In the 1950s, modernist architect Ernö Goldfinger developed a method for concrete prefabrication. Brandlehow Primary School in Putney was one of two schools he developed using his system. The concrete was considered to have a "weight and grandeur" usually lacking in school buildings from that era. Goldfinger's system used repeated concrete frames with vertical and horizontal glazing bars, creating an open look.
In the 60s, Goldfinger was invited back to develop a classroom extension to the school, which he designed and built using a different system. This extension had far less glazing and was not prefabricated.
The local planning authority, Wandsworth Borough Council, recently acknowledged the need for yet another extension to the school. They commissioned the London office of team 51.5° architects to design the new classroom next to Goldfinger's extension. Because Goldfinger's own extension had no direct reference to the original building, the team decided their addition shouldn't either.
They maintained Goldfinger's pattern of corridor and classrooms but added a more contemporary look. Additional continuity comes from team 51.5° choosing prefabrication for construction.
According to architect Franziska Wagner, the team's consideration of sun, light, natural ventilation, and contemporary materials are consistent with principles outlined in "Classroom of the Future" by the UK Department for Education and Skills (DfES). This initiative aims to challenge current school design practices and test new ideas for application in future buildings.
The new Brandlehow addition consists of a wood building linked by a glazed corridor to the existing building. The FinnForest Merk solid wood walls are highly insulated and clad with cedar boarding.
Swenn Geiss of team 51.5° architects explains: "We have developed various openings in the building that allow for different light qualities in the room. A large opening to the south, which is protected from excessive solar gain by a new tree, juxtaposed with a rooflight, bringing in constant north light."
The FinnForest Merk system consists of untreated softwood that is laminated in 3 to 17 layers. The elements — such as entire walls — can be delivered in dimensions up to 15 feet-9 inches (4.8 meters) wide and 66 feet (20 meters) long. Thicknesses range from 2 to 12 inches (51 to 300 millimeters). For the Brandlehow project, the wall thickness was 4-1/2 inches (115 millimeters).
One advantage of the prefabrication system is that it requires no grid or predefined sizes. Every component is designed and manufactured separately. The subsequent jobsite assembly can be carried out quickly, minimizing labor costs.
General contractor Cuttle McLeod Construction started on sitework and the foundation in June 2005. It took six weeks to have the wood cut into the predefined wall designs at Merk's factory in Germany. When the wood components were delivered, the main core of the building was erected in just two days by subcontractor E-Urban.
The wooden structure is fixed to the concrete base through a bolt and bracket system. With a span of up to 16 feet (5 meters), the rest of the classroom structure is steel free and includes only two beams. Although the classroom is one-story, the FinnForest Merk system can also prefabricate multistory structures.
The solid wood construction, being both thermally massive and insulating, provides climatic stability within the classroom. A green roof installed by subcontractor Bauder also enhances the thermal mass. Two layers of 2-inch (50-millimeter) Rockwool insulation and cedar cladding have been added to the exterior wall. The acoustic and thermal performance exceed those required by regulation.
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