Refurbishment of a Commercial Building with Single Level Basement and PiledFoundations for a 70% Increase in Floor Area and Structural Carbon Rating Scheme (SCORS) "A".Â-Paper

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1 Triton Square, a six-storey commercial building with a single basement near Euston, London, was refurbished to add three storeys and infill much of its central atrium. The changes increased floor area by about 70%—approximately 13,000 m²—while preserving the basement’s headroom and plant facilities.<br /><br />The added loads exceeded the capacity of many existing foundations. Rather than replace them, the team reused the original large-diameter London Clay piles and strengthened them with 188 small-diameter bored piles and a slender, 650 mm-thick piled raft. Local pile caps and a thicker raft were used where needed. Detailed original construction records, targeted investigations, pile-test data and three-dimensional numerical analysis informed the design. Construction monitoring confirmed that movements were consistent with predictions.<br /><br />The project retained a high proportion of the existing structure: approximately 35,000 tonnes of concrete and 1,900 tonnes of steel, including reinforcement, were reused. New concrete mixes also incorporated substantial cement replacement. The refurbished building’s structural embodied carbon averaged 136 kgCO₂e/m², earning a Structural Carbon Rating Scheme “A” rating and comparing favourably with the cited new-build design target of 350 kgCO₂e/m². The project demonstrates how foundation reuse and carefully engineered strengthening can enable substantial expansion while reducing material use and embodied carbon.

Keywords

Triton Square

Euston London

commercial building refurbishment

foundation reuse

piled raft foundation

London Clay piles

structural strengthening

embodied carbon reduction

sustainable retrofit

structural carbon rating