Steel Treehouse

La Tour de Bbelles, Loughborough Township, Ontario

Architects Barbara Dewhirst and Andr Lessard

The construction of seasonal residences in Ontario’s lake-studded cottage country poses a unique problem: how to build on sensitive sites without degrading the very environment that their owners set out to enjoy. With increased demand and pressure for the development of recreation property, parts of Ontario’s prized vacation spots are taking on the character of distant suburbs, no longer offering the sought-after rejuvenating peace of a nature retreat.

A project on Otter Lake at the southern edge of Frontenac Provincial Park provides a conscientious alternative to intrusive and aggressive development on Ontario’s fragile lakefronts. Designed by Toronto architects Barbara Dewhirst and Andr Lessard for their own family, the unorthodox cottage adopts a variety of strategies to minimize impact on its virgin 32-acre site.

This is not only true of the building in its finished form, but also of its construction. The architects explain that the solution was driven by two primary considerations: building lightly on the land and taking advantage of views to the lakefront. Local bylaws prohibited construction within 100 feet of the lake, a situation often dealt with by clearing trees to create view corridors from the cottage. Here, in order to minimize the removal of trees, the architects decided to maximize views of the water by building high. The desire to limit the building’s impact on the site also resulted in the development of a design that would minimize footings and other construction at the ground plane. The combination of building high and reducing the building’s footprint to only a few points of contact drove the decision to build in steel rather than wood–the usual choice for cottage construction.

In order to keep the well-wooded property as intact as possible, the road into the site has been held back to about 300 feet from the cottage, providing a substantial buffer of undisturbed forest. Construction materials and equipment had to be carried in by hand; consequently, heavy sections of structural steel posed a major problem. In collaboration with structural engineer Eric Jokinen, Dewhirst and Lessard developed a structural system of much thinner and lighter 10 gauge steel sheet, folded to provide structural strength and designed to be bolted together on site. The architects liken the structural system to “a giant Meccano set,” reflected also in Jokinen’s playful name for the project, La Tour de Bbelles, which roughly translates as “the tower of metal toys.” No individual member exceeded 10 feet in length, and none weighed more than 25 lbs., so that the structure could be carried in and assembled by local carpenters.

In addition to its inventive structural solution, La Tour de Bbelles breaks with cottage convention in a variety of ways. The triangular plan, for instance, meant building three footings instead of four. The form was also driven by the fact that the best views toward the lake are to the north, and the triangular plan allows the two other sides to maximize exposure to the southeastern and southwestern sun. Each side is about 30 feet wide, and with structure confined to the corners, each aspect benefits from ample access to light and view.

The design was also intended to emulate a treehouse, and perched on its steel stilts, the building clearly evokes this source of inspiration. The living spaces are on two levels, each a compact 450 square feet. A gangplank leads to the first floor, which houses bedrooms and a bathroom, whose composting toilet negated the installation of a more environmentally intrusive septic tank. The second floor, accessed by a compact, space-saving steel stair, accommodates kitchen, dining and living spaces. The open plan allows for maximum flexibility and generous views of the lake and surrounding forest. Beneath the cottage, nestled between the steel supports and rocky outcroppings, a large deck provides a direct relationship to the wooded surroundings.

The exterior is finished in fibre cement board and dark-stained tongue and groove pine siding, blending in with the bark of surrounding tree trunks. Inside, warm wood finishes complement the crisp black-painted steel.

Dewhirst and Lessard explain that the cottage satisfied a desire shared by many architects: to design and build their own home, a much more difficult prospect in the city than in a seasonal residence. In addition to its environmental benefits, the modular design was well suited to building in stages, allowing for incremental growth over a number of summers, reducing pressure not only on the building site and its surroundings, but also on budget and schedule. MP

Client: Barbara Dewhirst and Andr Lessard

Architect team: Barbara Dewhirst, Andr Lessard

Structural: Eric Jokinen

Area: 900 square feet

Budget: $97,000 (including site services)

Completion: Summer 2001

Photography: As noted