Architect Andrew Waugh, director of London-based Waugh Thistleton, is evangelical about saving the planet—yet adamant that his practice's work should not “reek of sustainability.” The firm's recent 52 Whitmore Road project, a mixed-use building that cantilevers over North London's Regent's Canal, shares more with Italian rationalism than with the organic structures of late American architect Bruce Goff or the solar roofs and wind cowls of British architect Bill Dunster, both avid environmentalists at the margins of mainstream practice.
Fed up with the scorecard approach to green design inherent in the BREEAM certification system (Britain's answer to LEED), Waugh searched for a building material that could also sequester carbon. That material was cross-laminated timber (CLT) from Austria, an engineered wood product made of kiln-dried finger-jointed spruce strips glued under pressure in perpendicular layers to form slabs that can be used as load-bearing walls and floors.
Waugh Thistleton first used the material at Murray Grove, a nine-story residential building in Hackney, East London. It was the world's tallest CLT structure when it was completed in 2009. Since then, the firm has further explored the use of the material in several projects, the latest of which is Whitmore Road. The project is a cooperative venture between a community trust and three individuals: a photographer, a café owner who runs a nearby coffee shop on the canal, and Waugh. The six-story, 11,000-square-foot building houses two floors of offices for the trust, the photographer's studio above, and three triplex apartments on top. Waugh and his family live in one of the apartments.
A dual entrance arrangement cleverly separates office workers from residents, one of the project's numerous thoughtful details. A metal security gate—leading to the offices—frames a glimpse of the canal, not otherwise visible from the street, while residents slip through another gate to climb three flights of stairs in a straight run along the rear of the building to reach the apartments. Sweet chestnut cladding wraps the exterior, and the open board detail adds texture while allowing the timber to breathe. Likewise, the diamond-patterned brick pavers, commonly used in stables, add texture to the entrance area.
In the offices, the underside of the approximately 5-inch-thick first-floor CLT slab is exposed, revealing a simple steel angle detail devised to tie the wood, which cantilevers 5 feet over the canal, to the concrete walls below. “We always lift the timber off the ground,” notes Waugh. The timber structure weighs approximately one-fourth of a comparable one in concrete, permitting fewer and shallower foundation piles, saving both money and carbon.
The photographer's requirement for a 21-foot-tall, 2,000-square-foot column-free studio posed a structural challenge because CLT lends itself to tighter, honeycomb-like floor configurations. The problem was solved by treating the front and rear facades as beams and stiffening them with the walls that separate the apartments above.
In addition to sequestering carbon, CLT offers other benefits. Off-site prefabrication means that waste is reduced and on-site construction times are shortened by up to half, says Waugh. However, he warns, the design phase can last longer, because all issues, including openings for mechanical and plumbing services, must be resolved before fabrication. Another critical consideration is having adequate site access for lifting the panels into place by crane, points out Richard Neuhercz, a structural engineer with KLH, Whitmore Road's CLT supplier. The project's construction costs were about $240 per square foot, (excluding kitchens and baths, which were beyond the contract scope), remarkable for London.
European production of CLT has grown tenfold since 2009, and surpassed 650,000 cubic yards last year. After a slow start in the United Kingdom, a plethora of CLT projects are now in the pipeline. Waugh invited 200 architects to Murray Grove's opening; only four showed up. Initially used mostly for schools, CLT has now penetrated the residential sector, with six buildings taller than 10 stories under way across the country. In addition to a residential tower to be completed next year, Waugh Thistleton is working on two other projects in London that use CLT—a 182-room hotel near the Liverpool Street station and a six-story mixed-use development near their Shoreditch office.
Although British firms building with CLT have had to import the material, a team at Napier University in Edinburgh is exploring its manufacture from Scottish Sitka spruce; commercial production is likely to start within the next 24 months. The market for CLT in North America, according to Waugh, is where Britain was 10 years ago. But he predicts “they will catch up and take over.”
The Architects' Journal.
Formal name of building: 52 Whitmore Road
Location: 52 Whitmore Road, London N1 5QG
Personnel in architect's firm who should receive special credit:
M&E Consultant: Michael Popper Associates
General contractor: Jerram Falkus
Photographer(s): Will Pryce
11,000 square feet
Manufacturer of any structural components unique to this project: KLH UK
Wood: British Sweet Chestnut Cladding
Moisture barrier: Visqueen tanking