Battersea Power Station – regeneration of an icon

The landmark Grade II* listed Battersea Power Station (BPS) has been sympathetically transformed from a much-loved industrial relic into a vibrant twenty-first century destination. The visionary redevelopment of the 230 000 m² building was carried out as phase 2 of an eight-phase regeneration of this former 42-acre brownfield site on the banks of the River Thames – the full masterplan is shown in Figure 1.

This paper presents a summary of the work undertaken to bring BPS back to life. Arguably one of the most technically and logistically challenging projects in the industry, the redevelopment was achieved through a series of considered, elegant and buildable solutions to preserve the existing fabric. This has been integrated seamlessly within the new structure to provide this iconic building with a new lease of life.

BPS is situated on the southern bank of the River Thames within the London Borough of Wandsworth. Originally marshland and subsequently a water treatment facility, its transition to a power station commenced in the late 1920s. The London Power Company initiated the construction of BPS as its pioneering large power plant following a 1925 parliamentary decision, garnering significant contemporary attention. Original construction details are well-documented, including noteworthy papers by Bartlett and Cadwell (1935) and Berry and Dean (1935).

The site comprised two distinct stations – station A and station B – built between 1929 and 1955. A central boiler house is catered to each power station, featuring individual Turbine Halls (A and B) and switch houses (west and east), as shown in Figure 2. At both ends of the turbine halls, pioneering gas ‘washing’ towers – the world’s first gas scrubbers – were installed, and these four wash towers provided support for the prominent chimneys.

Station A was completed in 1935, while the northern sector of station B, including the northeast chimney, was concluded in 1955 when BPS achieved full operational status. The UK’s third largest site at that time, BPS supplied 20% of London’s power demand while also supplying district heating for Pimlico on the northern bank of the Thames. At the time, BPS stood as the world’s most thermally efficient power station, embodying several pioneering innovations such as gas scrubbing.

Leonard Pearce, London Power Company's chief engineer, led the design of BPS, with notable contributions from engineers H. N. Allott (until his death in 1929) and T. P. O’Sullivan, as well as architect Theo J. Halliday. Sir Giles Gilbert Scott, a prominent architect, joined the project later to address public concerns, and suggested alterations such as transforming the chimneys to a square brick design akin to Bankside power station (now home to the Tate Modern). A number of Scott’s suggestions emerged too late in the process for implementation, but he was responsible for the design of the external elevations and the distinctive brickwork.

Station A was decommissioned in 1975 and station B was decommissioned in 1983. In 1980, BPS received Grade II listed status. This was upgraded to Grade II* in 2007 – a distinction held by fewer than 6% of listed structures.

The iconic structure and brick fabric proved challenging to repurpose post-decommissioning and BPS evolved into London's most notorious ruin (Figure 3). Buro Happold's involvement dates back to the late 1990s, spanning various ownerships, including the current owners – a consortium of Malaysian shareholders (PNB, Sime Darby Property, S P Setia and the Employees’ Provident Fund).

BPS is a steel-frame building clad in a brick facade. The internal floors were either clay pots spanning between beams in station A or concrete slabs in station B. The cast in situ concrete chimneys sit atop the steel-frame wash towers.

The internal finishes in the turbine halls are generally terracotta faience tiles positioned in front of brickwork. Station A, built in the 1930s, stands as a stunning example of Art Deco grandeur, while the 1940s station B is far more industrial, likely impacted by post-war material shortages. The differences between the two stations extended to all aspects of construction: station A features heavier plated sections and moment frames, whereas station B typically uses braced structural elements – either frames or columns – to reduce the overall steel weight, albeit resulting in fewer open spaces between them.

The foundations of BPS also varied across the site. Station A was generally founded on group concrete piles, while station B was generally supported by large deep pad foundations that were referred to as ‘elephant feet’. The final southeast corner is founded on deeper bored piles.

