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Concealed Crack Stitching at Grade I Listed Somerset House in £9m Refurbishment

Client:	Kings College London
Location:	London
Approved Installer:	Structural Renovations Ltd
Reference No:	PR198

Built in the late 18th century, London's historic Somerset House is a neo-classical Grade 1 listed building constructed in a quadrangle, with four wings surrounding a large courtyard. It faces The Strand on the north side and The River Thames on the south and is currently undergoing a major £9m refurbishment of the east wing, by Wates Construction, ready for occupation by Kings College London. As part of this refit the Helifix Crack Stitching System was used to repair cracked internal cross walls as it offered a non-disruptive and reliable long term solution.

Where the East Wing meets the South (Riverbank) Wing, there had previously been a boathouse adjacent to the ground floor which had provided a 'buttressing' effect. This was removed some years ago, which lead to the cracking of five internal cross walls on the ground and lower ground floors, about 1m from where they meet the 1.2m thick external brick walls.

The project engineers, Ramboll UK (Cambs), decided there was no current movement and, as the walls were stable, a remedial masonry repair and reconnection was required. The Helifix system was specified because all repairs could be undertaken internally, as no external holes were permitted due to the building's Grade I listing, and this proven method of concealed crack stitching would secure the walls and prevent future cracks developing while still allowing natural building movement.

On either side of the 800mm thick cross walls, Helifix Approved Installer, Structural Renovations, bonded 2m long stainless steel HeliBars into channelled-out mortar beds at five different levels, with the ends bonded into 500mm deep angled holes drilled into the external wall. Many of the crack stitches were also drilled and returned into the cross wall where a chimney was present. Following crack repairs, repointing and plastering there was no visible sign of the masonry repairs and strengthening that had been carried out.