Capital Square, Edinburgh

Out with the old, in with the new

Capital Square office block, located on the site of the Sky Park building at 62 Morrison Street, Edinburgh, was designed by engineers Blyth & Blyth as part of the Edinburgh One office development. Sky Park, a former automated parking garage, was demolished to make way for the development. The project consists of a 2 – 3 level concrete basement which provides onsite parking and provision for plant space.

The basement was constructed in close proximity to surrounding structures. Excavations adjacent to Edinburgh One were enabled through the use of large-diameter contiguous piles. The 122,500 square ft of office accommodation is provided over levels 00 – 07. Level 00 is a suspended concrete flat slab construction accommodating the main, double-volume entrance and external landscaped gardens for tenants.

The key challenges were the demolition and construction of the multi-level basement directly adjacent to The Edinburgh One site.  This required the use of a contiguous piled wall, constructed at the interface, to provide lateral support for the excavation of the basement and the installation of the North Core Foundations.

The excavation of the basement was achieved with king post walls on three boundaries.  The king post walls were propped at mid-height by flying shores spanning the width of the basement to enable the construction of the foundations, ground slab and the first suspended slab.  The temporary flying shores were removed once the suspended slab linked the north and South cores. The perimeter concrete walls and ground slab for the basement are constructed with a waterproofing additive, PUDLO, to limit the time required for external tanking allowing the contractor to cast the singe-sided walls against the temporary king post wall.

Site access was constrained on all sides and construction required careful co-ordination and consideration for access and the adjacent landowners and users.

Waterproofing

Architect Steven Millford of Hurd Rolland Architects specified PUDLO for this standard two-storey underground basement.

A straightforward waterproofing application, PUDLO CWP (2,000 cubic metres) was used with work beginning in Jan 2018 and finished Sept 2019. Just one pour is left to complete in addition to crane infills.

Brett Steyn, Director of Blyth & Blyth said, “PUDLO was used to achieve the waterproofing requirements for the basement slab and perimeter retaining walls. Their team provided technical support to the specifying architect and the design team in the production of standard interfaces and the reinforcement and construction details. Their site team were professional and proactive in the application on site.”

PUDLO’s site operative Brett Hattle said, “Careys were very easy to work with, especially James Purves, Carey’s Project Manager.

The project went like a dream despite a lot of cold and rain that you’d expect for Scotland.”