Containing 3,800 cubic metres of timber, the William Perkin High School is the largest cross laminated timber building in the UK. The scale of cross laminated timber (CLT) buildings continues to grow with the completion of William Perkin High School in London, with the four storey complex becoming the largest CLT building in the UK, containing 3,800 cubic meters of timber. Designed by Feilden Clegg Bradley Architects, with Ramboll supplying structural engineering expertise, the £20m development is a showcase for timber engineering thanks to its sheer size, exposed timber structure and bold architecture.
Designed to meet the local demand for secondary school places, William Perkin High School now provides facilities for 1200 students, aged 11-18 years, and offers an innovative curriculum specialising in sciences, music and languages.
Choosing cross laminated timber
The transformation of the site into the new ‘Very Good’ BREEAM rated William Perkin High School had to be completed in just twelve months but the original design, conceived as a concrete structural frame, would not permit such a tight deadline. The design was radically revised when Ramboll, together with Kier construction and KLH UK, proposed a CLT solution, demonstrating to the client significant reductions on substructure works and the superstructure programme while also shortening fit-out times. This resulted in pupils being able to enjoy their new school 10 months after works began on site, with the site fully completed and opened in Spring 2014, two months ahead of schedule.
Ramboll utilised specialist structural engineering techniques to develop the timber design and drew on 10 years’ experience in designing timber structures to produce the structural design for the building’s frame and panels, with full connection details.
The building footprint, which sits adjacent to the busy A40, was carefully positioned to maximise its green outlook and surrounding air quality while minimising solar gains. Careful attention to the acoustic performance of the classroom facades has enabled the school to be positioned adjacent to the A40, a site that would otherwise have been undevelopable for this type of building. Communal areas, such as the hall, sports hall and dining areas are located to the south side facing the road, while classrooms are to the north and form a triangular space on plan with large central north facing roof lights above the atrium spaces.
Large areas of the timber structure are exposed as architectural features, the most striking of which are the main atrium spaces which include timber walls, floating feature staircases and visible roof lights. Not only has this provided a great aesthetic value to the building but it has also yielded many savings in interior wet trades as the large timber panels do away with a significant quantity of interior blockwork partitioning and plastering.
Future flexibility and adaptability was integral to the design. The overall design of the structure enables classroom configurations to be easily reorganised, as the walls between classrooms are not structural and can be moved without major revision to the building. Solid timber loadbearing walls are located where removal is least likely, though further openings can be formed within the timber if required by future rearrangements.
The majority of the building’s superstructure and architectural features are formed using CLT, while a number of key elements are formed from glued laminated timber (Glulam). More than 1,700 tonnes of CLT, covering 22,500 square metres were used in the construction and the choice of CLT and Glulam, rather than concrete, resulted in fewer and less disruptive materials deliveries to the site which is located in a residential area. Above ground, the floors are 230mm thick and span some 7.5m. Walls are 180-208mm thick on the lower levels, decreasing to 95mm at the top floor, saving weight and reducing cost.
The CLT was fully coordinated with the MEP systems with some of the atrium panels even arriving at the site with decorative openings for the air circulation predrilled in them, removing the need for separate panels to be procured and fixed.
The school embraced the technology and is extremely impressed with the end product. They were so inspired by the timber building that they commissioned a large CLT reception desk to welcome visitors into the building. Associate Head Teacher Keir Smith said at the opening: “The building is superb and we were delighted that it has opened on time without a hitch.” The pupils are also excited about their new school. student feedback is full of positive comments, such as ‘It is very spacious and the timber makes it look good’ and ‘The building makes me feel relaxed, warm, chilled and grateful knowing that this place has been made for us’.