Principal Tower

Principal Tower on the right, seen from Bishopsgate.

[edit] Introduction

Located at Principal Place in Shoreditch, on the edge of the city of London, Principal Tower was completed in November 2019. It was designed by architect Foster and Partners as one component of a mixed-use scheme. With a total of 298 apartments, the 175m-high, 50-storey tower is also one of the tallest residential buildings in London. It provides residents with shared amenities which include a grand lobby with 7t staircase, a half-acre piazza with boutiques, swimming pool, spa, gym, cinema and residents’ lounge. Also forming part of the development is a 15-storey office building occupied by Amazon UK.

Principal Tower comprises three different-sized volumes massed together to form a cruciform plan. Two lower height forms flank a taller central volume which is topped by a duplex penthouse. The building’s cruciform plan – which fits into a 25m x 25m square – maximises the perimeter and provides eight external corners which allow each apartment to have more glazing and its own quadrant-shaped balcony; furthermore, the curved glass provides multi-directional views over London.

On a typical floor there are eight apartments: four two-bed and four one-bed. Layouts maximise the living area while the entrance is central and arranged to eliminate unnecessary circulation space.

The building has a distinctive Art Deco feel, with its verticality balanced by strong horizontal lines of the bronze-coloured louvres which curve gracefully around corners and break-up the apartments’ floor-to-ceiling glazing. This does not apply to bedrooms which are clad with opaque, ribbed metal cladding panels.

[edit] Constraints

Despite its capacity and height, Principal Tower has a compact footprint which was determined by numerous site constraints. The most restrictive of these was the Victorian railway infrastructure which threatened to impact the south-east corner of the site – critically important as this is the location of the front entrance both to the tower and the commercial component of the development.

Thanks to an air rights agreement with the local authority and an opportunity to work through a period when no trains were running, engineer WSP was able to quickly deck over the rail cutting with a steel and concrete pedestrian plaza.

Another constraint was an existing bridge abutment which required coring through to allow the installation of piles during a window of opportunity just prior to the 2012 London Olympics.

Further site constraints added to the complexity of the architectural and engineering solutions and included siting the building so as not to encroach on the viewing corridor from Westminster Pier to St Paul’s Cathedral. This forced positioning the building towards the railway and over another constraint – a protected future rail corridor for two additional lines. Accommodating this required very deep piles for the tower’s substructure in close proximity to the railway, as well as the construction of a heavy structure spanning across the rail corridor.

[edit] Project info

• Area 34,900m2
• Height 175m
• Architect Foster & Partners
• Structural engineer WSP
• QS Gardiner & Theobald

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