Tisserin was brought into the GSK development to elevate the roof design and create a visually striking architectural feature. After exploring several geometric concepts, the design team selected a timber diagrid roof as the optimal solution—combining aesthetic impact with structural efficiency. Tisserin’s role was to develop and deliver the scheme.

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Achieving a consistent and seamless roof grid was essential, as the diagrid forms a key visual component of the building’s interior. The spacing and alignment were carefully set out so that the atrium ceiling elegantly frames the diagrid, with nodes positioned precisely where they meet the atrium walls.

The timber diagrid spans large areas without internal columns and maintains a uniform structural depth. Some roof sections cantilever beyond the perimeter walls, requiring careful consideration of timber durability in external environments.

With its twoway cantilevering geometry, the structure required extensive research and modelling to determine the most efficient and resilient design. Durability considerations were integrated from the earliest stages, ensuring long-term performance of timber elements inside and outside the building.

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Purpose and unique aspects

The GSK Reception building is a two-storey cross-laminated timber (CLT) structure featuring a composite timber diagrid roof panel. This design creates a visually striking reception and office space while prioritising sustainability and architectural elegance. The roof spans approximately 100 sqm, using a hardwood Glulam diagrid for structural efficiency and aesthetic appeal.  

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Brief and challenges

The client requested an upgrade from a standard roof design to a visually interesting geometry. Tisserin proposed and delivered a timber diagrid roof, ensuring:

• Seamless alignment of the roof grid for visual impact.

• Integration of cantilevered sections beyond perimeter walls, requiring advanced detailing for durability in external conditions.

• Efficient geometry to maintain consistent roof depth without internal columns.  

Key technical objectives

• Long-span cantilevers in two directions, creating a double cantilever over the front.

• Bi-directional moment connections at beam-to-beam nodes.

• Use of birch glulam, a species not governed by Eurocodes, assessed for humidity and external exposure.

• Composite action between glulam beams and CLT slabs, achieved via diagonal screws.

• Concealed joints for exposed timber aesthetics and fire-rated performance.

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Fabrication and detailing

• Bespoke fabrication of glulam and CLT elements.

• Special attention to durability and detailing for external timber.

• Fire-rated exposed timber solutions integrated into the design.  

Why it stands out

This project exemplifies advanced timber engineering, combining sustainability, structural innovation, and architectural beauty. It required rigorous analysis of cantilever behaviour, wind load stability, and composite action, as reflected in internal calculation packs and design discussions.