Amin Taha and Jason Coe explain the guiding principles behind the practice’s often innovative and always expressive use of materials.
Jason Coe (left) and Amin Taha pictured in Groupwork’s purpose-designed London studio. Credit Agnese Sanvito and Timothy Soar
Groupwork is a London-based employee ownership trust chaired by architect and founder Amin Taha. Established in 2003, the award-winning practice has made a name for itself through a series of visually striking, progressive and at times architecturally daring works.
Material expression and rigour are central to its approach with notable projects featuring cast, terracotta-coloured concrete (159-168 Upper Street), open-bonded brickwork with an exposed CLT superstructure (Barretts Grove), and stone exoskeletons (15a Clerkenwell Close and 317 Finchley Road) to name but a few.
So how does the practice research and specify materials? What inspires it? And how does its extensive library resource contribute to the processes of designing and making? Amin Taha and project architect Jason Coe explain.
How would you define the practice’s overall approach to materiality and material selection?
Amin Taha On the whole, I would say tectonic in the [Gottried] Semper and [Edward R] Ford sense. That is, ‘articulating’ the ‘joining and binding’ to ‘complete’ a set of details that are emblematic of a specific design, while allowing others, such as door handles, to be ‘autonomous’. For us, there are no illegitimate materials so we would consider any; it’s how and to what end they are used. As Ford suggests, it’s the ‘intent’ that might be inherently flawed.
We were recently at Coventry Cathedral discussing Ove Arup’s aisle column design, which was originally intended to terminate above floor level on a solid glass sphere. For us, the solution was both structurally appropriate in compression, and poetic in its post-war, existential narrative of all that is solid melting into air.
Yet architect and client – presumably short of understanding the structural properties of solid glass – opted for metal pegs, which while also appearing impossibly light are nevertheless a critically different word in the prose.
Luget limestone from Carri re de Luget. “Quarried in westernFrance, this high-quality limestone incorporates beautiful orangey brown hues. We are using extremely large blocks of it with a hewn textured finish to form the load-bearing walls of our House in Ancient Woodland. The stone is also being used to form expressed, post-tensioned floor slabs that span the entire living space.”
How is the materials library organised and how does it function within the practice?
Amin Taha The library is for everyone in the office, as well as other architects, engineers and students. All visitors are welcome; but you have to remember that it’s a reference resource not a lending one!
The library itself is arranged across half-a-dozen shelves as well as the floor and office garden. The shelves contain physical samples, including stone, glass, metal (in various finishes), timber (for structure and cabinetry), as well as one or two door handles and locking mechanisms we’ve designed and built with specialist metalworkers.
Next to these are a mixture of brochures and books covering technical details, basic building technologies, detail precedents, as well as the structural and aesthetic qualities of materials. Written works by Ford, Semper and [Kenneth] Frampton sit alongside these, reminding us that the etymology of architecture is tectonic with its details intrinsic to the process that forms the product. In other words, you don’t go to the library with a fixed image in mind first and hope the materials, products and details will suit!
Jason Coe Aside from the shelving, the studio floor contains 1:1 fabricated samples and prototypes of buildings we have worked on, or are still working on. These include wall and floor build-ups and intersections, as well as perforated or solid brass facades. There are also scale models of various schemes and research projects we’ve undertaken, such as the stone tower for the Building Centre’s ‘New Stone Age’ exhibition.
The garden houses a number of stone samples left out for weathering and dirt/ moss gathering purposes. It also contains 1:1 superstructure prototypes for similar reasons. These include a full stone exoskeletal of basalt and a scarf-jointed timber and stone composite column base.
Everyone is responsible for calling in samples when they’re needed and keeping them if they’re of use on one or more projects. While most large samples are born in the specialist subcontractor’s workshop and stay on site as a control item, some of them still make their way back to the studio…
Cross laminated stone from Ateliers Romeo. “Developed in conjunction with stonemason Ateliers Romeo, this innovative and ecologically-sound product is made up of waste sheets of stone bonded together with thin layers of resin. It’s not only strong but can be manipulated into unusual forms. We’ve used the material several times, most recently to form an architectural installation at the 2021 Seoul Biennale.”
How do you research new materials and what have you discovered recently that interests you?
Jason Coe It should go without saying that whatever material we’re looking at will have to be handled, assembled, and installed by someone, so why not start there? Our approach is to visit specialist subcontractors’ workshops with the aim of discussing our ideas, explaining how details might work, and learning how they could be better done. This enables us to develop better details, use something that’s tried and tested, or invent a solution that neither us nor the subcontractor would have come up with alone.
