Repairing an Icon

The Grade II*- listed Battersea Power Station has been sympathetically transformed into a vibrant twenty first century destination as part of a £9 billion, 42-acre regeneration of this former brownfield site. In this article, we look more closely at some of the challenges the team faced around repairing the existing fabric of the structure and recreating the iconic, but crumbling, chimneys with four perfect replicas.

Given the scale and condition of the existing Battersea Power Station building, approaching the repairs to the external fabric was a major challenge before a full retrofit and redevelopment could take place. Buro Happold finalised a strategy that involved removing damaged brickwork to access sections of the steel frame, which were then grit blasted and repainted. With a risk-based approach, a key aspect was balancing optimised intervention with reuse and whole-life design.

One-and-three-quarter million replacement bricks have been specially made to match the original. Our experts devised a considered justification and repair strategy for the existing steel frame and the brickwork facade based on a risk approach to find the right balance between the initial capital expenditure and an ongoing maintenance regime. We demonstrated compliance for the new loads and disproportionate collapse requirements, while limiting the amount of overall strengthening needed to only a handful of places.

Renowned for its four, instantly recognisable towering chimneys, Battersea Power Station is an industrial icon that occupies a unique place in the public consciousness. Image: Buro Happold.

The structure itself is not simply composed of brick, it’s a steel building clad in brick, and parts are over 90 years old. As the steel frame has moved over the years, the brick has cracked allowing water to seep in and further warp the steelwork. We had to come up with a sensitive repair strategy to ensure the safety of the complex. Our approach involved taking down the historic brickwork, painting the steel with a protective coating and reassembling the bricks. After scouring the archives, our team was even able to source additional bricks from the original brickyard.

Original slot windows on the sides of the building were extended in height to increase the access to daylight in the new residential units. This involved removing and retaining the historic bricks for reuse where possible, and installing new steel framework around the windows.

To maximise preservation of the existing fabric of the power station, we extensively re-used existing steel columns by connecting new floors to them. We developed a set of simple and cost-effective details using bolted connections, by replacing existing rivets with bolts and using shimming plates. We developed a highly innovative four-step approach to check the existing column capacity, and reduced existing column strengthening from 25% to 5% of members.

The existing southern facade of the Boiler House required new restraint to stabilise and preserve it, replacing temporary works from the 1990s. This was done with elegantly designed bowstring trusses, meeting the client’s desire to create a large, open space, and spanning 25m with minimal impact on the existing fabric.

We devised a sensitive repair strategy to ensure the safety of the complex including the power station’s historic chimneys, each of which is unique in its height, geometry and decorative detail. Image: Buro Happold.

Sitting right on the Thames, stability and conservation of the river wall was a key challenge. We took ownership of the condition of the river wall and developed a strategy to raise its level by 600mm to resist 2100 flood levels. The wall condition was extensively surveyed and monitored to inform our repair strategy.

Addressing the chimneys, we established and led a conservation steering group to explore practical options. When it became apparent that these monoliths were beyond safe repair, the decision was made to dismantle them and create new geometric replicas on site around new stronger internal steel frameworks. Requiring 600 tonnes – or 25,000 wheelbarrow loads – of concrete and 1,500 litres of paint to implement, this method upholds the very highest safety standards while maintaining the building’s famed silhouette in fine detail.

When it became apparent that these monoliths were beyond safe repair, the decision was made to dismantle them and create new geometric replicas on site. This required Requiring 600 tonnes – or 25,000 wheelbarrow loads – of concrete and 1,500 litres of paint to implement. Image: Buro Happold.

The team decided to take a stepped approach to the rebuild. Work began on the south-west chimney and it was only once it had been successfully reconstructed to a height of 25m, that work commenced on the three remaining chimneys. The sequencing schedule was also important given the iconic nature of the building’s profile. We didn’t want the structure devoid of chimneys on the London skyline at any time.

To dismantle the chimneys, our experts used a circular rigging solution, descending the chimney slowly from the top, to allow the team to chip away at the material and safely remove the debris through a funnelled chute that ran through the centre of each chimney.

Image: Buro Happold.

Reconstruction could then begin. Although each chimney is visually identical to the original, they now have a more secure, modern pattern of steel reinforcement within the concrete to ensure they better endure the ravages of time and corrosion.

It was of paramount importance that each chimney was an exact copy of the original. Each chimney is unique in its height, geometry and decorative detail. We surveyed each one, creating a 3D digital model to capture its specific features – including the fluting and ornate detail – ensuring it could be rebuilt exactly as it would have been originally constructed. Paint scrapings were also carefully scrutinised, and matched with new paint to make certain the new chimneys were accurately replicated.