24-0455
- GeotechEarth Solutions NW report ESNW-24-119
- Critical AreasStream buffer mitigation plan approved
METRIC_10 / OUTCOME
By the numbers
- 9
- Helical piers
- 0 cu yd
- Cut/fill
LESSON_11 / FIELD NOTES
What we'd repeat
- Helical piers cost ~$28K more than a conventional foundation but on >20% slopes they often save 4–6 weeks of excavation and shoring.
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 "Issaquah Hillside DADU"?
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 "Issaquah Hillside DADU" 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 "Issaquah Hillside DADU" 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 "Issaquah Hillside DADU" 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