A vertical STEM

A new science and maths building at Charterhouse school in Surrey provides an appropriately ‘vertical’ form of chimneys and roofs to tie in with the historic architecture on the site, but also one with key functional benefits, as James Parker reports

Towards the end of 2009, Design Engine Architects were approached by Charterhouse, one of the UK’s pre-eminent independent schools, to create what would be a landmark building in a prominent part of the school’s site in Godalming, Surrey.

While the project would evolve significantly beyond its initial remit of providing a new chemistry facility into being the first phase of a wider STEM (Science, Technology, Engineering and Maths) project, somewhat unusually the new building’s striking design would remain largely unaffected, as project architect, Matthew Vowels, explains to ADF. The completed project, with its three distinctive chimneys, “is very close to those original sketches, which is fantastic,” he says.

“The client’s been very supportive of the architecture, taking a best value approach to design and specification.”

This was especially comforting, because creating a contemporary design appropriate for its technical academic speciality, nestled in a prestigious and historic campus of the buildings, was inevitably going to be a challenge. The site includes a variety of Gothic Revival and neo-Gothic buildings designed by architect Philip Charles Hardwick, many with tall chimneys and steeply pitched roofs, which the new building references without pastiche.

The practice won the original competition to design the new facility in 2009, beating strong competition including Hopkins, Belsize Architects, Panter Hudspith, and Pringle Richards Sharratt. The project was put on hold however before being restarted in earnest in 2015 as a more all-encompassing STEM centre, says Vowels. In the intervening years, Design Engine delivered two other buildings on the site – an extension to dining facilities and a student accommodation block.

In addition to chemistry labs, the new expanded brief included maths classrooms (co-located with science for the first time at the school but flexibly designed for later conversion into biology classrooms), plus a refurbishment of the school’s existing STEM accommodation – to be carried out in a future phase.

Brief & site
Founded in 1611, Charterhouse had a goal to ensure it remains at the forefront of educational progress, and this project plus later phases are a major part of realising that goal. Design Engine Architects commented: “The school’s aim was to revolutionise the way science and mathematics subjects are taught at Charterhouse by fostering inter- and intra-departmental collaboration.”

The building, which doubles space for STEM provision at the school, lies near the north eastern perimeter of the site, backing on to the sports field, and is therefore very prominent – putting an even bigger focus on getting the design right. The site is “surprisingly tough,” said Vowels, being a focal point of the vista from the school’s main entrance on Prince’s Drive, but the designers grasped the opportunity to “repair” that vista. Over the years the view had deteriorated somewhat, the grand historic buildings sitting adjacent to a “collection of lower quality buildings.”

The project architect explains how the approach of enhancing rather than creating a strident contrast with existing buildings helped ensure the design remained a viable option from the start, to the project’s subsequent reanimation. “One of the initial competition sketches we did was the view from the main entrance. It was very much about complementing what was there.”

Forms & materials
The two-storey brick-clad composition features three steeply pitched roofs and chimneys, expressing the six chemistry labs below – creating a subtle but important architectural link to the original campus, and in so doing creates a striking, but contextual addition. As well as being appropriate to its context, the resulting form also provides the appropriate volumes to deal with the internal and functional requirements of the educational facilities housed within.

Part of the client’s brief was the avoidance of flat roof products, which led to the entire roof being finished in zinc standing seam. “They wanted something that was of high quality, and also had longevity,” said Vowels. In addition, he explains that the whole structure being of one material, down to gutters and downpipes, minimised the interfaces of trades, and “kept it simple from an installation and maintenance perspective.” The subtle brown tone of the zinc roof (supplied by VMZinc) also tied in well with other buildings on the site: “It’s particularly similar to the adjacent ‘New Block’ and ‘Museum Building,’ but is also representative generally of the tile roofs throughout this part of the estate.”

The project’s evolved brief saw the building grow to be its final ‘L’-shape. It has a simple organisation of teaching spaces arranged around a generous central stair, and a further wing of teaching spaces linking to the existing school. The ‘L’ forms two sides of a new quad on the campus, which the project architect proudly says has proved an “enormously successful space.”

Most ground floor teaching spaces are accessed directly off a colonnade which runs around the inner facades overlooking the quad, and reflects the pre-existing design language of the school, says Matthew: “The school’s characterised by colonnades and quads elsewhere.”

The circulation leading off the quad also creates a new route to art, DT and modern foreign languages – “it’s created a lovely urban space within the centre of the school estate.”

The building is clad in a handmade brick from Haywards Heath (Michelmersh Freshfield Lane), “which tonally is a fantastic match for Charterhouse’s Bargate rubble stone,” and glass fibre reinforced concrete cladding to other facade elements references the stone quoins of the existing historic buildings.

Along the south- and west-facing colonnade, the curtain wall glazing and louvres have Siberian larch frames, “which brings warmth, softness and tactility to the facade,” adds Vowels. The designers carefully avoided overdoing the surface area when it came to glazing, in order to optimise light uniformity within for lab tasks, “We didn’t want to create too much contrast – a laboratory requires even, uniform lighting for experiments.” However, there is floor to ceiling glazing to the first floor circulation space and glazing (above 1000 mm) between it and the laboratories, borrowing light from both of the sides.

