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Architects: architects—Alliance
Design Team: Peter Clewes and Gerry Lang
General Contractor: Cityzen, Toronto, Ontario, Canada
Client: Private
Photographers: doublespace photography

Architectural Merit & Creativity

Escarpment House revisits a fundamental strategy of modernist architecture: the precise deployment of a minimal palette of stone, glass, metal to make a statement about the relationship of building to context. This project inserts a singular built form into an extraordinary landscape to encourage contemplation and allow one to appreciate both more clearly.

Escarpment House sits slightly below the brow of a dramatic 30% slope overlooking a spring-fed pond set into fields of native grasses, shrubs, and trees. A multigenerational retreat for a couple, their adult children, and grandchildren, the 1,022 m2 bar building is programmed with multiple interior and exterior family gathering spaces, private bedrooms and en suites. The house is rendered in a restrained palette of locally quarried, honed and cleft-finished Algonquin limestone, narrow anodized aluminum fascia, and fully glazed walls that merge interior and exterior space and frame views through the house and into the surrounding landscape.

Functionality & End-Use Suitability

An axial arrangement of rooms and circulation knits together exterior and interior space. The entrance is marked by a water feature emerging from the structural wall that bisects the long axis of the house. This feature wall defines public and private programs: living room, dining room, outdoor barbecue and dining terrace to the southwest, bedrooms and guest suite to the northeast. Following the stone-clad wall, one passes through the home to emerge at broad steps descending to a terrace, pool, and fire pit. Bedrooms let out on a limestone terrace that communicates with the pool steps. The SW-NE orientation ensures that interiors receive indirect sunlight throughout the day, while deep roof overhangs shield dining and bedroom terraces from the afternoon sun. A pond house 100m downslope sits adjacent to a spring-fed pond.

Quality of Engineering Design

A tremendous level of technology and craft was required to address the distinct structural challenges concealed within this restrained and straightforward parti. The 60m x 13m x 300mm roof slab used 36 tonnes of concrete and 27 tonnes of steel bar. Formwork was left in place for 8 weeks to eliminate sag and accommodate the careful installation of ~100m of triple-glazed mullion-less windows. The floor slab emerges from the slope, supported on a 6m tall, buried retaining wall that conceals below-grade garage and mechanical rooms while raising the swimming pool level with the main floor of the house. The principal structural wall bisects the floorplate near its midpoint and traverses the house from the main entrance to the pool terrace. The wall is insulated to avoid thermal bridges and preserve an unbroken line from northwest to southeast.

Innovative Construction Techniques/Solutions

The roof slab, 30m x 13m x 300mm, is supported on a continuous wall running east to west and terminating in four 175mm steel pipe columns and a concrete pier. The result is a 'floating' roof with minimal points of support to interrupt the open living/dining/kitchen space. To maintain a flat roof expression without beams or drop panels, steel X-formed capitals, cast into the slab's thickness, distribute extreme loads on the four columns. These capitals are custom-fitted with connections to reinforcing steel and post-tensioning rods. Several materials and strategies worked in concert to minimize deflection:

•Specifying a specially formulated concrete mix designed to work with the dense reinforcing steel network

•Formwork remained in place for 56 days (compared with the four-day industry standard)

•Cambering an 8x8m cantilevered corner at the west end of the slab

As a result, roof slab deflection was a mere 6mm—25% of construction standards—and the cambered corner deflected into a flat plane after curing.

Specialty interior concrete mixes throughout the interiors create a highly reflective, smooth surface, with a 100mm topping on interior floors conceals the radiant floor heating system. Floor grilles and mullions are aligned with the floor, minimizing the profile of the horizontal mullions and creating a ‘frameless' glass wall at all window openings.

The infinity pool is supported on shear walls emerging from the site's 30o slope, raising it approximately 6m above the original grade and keeping it co-planar with the residence's south-facing terrace.

Sustainability

The size and openness of the house interiors, and the high degree of transparency, create challenges for delivering an energy-efficient building. Nevertheless, Escarpment House employs a series of sustainable strategies: including a geothermal system supplying conditioned air, hot and cold water; poured-in-place concrete structure that acts as a heat sink; extremely deep roof overhangs to controls passive solar gain; triple-glazed Low-E window assemblies; low-flow toilets and energy-efficient fixturing; and locally sourced building materials and finishes.