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September 28, 2018
Owner/developer: David & Aya Kovanen
Team: Innovator Corporation, general contractor; Turnstone Construction, concrete contractor; David Kovanen and Angelo Architecture, architects; CT Engineering, structural engineer; Corliss Resources, ready-mix supplier
This project required tucking a large contemporary great room beneath a 90-year-old Tudor estate without impacting the existing historic structures.
The solution was to build into the side of an imposing Puget Sound cliff utilizing tall concrete shoring walls and then erecting a commercial-scale concrete structure to support the loads above.
In the process of achieving these goals other applications of decorative concrete were employed, including the construction of a naturalistic mineshaft entry rendered in sculpted shotcrete, artistically finished exterior patios, and polished interior floors. Additionally, a concrete structure was built at the tideline below for housing boats, with its concrete construction protecting the structure from the strong tidal forces that pound against Browns Point in Tacoma.
The finished result is a building that virtually disappears into the side of a 45-foot-high cliff. The project features a multitude of concrete techniques and finishes:
?? Artistic shotcrete at the building entrance that was sculpted as a rock formation with weathered timbers that appear as though one is entering a shaft blasted into native rock. This created a convincing theme that the project was an old mining operation that was “discovered” and remodeled. The mineral that was supposedly mined was “gingkonium”, which to this day faintly glows through cracks between the rock fissures (it is actually hundreds of fiber optic strands embedded into the shotcrete).
?? The green roof is large by single-family residential standards. The roof is structural concrete supported by a 45-foot-long beam, and it utilizes two novel technologies: Insulated concrete forms (ICF) and Xypex waterproofing. The ICF technology ensures this concrete roof is both strong and lightweight. The Xypex provides a secondary waterproofing that is integral within the concrete.
?? The concrete walls use a modular ICF forming system, which solved the challenge of limited backside access and helped minimize the number of cold joints and hence the number of lifts required.
?? Architectural concrete surfaces remain exposed on both the interior and exterior of the building. Transitions from sacked concrete walls to level 5 drywall are indistinguishable.
?? The highly polished concrete floor is a deep grind with aggregate cut to be fully exposed. Beautiful colors in the aggregate are revealed by the deep cutting. The mirror-like, high-gloss finish of the floor makes the entire room incredible.
The 12-by-45-foot window facing Puget Sound is reflected in the concrete floor’s mirror finish. Additives have minimized hairline cracking. The floor is slip resistant, requires no waxing or polishing, and has a shine equivalent to that of polished marble.
?? The “star patio” at first glance seems to be like any other polished concrete patio. Yet buried in the concrete slab are 1,250 fiber optic strands that change colors, twinkle, and appear as stars at night. Invisible when off, they explode into color when illuminated.
?? Extensive shoring was required. Controlled density fill (CDF) stabilized the project excavation. The soldier pile shoring and footings were shotcreted to retain the cliff face. Grouting injected into the tie-backs helped provide the structural support for the project. CDF also replaced soil backfill because of limited access.