Although wood is one of the oldest and most common construction materials, it’s typically perceived as weaker and more susceptible to fire than alternatives like steel and concrete. These fears have been codified over the past century by means of restrictive limits on the height and area of timber buildings.
Recently, wood construction has experienced something of a renaissance. Building professionals and government officials alike have been drawn to its sustainability credentials: timber stores carbon dioxide, can be fully renewable, and prevents pollution typically generated during the extraction and manufacturing of steel and concrete. Timber also offers unique design possibilities and architectural appeal.
However, fears about fire safety have continued to limit its use. Thankfully, a considerable amount of testing focused in Europe, Canada, and New Zealand has begun to convince designers and public authorities alike that wood can be as safe as steel and concrete for buildings. Height limits for wooden structures have been relaxed in some regions of the world, while others have introduced options for performance-based design solutions. Timber structures up to 30 stories high are currently in design in Norway, Austria, and Canada.
In an effort to fully understand the implications of this shift within the US market, Arup was recently commissioned by the nonprofit Fire Protection Research Foundation to conduct a multiphase study of fire safety in tall timber buildings. The report for the first phase, which focused on gathering information and identifying knowledge gaps, was released a few months ago. (It’s available as a PDF here.)
As part of this process, we compiled case studies of multistory wood buildings throughout history. The following examples give a sense of the possibilities of tall wood design — and where the industry might be headed.
Shanxi, China, 1056
The Yingxian Pagoda is a nine-story, 221-foot-tall pagoda located in the Shanxi province of northern China. Constructed in 1056, it is the world’s oldest existing multistory timber building.
Built on a thirteen-foot stone platform foundation, the structure consists entirely of wood. An exterior and interior circular arrangement of timber columns support the five visible stories and four additional floors hidden within.
The pagoda has survived over 900 years of seismic activity, including more than seven strong earthquakes, with minimal damage. UNESCO describes it as “a miracle in the history of Chinese architecture.”
Sogn og Fjordane, Norway, 1132
According to UNESCO, “stave churches constitute one of the most elaborate and technologically advanced types of wooden construction that existed in North-Western Europe during the Middle Ages.”
Built around 1130 in present-day Sogn og Fjordane, Norway, Urnes Stavkirke is one of the oldest and finest remaining examples. Constructed partially from elements of another church built on the site a century earlier, it consists entirely of wood, with large columns and arches supporting the structure.
Vancouver, Canada, 1908
The six-story Leckie Building was constructed in 1908 in Vancouver, Canada. Built using a technique known as brick-and-beam construction that was popular in the early 20th century, it consists of a brick façade supported by a heavy timber internal structure.
The use of brick-and-beam construction allowed a large, open floor plan that was used for office and industrial functions for the Leckie Company, makers of footwear for soldiers during both world wars. The building went through seismic renovations in the early 1990s and currently houses offices, shops, and restaurants.
Brisbane, Australia, 1913
The Perry House is a seven-story, 122-foot timber structure composed of a heavy timber interior and brick façade. Constructed in 1923 in Brisbane, Australia, the Perry building is one of the oldest and tallest timber structures in Australia.
Brisbane businessman William Perry constructed this timber-based structure to house his family’s retail operations. It was recently converted into a boutique hotel.
Vaxjo, Sweden, 2009
Approximately ten years ago, the Swedish city of Växjö declared its intention to promote the use of timber in construction, beginning with the development of an area called Valle Broar. The first project to be completed as part of this initiative is an eight-story, 134-apartment structure consisting of seven timber floors above a concrete foundation and first floor.
The design uses glulam (glued laminated timber, a relatively new form of timber element consisting of separate layers of timber glued together) members and prefabricated solid wood frame construction for structural wall and floor supports.
It also includes instruments to measure deformation and track the vertical displacement of the structure over time. This is intended to better understand deflection concerns for tall timber buildings. More than a year and a half after construction, sensors indicated that the building had moved by only 20mm, calming displacement fears. Learn more here.
London, United Kingdom, 2009
London’s Stadthaus, designed by Waugh Thistleton Architects, was completed in 2009. Also known as Murray Grove, Stadthaus is a nine-story residential apartment complex consisting of a reinforced concrete ground level topped by eight stories of cross-laminated timber (CLT) panels, another recent innovation in the wood world. CLT was selected due to its strength, high-quality due to production off-site and rapid erection due to prefabricated building elements. The prefabricated panel system allowed a team of four carpenters to build the superstructure in less than four weeks.
