Technical Frame

Twist in the strategy

A conventional plan has been replaced by a cross formation, creating more courtyards. The fl oorplate is then twisted every two storeys, to maximise light, and wrapped in a gridded screen to simplify the street frontage.

in 2012, Hackney mooted a “timber fi rst” policy, although this was later watered down in the face of potential legal threats from the steel and concrete lobby. Nevertheless the decision was made by the developer, Regal Homes, that the tower should be constructed from CLT. In collaboration with CLT contractor B&K

Structures, several options were evaluated in terms of cost, effi ciency and aesthetics, including a pure timber solution with all internal walls of the structure formed in CLT. However, due to the complex form and the extremely thick slabs that would

have been needed to create the cantilevers, this option was abandoned as too heavy and too expensive. After also considering a glulam hybrid, Hawkins\Brown settled on a hybrid of steel and CLT, wrapped around a reinforced concrete core, as the most effi cient solution. The box section columns that make up the building’s steel frame are either 200mm sq or 160mm sq, which are very thin for a 10-storey tower. This is due to the fact that the CLT, which by volume makes up 90% of the building, is still playing a major structural role.

“I don’t see the benefi t of cutting down more trees just to build a pure CLT building” Alex Smith, Hawkins\Brown

“In its current design it wouldn’t stand without the steel or without the CLT,” explains project architect Alex Smith. “The building’s twisting is a key part of its design. Introducing comparatively small amounts of steel to share the load in key locations allowed the complex form to be created in an effi cient way.” Although a pure CLT would arguably be

more sustainable, Smith is pragmatic about adopting a mixed approach to the frame. While appreciating the low carbon benefi ts of CLT, he says: “I don’t see the benefi t of cutting down more trees just

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PHOTOS: TIM CROCKER