Mace Construct completes 30 Duke Street with 78% reused steel and 744 tonnes less embodied carbon

Mace Construct has completed 30 Duke Street St James's in London, turning the former French Railways House and 48-50 Jermyn Street into a 68,000 sq ft fully electric office and retail destination. The project is billed as the UK's largest commercial steel reuse scheme, with more than 78% of structural steel sourced from reclaimed material, including steel recovered from GPE's own portfolio. The circular approach avoids roughly 744 tonnes of embodied carbon, according to the project team. The building also uses Hydro CIRCAL 100R aluminium, a first for UK commercial development, and ORAÉ glass made from 100% recycled content. Reclaimed Portland stone, marble, raised access flooring and the original French Railways House mosaic were retained and reused. The project shows what is possible when embodied carbon is treated as a design constraint from day one. But it also raises questions about how to scale steel reuse across the wider industry, where demolition and new steel remain the default. For anyone tracking low-carbon construction, this is a useful benchmark, not just a one-off.