The project generated substantial international interest in the use of CLT for prefabricated residential buildings.
London, UK, 2011
2011’s Bridport House, the UK’s first building constructed entirely from CLT, represents the first phase of a regeneration project in London’s Borough of Hackney. The eight-story residential structure, designed by Karakusevic Carson, consists of prefabricated CLT panels topped by a concrete slab (for acoustic purposes).
The decision to use CLT rather than steel or concrete stemmed from weight concerns due to the presence of a storm relief sewer under the site. This also reduced foundation demands, as the use of CLT resulted in a lighter building. The panels were edge-glued to make connection locations more air- and water-tight, improving acoustic and fire performance.
Prefabricated panelized construction resulted in a construction time of 10 weeks, less than half the estimated time for a concrete structure.
Bad Aibling, Germany, 2011
Designed by Schankula Architekten and completed in 2011, this eight-story Bavarian building is one of a number of mid-rise buildings being constructed in Germany. H8 is composed of CLT floors and walls, with a concrete core provided at the request of the building department.
Prefabricated CLT panels are covered in gypsum board to provide additional fire protection. The panelized system permitted a construction assembly time of approximately 16 working days, or one story every two days.
Melbourne, Australia, 2013
The Forté Building is currently the world’s tallest modern residential timber building. Constructed by Lend Lease, the ten-story apartment building uses prefabricated CLT panels for the primary structure. A concrete floor slab was added for fire separation and acoustic performance.
The project team reported significantly faster, safer, and higher-precision construction with the prefabricated system than typically achieved with traditional materials.
Fire testing during the design phase demonstrated that the depth of the CLT panels used would provide sufficient fire resistance. Despite this, the design team added gypsum to many wall and ceiling elements for additional noncombustible protection.
Life Cycle Tower One
Dornbirn, Austria, 2012
Life Cycle Tower One was the first building from Cree, an Austrian construction company dedicated to urban wood construction. The project started as an Arup feasibility design for a 20-story heavy timber building, and resulted in the construction of an eight-story office building.
The structure features post-and-beam construction (in which horizontal beams transfer structural loads to vertical posts) with large internal and perimeter glulam columns. These are combined with a concrete core for stability as well as hybrid timber-concrete composite floor slabs for fire separation and acoustic performance.
A second Life Cycle Tower was completed in Vandans, Austria in June 2013. Plans are underway for more around the world, including Oakland and Vancouver.
Milan, Italy, 2013
Via Cenni, the first CLT project to be built in an earthquake-prone area, was completed in late 2013. The four-building social housing facility consists of nine stories of prefabricated CLT construction.
To keep inhabitants safe in case of seismic activity, the design includes large nailed web plates and self-tapping screws to facilitate a continuous load transfer between structural elements.
As observed in previous examples, gypsum board protective covering was used despite sufficient inherent fire resistance in the CLT structural panels.
Seattle, Washington, USA, 2013
The Bullitt Center is a six-story office building located in Seattle, Washington. Completed in 2013, it is one of the most ambitious projects to date in terms of sustainability. The building design aims to improve long-term environmental performance and promote renewable and sustainable technologies.
The facility is one of the first timber buildings designed to meet Living Building Challenge standards, which require buildings to be self-sufficient for energy and water for at least 12 continuous months, in addition to meeting green material standards.
The use of timber structural material – in this case, glulam post-and-beam construction and timber-concrete floor slabs – contributes significantly to the project’s sustainability goals. The Bullitt Center presents a case study for other projects attempting to achieve Living Building certification.
Wood Innovation Design Centre
Prince George, Canada, 2014
Scheduled for completion in late 2014, the Wood Innovation Design Centre is a six-story commercial building located in Prince George, Canada. Designed by Michael Green Architects, it maximizes timber structural elements through the use of glulam post-and-beam construction with hybrid timber-concrete floor slabs and a timber core.
When completed, the building will be the tallest timber building in North America, at a height of approximately 90 feet. It will house businesses and research facilities dedicated to growing British Columbia’s wood products industry. (The building was partially funded by a Canadian government endowment of $2.25 million CAD.)
Coming soon to a city near you?
Although the Bullitt Center and Wood Innovation Design Centre are pioneers for tall wood construction in North America, the success of these and other structures is provoking interest in many other quarters. Most recently, the United States Department of Agriculture announced a large-scale program aimed at bolstering the country’s wood building industry, including training programs for architects and engineers, a timber high-rise design competition, educational seminars and conferences, and more. So who knows: a tall timber home or office may be in your future.