An extension to the Grade-II listed Brandlehow Primary school is one of the first education projects in the UK to use the prefabricated wooden Finnforest Merk LenoTec system. Erno Goldfinger's original 1952 single-storey building in Putney, south-west London, favours natural lighting, ventilation, prefabrication and easy erection without heavy machinery. Londonbased Team 51.5¦ Architects has reinterpreted Goldfinger's way of thinking, in both layout and construction technique. Opened in January 2006, the extension consists of a wooden building that is linked by a glazed corridor to the existing school.
Subcontractor Eurban erected the building's prefabricated solid-timber structure over a two-day period, fixing the elements to the concrete base through a bolt-and-bracket system. Every construction element is manufactured separately using Finnforest Merk, which allows greater design flexibility. Sheets are built up in layers of untreated, soft timber which are connected symmetrically crosswise; between three and 17 layers are used to create a thickness range from 51mm to 300mm.
For the Brandlehow project the thickness was 115mm. There was a six-week lead to cut the wood into the predefined wall designs at the factory in Germany. With a span of up to 5m, the classroom structure is steel-free and only two beams are used within the structure. The solid timber construction provides climatic stability due to the thermal mass of the solid timber wall. LenoTec offers a higher thermal mass than wooden structures; a green roof, installed by Bauder, also enhances the thermal mass. Two layers of 50mm Rockwool insulation and cedar cladding have been added to Finnforest's external wall. The airtight solid-timber structure has enabled acoustic and thermal performances in excess of those required by the respective Building Regulations.