Fifty years ago, Many apartment buildings were built in the International Style, tall flat slabs of buildings with efficient layouts. Now Acton Ostry Architects are using this iconic 20th century style to build the world's tallest timber tower using a truly 21st century material, Cross laminated Timber (CLT). I have described CLT as the dream material: it's made from a renewable resource, it sequesters carbon, it is strong enough to replace wood and concrete in higher buildings, and right now, it helps use up some of the billions of board-feet of mountain pine-beetle infested wood that will rot if we don't cut it and use it fast.
The building is a new student residence for the University of British Columbia that the University president says is "a living laboratory for the UBC community. It will advance the university’s reputation as a hub of sustainable and innovative design, and provide our students with much-needed on-campus housing.” At 53 meters (174 feet) it will just squeak in as the tallest plyscraper.
More precisely, according to the architects,
The structure is comprised of a one storey concrete podium and two concrete cores that support 17 storeys of mass timber and concrete structure. Vertical loads are carried by the timber structure while the two concrete cores provide lateral stability. The floor structure is comprised of 5-ply CLT panels that are point-supported on glulam columns on a 2.85m x 4.0m grid. This results in the CLT panels acting as a two-way slab diaphragm. The structural concept is similar to that of a concrete flat plate slab. To avoid a vertical load transfer through the CLT panels, a steel connector allows for a direct load transfer between the columns and also provides a bearing surface for the CLT panels. The CLT panels and glulam beams are encapsulated with gypsum board to achieve the required fire resistance rating.
No doubt the steel and concrete people will be out in force calling this a firetrap (thats what all the commenters are saying in the Vancouver Sun) However it is not. The architects note that "The conservative approach used for the design of the project is equally as safe as that for high rise buildings using a concrete or steel structure. "
The building is comprised of a series of repetitive, highly compartmentalized small rooms so that in the event that a fire originates in one suite it is extremely likely the fire would be contained in the compartment in which it originated. To enhance compartmentalization, the typical one-hour fire separation required by the building code has been increased to two hours. Studies have shown that automatic sprinkler systems are effective in controlling over 90% of fire incidents. For this project an automatic sprinkler system with a back-up water supply offers additional protection for occupants, as well as for firefighters, for events that might originate during an earthquake, as the sprinkler system would remain operational.
Then there is the basic characteristic of CLT: It doesn't burn very well.
Due to the characteristics and properties of charring, mass timber construction provides an inherent level of fire-resistance. Large timber members are difficult to ignite and if they do ignite they burn slowly. The CLT and glulam components used for the project have an inherent degree of fire-resistance that has been enhanced through encapsulation of the mass wood with three to four layers of fire rated Type X gypsum board, dependent on location.
There is a reason for that sixties flat slab look: "To comply with university planning requirements the design reflects the character of International style modernist buildings on the campus."
The base is wrapped with curtain wall glazing, coloured glass spandrel panels and transparent coloured glass. An extensive CLT canopy runs the length of the building. The façade is a prefabricated panel system comprised of white and charcoal panels punctuated by floor-to-ceiling clear-glazed openings with accents of coloured blue glass. Glazing wraps the corners to dematerialize the edges of the building. Further accentuating the vertical expression are a series of vertical splines that rise up to a metal cornice that crowns the building.
A real mix of a classic design from the past and the material of the future.