The ground conditions typically comprise Gravel, overlaying London Clay on top of the Lambeth Group with Thanet Sands at approximately 70 m depth. However, this stretch of the River Thames is geologically notable for drift-filled hollows associated with the periglacial conditions of the last ice age. These features have particularly steep sides and, at Battersea, extend down through the London Clay almost to the Lambeth Group. The drift material in the hollows was found to be predominantly granular with a cohesive component, but the mass stiffness was shown to be similar to that of the London Clay at the same level. The resulting dramatic geological variations presented challenges for the foundation design across much of the footprint of BPS.

When the project team mobilised in 2012, BPS was in a very poor condition. The majority of the central boiler house had been demolished in the 1980s as part of enabling works for previously failed schemes, with various elements of temporary structures installed. A key early design activity involved understanding the history of these works and how they affected the overall condition and behaviour of the structure.

Demolition work had started on a number of other areas, with the west switch house having significant areas of floor removed and steelwork added in the 1990s. The Art Deco Turbine Hall A and Control Room A – the jewels in the heritage crown – remained largely intact along with Control Room B. In areas where the roofs remained in place, the original building fabric was generally in good condition. However, where it had been exposed to the elements for up to 30 years, there was serious steel corrosion and associated damage to masonry encasement. The reinforcement in the concrete chimneys was in especially poor condition and a 30 m exclusion zone was imposed to mitigate the risk of fist-sized lumps of concrete causing harm if they became dislodged. Several steel girders directly below the chimneys showed serious corrosion due to BPS’s exhaust. In one instance, a 7 ft (≈2 m) deep plate girder was so badly damaged that a person could walk through the space where the web should have been.

Planning consent and listed planning consent for the proposed design (shown Figure 4) was granted in 2012. This included several conditions and requirements that mandated preliminary repair works for BPS. Additionally, planning conditions linked to these works were tied to the development of the surrounding phases. These preliminary (repair) works were imposed to safeguard the remaining original building fabric and to prevent a recurrence of the fate of previous failed development attempts in which demolition works were carried out without any subsequent repairs or reconstruction efforts. These works primarily focused on three main elements – the brickwork facades, the wash tower structures and the eminent chimneys.

The vast engineering challenges for this project fell into two broad categories, which will be looked at in turn.

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  Restoration and reuse of the original building fabric (including preliminary works) (Section 7).

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  Main works – the formation of a new structure within the existing, the ‘box-in-box approach’ (Section 8).

A key driver for the project was to maximise the conservation of the original fabric, especially since previous failed regeneration attempts had included significant elements of demolition. This encompassed repair and remediation works to address years of exposure, along with interventions to give the building a new lease of life and to ensure safety for future generations. These interventions included repairing the existing fabric, installing new windows, justifying new loads and implementing upgrades to meet modern code requirements.

Reuse of the existing structures (foundations, columns, beams and slabs) ultimately led to a reuse of more than 36 000 t of legacy carbon dioxide equivalent. Refurbishment of the masonry for the external elevations led to an additional saving around 4000 t legacy carbon dioxide equivalent, with the internal brickwork saving a further similar amount. Together, these amounts account for around 20% of the total embodied carbon dioxide in the structure.

The reinforced concrete chimneys typically consisted of a 6″ (150 mm) concrete windshield with a 2″ (50 mm) protective tile on the inside face, reducing to a concrete thickness of 4″ (100 mm) at the very highest section. When the current owners occupied the site, the chimneys were showing serious signs of distress, with many large cracks, loose concrete and corroded reinforcement. In the early 2000s, a Conservation Steering Committee was formed to determine the best way to address the key heritage features of BPS. This committee included the London Borough of Wandsworth, Historic England (formerly English Heritage), Buro Happold, BPSDC and a number of trade contractors and other specialists. This forum allowed for the exploration and evaluation of all conservation options prior to agreement on approach. In 2005, Historic England and London Borough of Wandsworth announced that the chimneys would be dismantled and replaced like-for-like.

The concrete chimneys were approximately 50 m tall above the 50 m wash towers. Careful dismantling using hand tools allowed debris to be removed safely by chutes through the chimneys and wash towers to ground level. The reconstruction of exact replicas (Figures 5 and 6) involved 4 ft (1.2 m) jump-form lifts to match the original construction joints, with the concrete placed using wheelbarrows taken up using a service hoist. The chimneys all vary in height to match the originals, with approximately 300 mm between the tallest and shortest. The new 8″ (200 mm) concrete walls are thicker than the original concrete profile due to fire requirements, however match the original overall chimney thickness because acid-resistant tiling was not required. The contract for these works was placed in September 2014 and the work was completed in 2017.

