July 20, 2020
Cantillon undertook the structural stabilisation, basement deepening & superstructure packages to the existing Georgian brick buildings at 5-15 Sun Street Terraces on behalf of Alloy MTD. The terraces had remained empty & for over 30 years had fallen into a state of significant structural disrepair. The neighbouring Flying Horse public house remained trading throughout all project works. Cantillon delivered the package of works to retain, repair, stabilise & reconfigure the terrace for its inclusion within the new development of a boutique hotel, to be known as ‘Ardeir London’.
From the outset, there were several major constraints with further complex requirements, and their associated risks, added post contract award. All of these required the utmost attention in an iterative temporary and permanent design management processes with client professional team and our supply chains. Key milestone target dates for the various design stages, fabrication & delivery to site were identified and agreed upon.
To enable effective clearance & deliveries by agreement with the City of London, Cantillon created a pit-lane outside 5-15 Sun Street. 97% of all materials removed from the site were diverted away from landfill despite the logistical & spatial constraints.
Several attempts to stabilise the building and support failing floors had occurred prior to Cantillon taking possession of the site however, extent and condition of existing supporting temporary works was extremely limited. As safe routes and exclusion zones were created, Cantillon’s engineering team assessed the structure & designed a robust temporary works scheme to provide the structural stability & access required to progress the permanent works.
This included phased internal strip out and construction of primary steel beamed flooring with secondary timber joists / external strengthening repair works to facades utilising grouted helical bar within mortar beds and sympathetically coloured lime mortar to finish, new lintels, using reclaimed stock bricks to rebuild whole portions of walls and flat brick arches plus Portland Stone windowsills matching strict conservation requirements. All installed with rigorous inspection regimes and from a fully enveloping scaffold that didn’t crush or pull apart the fragile terrace buildings.
Having stabilised the structure & stripped the internal areas while retaining the shell, masonry strength testing revealed further stiffening was needed.
The client took this opportunity to radically alter the internal layout of the terraces, which we undertook in collaboration with the project engineer AKT II to ensure careful structural assessment, programming and execution of works, especially with the neighbouring One Crown Place development being tight to our building fabric requiring further amendments to our external scaffolding temporary works schemes.
Works associated with internal steel structure stiffening within the shell of the old buildings were co-ordinated with MOLA watching brief within the deepened basements. 21m deep mini piling approach with respective pile caps to support new steel framing was best suited inside 3 properties & underpinning to the remaining 3 houses when the basement level was lowered more extensively.
Floor amendments to incorporate new staircase openings & lift shaft followed new basement sewer heading & drainage, RC slab construction in all 6 basements, waterproofing & blockwork walls. New timber floors were provided throughout the terrace.
The project team ran two phases of work concurrently & operated next to the One Crown Place site. Combined logistics, planning & co-ordination was imperative as space was of a premium. Occasionally, shared opportunities presented themselves benefiting both contractors.
At the completion of our works the site was handed back to the client for their internal fit out & roofing contractor.