Hybrid Steel and CLT Design for 38 Berkeley Square in London

The 38 Berkeley Square development in London's Mayfair is an 11-storey commercial project delivering over 7,890 m2 of office accommodation and 650 m2 of communal terraces. Designed by Piercy & Co with Elliott Wood as structural engineer and Mace as main contractor, the building utilized an exposed cross-laminated timber (CLT) flooring system supported by a structural steel frame. By reducing structural weight and transferred loads, the project used a raft foundation instead of traditional deep piles, halving the below-ground concrete volume and reducing the schedule. Analytical modeling addressed fire safety and self-extinction of exposed timber interfaces to meet regulations without full-scale destructive testing, while just-in-time steel deliveries accommodated tight urban site constraints.

Key takeaways

• A hybrid structure combining steel framing with exposed CLT floor panels reduced foundation loads, allowing a raft foundation that halved subterranean concrete volume compared to deep piles.
• Bespoke connections were engineered between steel beams and CLT panels, incorporating over-boarded interfaces to manage heat transfer and ensure fire compartmentation.
• Analytical modeling proved the fire performance and self-extinction of exposed timber interfaces, securing regulatory approvals without requiring full-scale physical fire testing.
• Strict site constraints in central London were managed using just-in-time deliveries and sequential floor erection as temporary lay-down areas, with 99% of structural steel sourced under BES 6001.