In terms of recent discoveries, we are particularly interested in dowel laminated timber (DLT), which is essentially a cross laminated timber (CLT) but without the glue. The moisture differential between the air-dried hardwood pegs and softwood planks swells the former, tightening the grip and making the whole strong with an even lower embodied carbon than CLT
We’ve also been looking at perforated metal and chainmail cladding where rainscreen metal facades are required on tall structures for reasons of fire performance, screening retrofitted external insulation, privacy, security and sunshading. These types of materials can reduce the quantity of metal used by varying degrees from 40-80 per cent.
At what point in the process do materials become a focus and how important is contextuality in terms of final selection?
Amin Taha I would say that all aspects of the project orbit our minds and feed back into each other throughout design development, the ‘better’ or ‘appropriate’ prose having to crystallise according to whatever programme we agree with our client. Numerous material ideas will be considered, swapped, influenced, and weighed against tectonic abilities, embodied carbon, and specificity to the immediate social history.
Do you find yourself returning to certain materials, and if so which ones and why?
Amin Taha Without fail we use concrete, steel and glass on every project, diminishing their quantity by substituting them where possible with timber and stone. Brass andbronze are frequently favoured for their longevity and changing appearance with tactile use.
Perforated metal is fun for being an economic and lower embodied carbon ‘sleight of hand’ where you’ve been driven to use conventional solid metal rainscreens. The larger the perforation or weave, the smaller the quantity of metal used, the greater the transparency, and the higher the number of uses and meanings. What is a perforated or woven metal but a gossamer veil? What is hiding behind dictating the form? Is it solid or air? From a distance long established, when close impermanent? Yet at the same time, it’s pragmatically protective of the fabric behind, aiding privacy and lowering solar gain.
Is there a material you would like to use but haven’t been able to yet?
Amin Taha Yes, glass spheres at the base of vast columns!
Coloured and textured cast glass from Glashütte Lamberts. “We are planning to integrate this beautiful, tinted and textured cast glass into the rooflights of our House in Ancient Woodland project, which is currently on site. The intention is to produce a diffuse, dappled yellow light effect that will visually warm the entrance sequence. The sand-cast glass sample (darker yellow) has a more uneven, handmade appearance with bubbles and other ‘impurities’ trapped within its surface.”
How do you combat waste?
Amin Taha By trying to design buildings that are irreducible. Architects are frequently subject to ‘value engineering’ exercises, where to save money the QS might, for example, suggest removing 25 per cent of the ‘over detailed architecture’ but of course not 25 per cent of the structural columns and beams, nor removing 25 per cent of the heating and water supply. So why not design the architecture so that structure and environmental control are integral?
At Clerkenwell Close, Upper Street or Barrett’s Grove where superstructure is a combination of a thermal and weathering envelope, internal and/or external finishes, a 25 per cent reduction would result in the building falling down! At some point the QS realises the design, costed by real-time suppliers and contractors, is as cheap as it possibly can be for its intent: Barrett’s at 1,850/m2 for low-cost housing, Upper Street at 2,800/m2 for a ‘significant’ corner site in a conservation area, and Clerkenwell at 2,200/m2 for mid-range central London housing. It’s that (Giorgio) Vasari and (Richard) Sennett lesson: you can only improvise and innovate for better purpose once you learn control of your skills. After you invest more than 10,000 hours into honing them – then you can direct them with ethical purpose.
Stone glass from Dag Inter. “These materials combine thin layers of stone laminated with glass and are designed to be backlit. We initially considered using stone glass on the rooflights of the House in Ancient Woodland to reduce solar gain, but felt that it would be overkill in terms of environmental performance. The opaque material produces a warm tactile aesthetic when illuminated from behind.”
Do you review the library regularly and are there some materials that live there permanently?
Jason Coe We try to have a review and clear-out of similar materials and samples every six months. We’ve actually just had one, so the library is looking a little depleted at the moment. In terms of permanent residents, I can think of a 20-year-old CLT sample, a brass window frame with a structurally bonded nylon isolator, a Mies-inspired cruciform column that employs the same nylon isolator for thermal and structural performance, a flint-lock door set, and various types of stone and metals, including perforated, woven and patinated products.
What happens to materials/samples at the end of projects?
Amin Taha Generally, they stay with us, unless we have more than one of the same item. 1:1 prototypes and as-built details also remain in the library as we often need them as ‘proof of concept’. We used one recently to illustrate an idea to a facade consultant – recommended to the client by the contractor and project manager – who wanted to use an established supplier charging around four times the price of what we said it could be done for!
Do you organise factory visits and make use of materials based CPDs?
Amin Taha Yes, factory visits always take place at the outset of the project to learn from makers. Easier and faster processes,
reduced materials, less waste and better outcomes for clients and architecture in general tend to arise when meeting, seeing and debating with those that cut, carve and assemble the materials you’re interested in.
CPDs used to occur regularly before the Covid pandemic. These varied from material suppliers, including stone, glass and timber, to system and solution providers, such as Envirograf, who I would recommend.
