What we know about plans for the UK's tallest building, 1 Undershaft

Revised designs for the UK's joint-tallest building have put the 309.7m (1,016ft) skyscraper named 1 Undershaft back into the headlines this week.

The path towards the construction of the 74-storey tower in the heart of London has been beset by controversy and the latest proposals have continued to attract detractors.

Located in the City of London, the towering skyscraper is set to be the same height as The Shard, which also dominates the skyline in the capital.

However, the latest proposals for a 7m-high digital screen in St Helen’s Square at the base of the structure have come under fire, with critics saying it will create an “environment of surveillance” due to the increased security measures to combat vandalism.

Here’s what we know – and don’t know – about the plans for 1 Undershaft…

What we know

The 1 Undershaft skyscraper has been designed by Eric Parry Architects to replace St Helen’s Tower.

The building was approved to be built in 2016, with the initial height of 1,000ft (304.8m) being increased to 1,016ft – making it the same height as The Shard, currently the UK’s tallest building.

The structure will be positioned near prominent landmarks such as the Leadenhall Building and The Gherkin.

Architects' Journal reported last year that the construction of 1 Undershaft would take around five years. The tower is scheduled to be finished in 2029, subject to its new design being approved.

The development is primarily focused on office space, but it will also include retail units and public areas, as well as a restaurant and cultural spaces on the 10th floor. Plans also include a publicly accessible viewing gallery offering panoramic views of the city and educational galleries to be curated by the Museum of London.

The City of London Corporation must give planning permission for the building to be built and construction is due to take around five years.

The latest proposals for the 74-storey skyscraper include a 7m-high digital screen at the base of the building showing information on sports fixtures and concerts.

What we don’t know

While the project has made significant strides, several key details are still unclear.

While the design and purpose of the tower have been revealed, it is not yet known exactly what types of businesses or tenants will occupy the office spaces.

Specifics about the retail and public amenities on offer remain vague, and it is still uncertain how much of the building will be open to the public beyond the viewing gallery.

Additionally, while sustainability is a core element of the design, exact details on the green technologies being implemented have not yet been fully disclosed.

While the tower is expected to be a major landmark, it’s unclear how the building will impact the surrounding area in terms of traffic, infrastructure, or the overall aesthetic of the City of London.

We also do not know if the most recent plans will be passed – meaning the final design is still not yet certain.

It has been reported that the building is due to open in 2029 – but ongoing delays mean we still do not know if it will open its doors in this decade.

Where are the tallest buildings in the UK?

The 10 tallest buildings in the UK are all located in London.

The UK's highest tower, The Shard – and tallest building in western Europe (Russia's Lakhta Centre in St Petersburg is the tallest in Europe overall) – looms over the capital at a mighty 309.6m (1015.7ft) tall.

The tallest building in the UK outside London is Manchester's Deansgate Tower South, standing at 201m high. Plans have been revealed, however, for a new skyscraper in Manchester, Viadux 2, which would stand at 241m when finished, making it the third tallest building in Britain.

Britain's biggest skyscrapers, however, dwarf in comparison the highest towers globally. Dubai's Burj Khalifa remains the tallest building in the world at a staggering 828m tall – more than 500m higher than The Shard.

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