The reconstructed chimneys (Figure 7) have functional requirements as part of the new scheme, with the concrete windshield of the northeast and southwest chimneys containing flues from the two site-wide energy centres. A photo of one of the original chimneys is shown in Figure 8. The northwest chimney is now home to Lift 109, a unique glass elevator experience which transports visitors 109 m to the top of the chimney, offering 360° views of the London skyline (Figure 9).

BPS has been home to a pair of peregrine falcons since 2000. During the construction works, a temporary nest tower was built for the birds, who thrived with more than 30 chicks fledged over the 10-year period. In 2022, the peregrine falcons moved into their new home within BPS’s northeast wash tower.

Although generally in relatively good condition, there were a number of areas where the original external brickwork had suffered damage and needed significant repairs. Alongside this, several existing window openings had to be extended and new openings formed. These included reopening some original areas that had been infilled during the operational life of the building.

The original building was built in three stages and there are three distinct brick pattens, or blends, of individual bricks, which were provided by two separate brickmakers, Northcot Bricks in Gloucestershire and Blockleys in Shropshire. These brickmakers are still in business, and they provided over 1.75 million new bricks, a significant number of which were manufactured by hand to match the original methods. In total, 18 individual brick types were used in unique sizes to achieve seamless repairs, preservation and celebration of the streamlined aesthetic of this celebrated London landmark.

The original brickwork for the elevations was a solid 1.5 brick thick (≈ 350 mm) construction, which was constructed without movement joints. Given the building is approximately 150 m × 150 m on plan, this would be unthinkable to modern standards and led to several issues such as major cracks developing around corners and water ingress affecting steelwork.

Extending the windows in the western and eastern walls involved cutting the original steelwork and installing new steelwork, which required considered works sequencing. Parts of the permanent steel were used as temporary works to save on carbon dioxide and simplify the installation. Modification to the brickwork included incorporating ventilation into the reveals of the new windows of the residential apartments, which required local reduction to a half brick thickness (≈100 mm). The original brickwork was exposed within the residential apartments with no modern materials added to improve insulation properties. After careful consideration, it was decided not to introduce movement joints in the existing masonry fabric, but instead to strategically reinforce the brickwork in key locations to deal with the stress peaks and prevent new cracking. All of these interventions required careful justification to ensure the building complied with modern standards while respecting the Grade II* listed status. The final design is shown Figure 10.

A risk-based approach was devised for the brickwork repairs to minimise the impact on the original fabric. Interventions were only undertaken where there were visible signs of distress, in high-level areas where regular future access would be difficult and above areas with high public footfalls. This strategy was developed to balance capital against operational expenditure, future safe maintenance of the asset, heritage restoration and the risk profile of unrepaired original fabric. This was done in conjunction with all key stakeholders of the Conservation Steering Committee.

Redevelopment of the BPS building required the reintegration of large sections of the original, potentially fragile, structure which in turn meant that the existing foundations had to be reused. The reused elements included large deep pads, precast and bored piles, and masonry retaining walls. The overall foundation scheme was developed to address the challenges of safely and effectively repurposing the structure. New piles and retaining walls were installed in and around the building, but a significant proportion of the original foundation elements was reused.

It is important to note that BPS’s foundations largely predated the establishment of geotechnical design principles, so significant analytical work was required to justify the new loadings. The design of the new superstructure involved both load increases and reductions. Particular care was needed to limit load increases to within the allowable capacities evaluated for the various foundations and to ensure that stability was not compromised through load reductions.

Reused foundations were necessarily analysed on a case-by-case basis, taking account of the specific aspects for each. For example, although there was minimal load change on the relatively shallow wash tower foundations, deep basements were to be excavated immediately alongside at both ends of BPS. These had the potential to compromise the stability of the wash tower. The calculated lateral and vertical displacements exceeded the desired range, but sensitivity analyses were carried out and the impact of the relative displacements was evaluated as acceptable with contingency measures. Monitoring instrumentation was installed throughout the structure, allowing real-time movement monitoring. This was continuously assessed and, with smaller than predicted displacements, the works progressed with confidence.

