One Undershaft to become the tallest skyscraper in London and the United Kingdom

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One Undershaft is set to share the status of the tallest skyscraper in London and the United Kingdom with The Shard if a request made to update the design and slightly increase the height of the building is approved. The request was submitted to the City of London by the project’s architect Eric Parry Architects.

Founded by Eric Owen Parry RA, a British architect, designer, writer and educator, Eric Parry Architects, is an award-winning global architecture, design, planning and strategic consultancy based in London. Some of the company’s notable schemes include 50 Fenchurch Street, No.1 Grosvenor Square, and One Liverpool Street.

According to the application, Eric Parry Architects seeks to increase the skyscraper’s height from 304.94 meters Above Ordnance Datum (AOD) to 309.6 meters AOD. The term Above Ordnance Datum (AOD) refers to a height above the Ordnance Datum. An ordnance datum (OD) on the other hand is defined as the vertical datum used by an ordnance survey as the basis for deriving altitudes on maps.

This increase in height would make One Undershaft the same height as the Shard, which is the UK’s current tallest building. The height of both buildings is determined by a Civil Aviation Authority safety policy that restricts the height of buildings in central London to 309.6 metres AOD.

In terms of storeys, the new plan proposes an increase of the building’s floors from 73 to 74.

Additional changes meant for the One Undershaft

According to planning documents, along with the increase in height, Eric Parry Architects proposed a change to the shape of the building from a cross-braced and tapered tower to a tower segmented into four vertical blocks. Reportedly, this change will in turn increase the usable floor area by 30%.

As part of the proposed changes, a public roof garden will be added on the 10th floor of the building. The garden will extend over a curved canopy above the corner of Leadenhall Street and St Mary Axe. Additionally, several winter gardens and external office terrace spaces covering an area of up to 1,530 m2 and 1,370 m2 respectively will be added. Furthermore, One Undershaft will get approximately 110,000 m2 of workspace up from 90,000 m2.

According to the One Undershaft development team, the changes to the design have been made to adapt to and respond “to post-pandemic markets and user demands”. The team, in addition to Eric Parry Architects, includes DP9 as the planning consultant, Kanda Consulting as the engagement consultant and Stanhope as the development lead.

SLA and WSP are also a part of the team as landscape architect and multi-disciplinary engineer respectively.

Noteworthy, the building will retain some of its features. For example, according to Eric Parry Architects founder Eric Parry One Undershaft retains the upper floors for educational and public access through a collaboration with the Museum of London.

Development and construction of One Undershaft

Developed by  Aroland Holdings, One Undershaft is set to replace the St Helen’s tower that sits in the heart of the ‘Eastern Cluster’ of the City of London at the junction of St Mary Axe and Leadenhall Street.

Construction is expected to take approximately five years subject to planning, with enabling works starting in 2024. The actual construction work will start in late 2025 after the demolition of St Helen’s tower and be completed 4 years later in 2029.

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