Servicing concealment
The steeper volumes of the roof have practical benefits too, aiding passive ventilation – an important facet of this project – and helping bring light deep into the plan thanks to high level opening windows next to the chimneys on the north facade. The forms also provide space to conceal the significant plant required for science labs.

“The chimneys work extremely hard,” says Vowels, “delivering all of the service requirements to the laboratories, while contributing to the architecture of the wider estate.” He adds that far from being a wilful design indulgence, “they are absolutely crammed full of services.”

This being a well-equipped tertiary level teaching facility, each of the seven chemistry labs have two fume cupboards for controlled experiments, which require air containing various chemicals to be extracted, at around 10 metres per second, and industrial-scale services. The ducts are roughly around 300 mm in diameter, and fans are approximately 700 mm x 500 mm x 500 mm.

Due to the bulky nature of this plant (it also includes ‘wet services’ distribution for the labs – natural gas, hydrogen, oxygen, Cat 1 and Cat 5 water), and the chemicals it’s extracting, it is normally placed outside the building envelope. However, here the architects achieved something that they believe is unique in such facilities, by enclosing it all within the chimneys, benefitting both aesthetics and ongoing function, but still maintaining safety.

“Normally the strategy for fume cupboard fans is to place them on the roof; if there is ever a problem, they are best placed when they are outside the building envelope,” says Vowels. “Given the context, that wasn’t going to be suitable on this project from both a maintenance and aesthetic standpoint.”

The fans are placed within the chimneys, but outside of the thermal and air-tight line, shielded by the brickwork, within a large cavity. As a result, annual maintenance inspections can be done from inside. “It was our instinct, and as we did further research we realised the normal approach needed changing,” says Vowels.

Also as part of the maintenance strategy, within the laboratories, services are distributed in a high-level acoustic pelmet detail and behind insulated removable panels, providing continuous access to services runs rather than through intermittent access hatches.

Teaching spaces
On the ground floor are four chemistry laboratories, three of which are identical, plus three maths classrooms designed to be turned into two biology labs in future phases. The first floor houses a further three chemistry labs, the main staff prep room and workspace, and a project room which enables long-running experiments to be mounted – “they can lock the door, and leave an experiment running, it gives them greater facility to try a wider range of experiments,” says Vowels.

There are two more maths classrooms on the first floor, which are however designed to be converted to biology in future phases, with services and drainage plumbed in to create future island benches for laboratories. There has been “a lot of dialogue with the school about how these spaces are going to be used in phase 2.”

The chemistry laboratories are unusually large, at around 110 m2, combining a standard ‘chalk and talk’ teaching space with an adjacent practical ‘wet’ space. “It’s one continuous volume, facilitating a very fluid movement from theory back to practical and vice versa, allowing a lot more crossover,” says the architect. The hope is it will allow for a more interactive as well as efficient way of teaching science, where theory can be taught while technicians are setting up the technical demonstration.

CLT & sustainability
Like the chemistry rooms, the well-insulated fabric is a hybrid, constructed from brick and block with a concrete frame offering thermal mass on the ground floor, but an exposed CLT frame on the first floor, supplied by Stora Enso. Vowels comments: “As a practice we enjoy using CLT, and we left it exposed in numerous locations as we felt the honesty that brought with it just felt appropriate for a teaching building – and a science building.” He adds that sustainability is the major driver for Design Engine’s love of CLT: “They’re essentially 200 mm thick timber sheets, so you’re sequestering a lot of carbon; it’s a very environmentally friendly way of constructing, which we are very keen to push.” In addition, due to the precise, offsite factory construction, the frame went together “very quickly.”

Running down the centre of each laboratory is an approximately 8 metre glulam beam spanning from the roof ridge to the chimneys, supporting the unusual roof form. In other locations, the material is used to make the openings for doorways and fenestration. In order to keep the CLT “visually consistent with the rest of the job,” says Vowels, “we worked with the engineers to keep the beams’ ‘grain’ in the same direction as everywhere else (i.e. vertical) – this created a slightly deeper beam, but was more visually appropriate.”

The building’s sustainability strategy is predicated on a “very simple method of operation and a ‘use less’ mantra,” says Vowels, with high insulation levels, natural daylight levels through high performance glazing, and passive ventilation. The client’s brief was to avoid a complex Building Management System; instead there are horizontal brise soleil on the south elevation (and vertical on the west), to provide the appropriate shading relative to the position of the sun.

The project’s architect reports that Design Engine Architects has had “very good feedback” from the head of science on the building now it’s in use, “both as a piece of architecture and more importantly, what it’s like to teach in.” Having gone from rooms in 19th century buildings “which are a little tired,” the larger, hybrid labs in this building were “more of an evolution than a revolution,” but exactly what the school required to further its science education.

As a project which went on the back burner for several years, it’s a strong testimony to the relationship between architect and client that the new STEM centre stands as a design that’s faithful to its creators’ original intent. It’s also a refreshing counterpoint to historic architecture which complements but elevates its surroundings, without being ostentatious, and creates a great new circulation space for a famous school, and its scientists of the future.