The client had an extensive drawing archive for the building. The records provided good general information on construction intent but there were very few as-built records. To validate foundation reuse, a succession of intrusive and non-intrusive investigations was carried out to assess all aspects of the foundations alongside the ground investigations.

Investigation works for the piled foundations focused on the following four aspects.

• (a)

  Geometric validation of dimensions and precise locations of existing elements. Dimensional assessments were made on a selection of foundations to ensure a representative assessment was carried out. Similarly, checks were carried out on pile groups to establish cap depth and the numbers of piles to confirm that they conformed with the existing records.

• (b)

  Long-term durability of materials and corrosion risk associated with aggressive ground/groundwater. Concrete cores were taken to assess both physical and chemical properties of the existing piles, pile caps and pad foundations. Chemical tests focused on an overall composition of the concrete and physical testing was used to determine strength, density and the degree of any carbonation. Strength testing on cores from the piles established an equivalent concrete grade.

• (c)

  Structural integrity risks associated with damaged piles or inherent defects associated with the original construction or subsequent demolition and/or redevelopment. The integrity of existing piles was established by detailed examination of representative piles. These included both piles scheduled for incorporation into the works and some that were not required for reuse. The checks included direct inspection, sonic echo testing and parallel seismic testing.

• (d)

  The capacity of existing piles. Piles were selected from the existing piles not scheduled for reuse and were progressively loaded to failure to determine their ultimate capacities. The piles chosen for testing were founded in different ground conditions across the site to understand whether or how such variations might affect performance.

After visual inspection of each steel element, it was found that almost all of the 6000 members of the frame could be reused. Some were repaired or strengthened to enable reuse, but the majority were justified to support the new loads in their current condition.

This assessment of the steelwork was refined as the design was developed, including a careful assessment of the original loading and visual condition surveys of each member. A key part of this analysis for the original columns was that, by interrogating the original design code (1909 London County Council Building Code) and extracting key factors and criteria, a modified buckling curve could be plotted against the relevant Eurocode. This meant that only eight columns on the project had to be strengthened, resulting in a significant cost and programme saving from original estimates.

The roof trusses of Turbine Hall A are a key feature of the building, but they required strengthening to support new landscaping loads. The original concrete roof deck was replaced and every truss was analysed separately with a menu of strengthening requirements. These included (a) the replacement of original members with new members of the same size but thicker sections to provide more strength, (b) the replacement of original rivets with modern dome-headed bolts and over-plating of original gusset plates and (c) the replacement of edge members where corrosion was too severe. All the steelwork was grit blasted and repainted, and all of the works were done from a series of temporary mobile platforms that moved along the original gantry crane rail.

The new structure within BPS followed a box-in-box strategy, with the new frame having to restrain several of the original building elements while meeting modern standards. A box-in-box approach was adopted to prevent overloading the existing frame while maximising spatial efficiency and optimising the structural intervention.

The new structures in both the switch houses and the boiler house are steel framed with concrete floors. The new frame within the boiler house contains different usages stacked vertically – a car park and retail, office and residential spaces – all of which ideally require different column grids. Through engineering optimisation, the usages were achieved with only two efficient transfer levels, one of which doubles as a plantroom (Figure 11).

The project was extensive and there are numerous significant examples that demonstrate engineering complexity, excellence and innovation. The sections below highlight the flavour of the responses to meet the building design requirements and address the existing building constraints.

To maximise the residential area, an ambitious 11 m A-frame truss cantilever was developed over Control Room A, the heritage jewel in the crown. This required a carefully considered construction sequence and pre-setting strategy to ensure that all agreed-upon tolerances were met. This included a jack on each truss, installed from the outset, enabling individual adjustment of each of the trusses. The truss can be seen in Figures 4 and 12.

