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St. James Sq
Cityzen were employed to be the Contractors Designer for
their CDP items of the Facade Performance and Lead work

Architectural Detailing


Blou construction , Propak, Edmonds, ADS Joinery, Paye Stone, Richardon's Roofing

Total build cost

£ >20m

We worked with our clients 21Construction to deliver the thermal, airtightness and leadwork design packages on this project in St James Square, London, which involved the retention of the listed façade and complete demolition and  redevelopment of the internal structure to provide new commercial and office space.

as part of their construction works we were employed to develop the overarching architects works as part of the Contractors Design Portion for the Thermal envelope, including detailing of the walls to provide an insulated  and air tight box to meet building regulations, this work included, coordination with the existing historic fabric, meeting the needs of the structure which had already been inserted into the building prior to our appointment and ensuring that the fire stopping was feasible within the spaces allocated. within this work we also undertook interstitial condensation and U-Value calculations to ensure the building performance was met as part of the final SBEM calculations.

Coordination of the thermal and airtightness detailing with fire, structure, retained façade and the original architects design intent  around the doors and windows, floors and ceilings was complex, but a worthwhile and rewarding challenge which enable the architects vision and the buildings history to both be intact.

Additional Images of the finished building can be found here: