When Amin Taha and London practice Groupwork were asked to create 168 Upper Street, the architect wanted to reference the bomb-destroyed 19th century block that once stood on the site. Carefully reconstructing an image of the building from photographs, a computer model was used as the template for the formwork. But not wanting to simply ape the lost building, elements of chance were encouraged, with inaccuracies in the fabrication or casting process left and emphasised by irregular placement of new elements such as windows and pivoting openings – recalling the architectural installations of artists such as Rachel Whiteread and Do Ho Suh.

The hollow terracotta facade was cast in over 300 sections, using robotically routed recycled polystyrene and wooden moulds, that combined with CLT floorplates offers reductions in waste, construction time on site and cost. "The comparable for routing/cutting recycled expanded polystyrene and gluing it to inexpensive plywood or OSB makes for less costly formwork than for instance phenolic plywood used for fair-faced concrete or fabricated timber planks to gain a boardmark effect," explained Taha. 

"The carbon footprint of combining recycled polystyrene with normal plywood or OSB is only around 25% less than making phenolic plywood, better but not a huge amount," he told Domus. "The cost of using the routed polystyrene system as formwork for an insitu twin wall that acts is superstructure, thermal and waterproof envelope as well as internal and external finish is 50% of a steel or concrete frame superstructure, sub-structure to hold up pre-cast panels, weathering and thermal envelope then internal finishes."

CLT floor plates sit in notches in the load-bearing facade structure, creating a shop at street level and three levels of workspaces and apartments above. The floors cut short elements of the mouldings, highlighting the changes between original building and copy. 

“The cast facade bears the mark of the tooling head which traced against theformwork geometry, which can be seen on closer inspection of the facade," says the practice. 

“This digital manufacturing process having as many opportunities for ‘failure’ as the physically manhandling of formwork and pouring the monolithic mix, reinforced the notion of misremembrance intrinsic to the buildings construction and our understanding of the past."