Two vast tree-shaped steel structures each support a 30 m × 30 m office floorplate over eight storeys while also serving as architectural focal points within the column-free atrium. Digital technology played a key role in designing and delivering these elements. The success of these spectacular forms, shown in Figures 13 and 14, was ensured by

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  The architect’s geometry generation

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  Buro Happold’s computational capacity for complex structural analysis

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  The steel contractor’s building information modelling capabilities for effectively reviewing fabrication strategies

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  The construction manager’s model federation and design management.

Of particular importance was optimisation of the geometry of the ‘tree’ branches to limit second-order effects and to ensure that out-of-plane loads could be directly transferred to the floorplates at levels 2 and 5, which ensured the branches remained as slender and elegant as possible. Similarly important was the connection between the steel branches and the concrete column. Exceptionally high loads required a high-strength grout to flow throughout the connection interface, and a one-to-one plexiglass replica of the connection was made and tested three times to ensure grout flow into all areas.

One of the reasons for the tree structures was to create a column-free space in the north atrium. In addition to the trees, this column-free space required several large steel elements. A single 62 t, 2.1 m deep beam spans 26 m between the two wash towers. Part of the logistics challenge was installing the bearing elements for this beam, which were 5 t L-shaped steel elements that sit within the historic wash tower brick and are supported by the new 300 mm thick liner wall.

The creation of the south atrium showcases the grandeur of BPS, creating a sense of space and allowing light to enter the office and retail spaces. The narrow nature of the space called for a light and transparent solution. A bowstring truss solution was developed (Figure 15) and a key element of its success was the installation sequence and the transfer of load from the external historic temporary work trusses to the delicate new trusses. The lightness of the structure meant that turnbuckles were limited, and the whole system was adjustable at only one location per vertical truss. This required an elaborate pre-setting strategy with a highly controlled sequence and hold points.

The original structure comprised two distinct power stations, constructed in three phases. Despite its apparent symmetry, several significant distinctions existed within the building. A principal alteration executed was the pursuit of symmetry in the boiler house footprint above level 5. This initiative prompted the relocation of the west wall approximately 6 m westward, generating an additional 5000 m² of floor space across the upper levels. Consequently, a substantial 6 m cantilever was established, supporting the reconstructed west wall and facilitating six levels of new office space. This extension protruded from the roof of Turbine Hall A, a key heritage zone within the edifice. The cantilever was created by extending the level 5 transfer level, enabling the seamless transfer of the column grid to the retail grid below.

In order to both minimise the cantilever's length and optimise retail space, the new columns were positioned immediately adjacent to the existing ones. The new columns support 25 MN of load and are located 50 mm away from the original column, an integral part of the art deco Turbine Hall A and a significant heritage element. There was insufficient capacity in the original foundations and hence new foundations needed to be provided, which clashed with the original foundations that had to be modified. The original foundation was a strut-and-tie pile cap supported on 14 piles founded in London Clay. The new column is supported on a steel ground beam (Figures 16 and 17), which cantilevers out over a compression pile, with the rear section of the see-saw tied down by a tension pile. The existing pile cap was analysed and the design of the cap justified with reduced loads, which could be notched out to accommodate the new ground beam.

The top of the original foundation was at the level of the new finished floor level and the depth of the nose of the cantilever was limited; the tolerances for installation were thus incredibly tight. The original foundations, new foundations and the steel ground beams all had individual constraints and were therefore initially predicted to behave differently. The design of the new steelwork was fine-tuned to eliminate these differences to obtain a consistent response across all the columns. However, this still resulted in differential settlement between the two columns and, as such, the sequencing had to be carefully planned. In addition, this interface is 3 m below the water table and the constraints were such that a bespoke waterproofing detail had to be developed. Localised drainage was installed to reduce the water pressure and two different products were installed before the new system was loaded with the new superstructure dead loads before the joint was finally sealed once dead load settlement had taken place.

