Engineered carpentry for Seattle’s steep, sensitive, and waterfront parcels.
A meaningful share of Greater Seattle’s most desirable parcels sit on terrain that disqualifies a conventional deck builder. Slopes above thirty percent demand engineered foundations. Environmentally Critical Area overlays demand a permit before the first post hole. Properties within two hundred feet of the Ordinary High Water Mark fall under the Washington Shoreline Master Program. Washington State requires forty-two inch guards and a sixty pounds-per-square-foot live load, both stricter than the International Residential Code baseline. Combined, these constraints describe a class of projects most builders avoid, decline to permit, or quietly build without one.
Our practice is built around exactly this class of work. We operate as a structural and municipal navigator: structural in the sense that our drawings carry stamped Professional Engineer calculations and our foundations reach stable glacial till; municipal in the sense that we file the permit in the homeowner’s name, share the SDCI or jurisdiction tracking number on day one, and absorb the geotechnical review process so the homeowner doesn’t inherit a paperwork backlog at handoff. The goal isn’t a deck that survives the inspection. It’s a deck that survives the slope, the soil, the rain, and the resale.
Anything over a ten percent grade is no longer a flat-lot deck and starts to drive structural decisions on post lengths and lateral bracing. Above thirty percent grade is our standard threshold for engineered footings rather than poured concrete pads. Above forty percent grade in the City of Seattle, the parcel falls inside the SDCI Environmentally Critical Area steep-slope designation by definition, which triggers a separate review pathway.
ECA is a Seattle SDCI overlay that includes steep slopes greater than forty percent, landslide-prone areas, liquefaction zones, peat element zones, flood-prone areas, wetlands, and riparian corridors. Any deck inside an ECA requires a construction permit, regardless of height above grade — the eighteen-inch threshold that exempts low decks elsewhere in Seattle does not apply. Steep-slope ECA further requires a geotechnical hazard review and stamped drawings from a licensed Professional Engineer. Other jurisdictions in the MSA carry analogous overlays; the substance is the same even when the label differs.
Construction within two hundred feet of the Ordinary High Water Mark activates the Washington Shoreline Master Program, administered locally with jurisdiction-specific envelopes. Mercer Island enforces a twenty-five foot landward setback from the OHWM; Medina restricts envelope changes that affect the fire-rated assembly; over-water dock decking must allow at least sixty percent grated open area for light penetration. A waterfront deck is a permitting conversation before it is a carpentry conversation.
Five sequential stages, every one of them documented in the permit file.
Topographic walk of the parcel with grade measurement, ECA overlay verification through Seattle SDCI GIS or the equivalent jurisdiction layer, and a first-pass call on what the foundation system will need to be. We also locate the Ordinary High Water Mark on shoreline parcels and confirm the 200-foot Shoreline Master Program trigger.
Slopes greater than 40% in Seattle SDCI ECA territory trigger mandatory geotechnical review with stamped drawings. We coordinate the soil report, the structural calculations, and the response letters that the reviewer will ask for. Our geotechnical partner is named at quote stage so the homeowner knows who is signing the calcs before the contract is signed.
Washington State requires residential deck framing engineered for a 60 pounds-per-square-foot live load, higher than the IRC baseline. We design ledger attachments, beam spans, post connections, and guard load paths to 2021 IRC Section R507.10 with the WA-specific 42-inch guard height. No notched 4x4 guard posts at the connection point. Continuous load path from rail to footing, documented in the permit set.
Per Washington law, the contractor pulls the permit in the homeowner's name. We file with Seattle SDCI, City of Bellevue, or the applicable jurisdiction and share the tracking number on day one. Standard SDCI ECA reviews run 10 to 17 weeks; we account for that in the construction schedule and flag dependencies before they become delays.
On most slope and ECA parcels we install helical steel piers or Diamond Pier pin-pile foundations. Both reach past the creeping topsoil layer into glacial till without excavation. Concrete footings are used selectively on flatter ECA buffer parcels where ground disturbance is acceptable to the reviewer. Materials and connections meet the substructure spec we engineered, not what's cheapest on the truck.
We treat foundation selection as the most consequential structural decision on any slope or ECA project. Read our journal essay on helical pier engineering for a long-form treatment of glacial till geology, root-zone preservation, and the SDCI ECA review pathway.
Hillside and shoreline parcels share an environmental envelope — persistent rain, marine air, freeze-thaw cycles, and limited drying sun — that punishes wood-flour composites and ages softwoods rapidly. We specify three categories of board where the warranty math, dimensional stability, and supply-chain ethics all align.
Solid-PVC core with a co-extruded cap. Moisture-immune, dimensionally stable across freeze-thaw cycles, 50-year limited residential warranty. The right choice on shaded north-facing slopes and shoreline decks where condensation and rain dwell on the board surface.
Mineral-rich core resists moisture absorption better than wood-flour composites and stays cooler underfoot than dark PVC. Holds dimensional stability over long unsupported spans where slope framing forces wider joist bays.
Heat-and-steam treatment alters cell structure to produce a stable, decay-resistant board from FSC-eligible North American ash. We specify it where homeowners want the look and feel of tropical hardwood without sourcing through Ipe channels — Brazilian Ipe (Handroanthus spp.) carries CITES Appendix II restrictions and increasingly unreliable PNW supply.
Slope, soil, and jurisdiction differ measurably across the MSA. We publish a focused page for each of the three highest-velocity hillside service areas.
Alki, Genesee Hill, North Admiral, Highland Park, Pigeon Point. Steep-slope SFR parcels above 30% grade are common; the SDCI ECA permit overlay drives the engineering depth.
Read regional brief →Service AreaQueen Anne Hill north slope and West Queen Anne toward the Magnolia Bridge. Pre-1965 foundations frequently need updated R507.10 connections; cable rail preserves the territorial view envelope.
Read regional brief →Service AreaBridle Trails, Somerset, Cougar Mountain, Lakemont, Newport Hills. City of Bellevue permits at a >30 inch threshold with plan review included; engineered fill and glacial till change the foundation calculus.
Read regional brief →Bring a parcel address, a sketch, or a set of architectural drawings. We’ll respond with a feasibility read, a likely foundation system, and a permit-pathway estimate within two business days.
Our cost-cluster pages publish 2026 installed ranges with permit-fee, sales-tax, and tariff context broken out line-by-line — including the geotechnical and helical pier add-ons specific to ECA parcels.