Cross-laminated-timber residential high-rise under construction in the heart of London
The construction of a groundbreaking eight storey residential high-rise, Bridport House, from Stora Enso’s cross-laminated timber (CLT) panels is currently underway in the London Borough of Hackney. The 10 week assembly phase is due to be completed by the end of December 2010.
Comprising 41 units, Bridport House replaces a 1950s block of flats and is seen as the kick-start to a wider regeneration of the borough’s run down estate. It is the first time that cross-laminated timber has been specified in the UK for an entire high-rise structure including the ground floor. Though the material has been used in high rise applications before now, previously the ground floor has been constructed from concrete.
The specification of CLT as the main structural material has helped to meet key sustainability objectives for the Bridport House project. By building with timber it is possible to offset emissions resulting from the construction process as timber acts as a carbon sink with each home containing approximately 30-40 m3 of timber which is equivalent to over 30 tonnes of CO2.
Stora Enso’s CLT panels have also provided a solution to a very specific issue of weight: Bridport House has a storm relief sewer running directly under the site making it unsuitable for a heavy traditional concrete frame structure. The properties of CLT’s engineered strength combined with its light weight have made it the ideal solution to overcome this problem. The structure has been designed in a way that the load bearing CLT panels are placed in a variety of positions on each floor, thus spreading the load. Because of this, it has also been possible to double the size of the replacement structure with only a 10% increase in overall weight.
What is CLT?
CLT panels are produced by glueing wooden lamellas crosswise together as enormous airtight elements. The prefabrication of the CLT elements offers a minimum of assembly time on site. Stora Enso’s CLT differs from other brands of CLT because it requires only a minimum of three layers to achieve air tightness due to its glueing process – not five or seven as is often the case. Also, the panels are edge glued using specialist technology which further increases their airtightness, acoustic and fire performance as well as making them watertight. This technique has the additional benefit of increasing the temporary weather protection when building in the winter months.
Stora Enso is producing CLT elements at its purpose-built factory in Bad St Leonhard, Austria, using locally sourced PEFC certified spruce.
More information on CLT solutions: http://www.clt.info/