5-7 St Helen’s Place is the new home to the historic Worshipful Company of Leathersellers, a City of London livery company founded by charter in 1444. Leaving their previous premises on the opposite site of the street, the building was reconstructed behind and underneath a 1920s retained façade. As well as new office space to let in six storeys above ground, a new threestorey basement was built to contain a new dining hall and reception room, along with catering and archive facilities.
We provided full structural and civil engineering services for demolition of the existing structure, retention of the existing façade, and construction of the new building.
Key technical challenges
A particular challenge was the construction of the three-storey basement within a relatively small site footprint, constrained by neighbouring buildings on three elevations, including the Grade 1 listed 15th century Great St Helen’s Church. On the fourth elevation, the site was constrained by both the retained façade and by the small private street off Bishopsgate used to access the site – St Helen’s Place.
To maximise the basement extents on this tightly constrained site, it was essential to excavate underneath the retained façade and build out to the kerb-line of the street. We specified an unusual system of temporary works using extensive plunge columns and needle beams, that would support the façade both horizontally and vertically to enable this undermining to take place.
The control of ground movements experience by the church during excavation of the basement was a critical factor to the success of the project. An unusually high stiffness temporary propping system was required to prevent cracking to the masonry building.
The Worshipful Company of Leathersellers
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