In addition to the Power Station itself, the project team designed and built an extensive new basement area around the full perimeter immediately adjacent to BPS (Figure 18). These areas were up to 12 m deep and undermined the original structure in some locations. These areas were dealt with locally. However, the bigger challenge the team overcame was dealing with the movements caused by the removal of overburden pressure. Initial predictions of total movement were up to 75 mm horizontally and 50 mm vertically, caused by the movement of BPS towards the large excavations. Analysis indicated that overall stability of the structure would not be affected, and the biggest concern was the damage that these movements could cause to the brittle original structure and potential impact. A series of fail-safe elements were designed to be installed if the movement reached a critical point. The movements were carefully monitored through a series of measures including precise levelling, movement monitoring, strain gauges and a team of seven full-time resident engineers. The movements were fed back into the modelling so that the results could be recalibrated. The movements followed the predicted pattern but with reduced magnitude, aligning with expectations due to conservative assumptions made during the modelling. Localised repair was required in a number of areas, but the fail-safe measures did not need to be activated.

The structures within the basement were generally designed as lightweight cellular steel frames with composite decking between perimeter piled retaining walls. The lowest of the basement slabs were designed to prop the Power Station, transferring high diaphragm forces to both their own stability systems and the structures of surrounding phases of the development, with the intermediate and podium slabs structurally separated to avoid load transfer to the new structure as a result of propping the existing. At the lowest of the basement levels uplift forces were found to be significant, as well as the high diaphragm forces the design needed to consider, heave pressures of up to 175 kPa and hydrostatic uplift pressures of 83 kPa. These were resolved through a combination of cellular heaveboard, below-ground drainage systems and the design of the basement slab. These necessitated robust waterproofing details at interfaces.

One of the most significant basement structures is the North Energy Centre (NEC), a below-ground energy centre situated to the north between BPS and the River Thames (Figure 19). The NEC includes a high-efficiency combined heat and power system that provides district heating and cooling to both the entire development and wider Wandsworth. It uses borehole extraction, which captures groundwater to be treated in water treatment tanks and used in the system, minimising demand on the national water network. The NEC was located below ground to reduce noise emissions and the excavation of 150 000 m³ of earth involved the use of river barges, saving 3500 lorry journeys on local roads.

The design of the NEC involved a number of complex interfaces, including five historic tunnels – two UK Power Networks (UKPN) tunnels cross the Thames connecting BPS and three historic tunnels connect BPS to the jetty and provide water inlet and outlet. The building superstructure was carefully coordinated to avoid directly impacting the tunnels, with the foundations designed to bridge over the tunnels where this was not possible. Monitoring was implemented in the UKPN tunnels.

At the interface with BPS, to maintain the movement joint between the historic steelwork and the new steelwork within the NEC, bespoke bearing details were developed. This involved removing rivets from the historic columns and fixing new fabricated bearing angles through the original rivet holes using new bolts through the existing holes (Figure 20).

The design of the NEC podium had a number of complex loading requirements which included:

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  responding to the client’s event strategy for North Park, which developed through the design of the structure

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  providing propping to the secant piled wall adjacent to the historic river wall structure to the Thames

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  supporting the ‘Halo Road’, which could be subject to all road-going vehicles

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  supporting a plant replacement strategy, which required a 1350 t mobile crane.

Zones for heavier event loading were established early in the design with the client, and clear zones were established for the plant replacement strategy. In addition, heavier elements of landscaping, such as deeper tree pits, were coordinated above column locations. This loading necessitated the use of bespoke fabricated steelwork and trusses below the podium and a high degree of coordination with the mechanical, electrical and plumbing engineering consultant and contractors.

Malaysia Square (Figures 21 and 22) is the feature entrance to BPS, designed as a series of stone steps that form a sunken amphitheatre to accommodate events located to the south of BPS at the interface of Electric Boulevard (phase 3) with the BPS building. The steps are crossed by three interconnected footbridges as well as a road bridge, which was installed at a very early stage of the project to be used for construction logistics. This required full integration with the overall site logistics, as well as having to deal with a variety of temporary cases as the ground was excavated below the bridge up to 20 m deep and then built back with the new superstructure, which provided the permanent lateral support to the bridge columns.

Three storeys of basement below the steps accommodate retail, back of house storage and a loading bay for BPS. The steps required complex modelling to analyse the vibration response of the concrete steps on the lightweight composite decked slab. The final design required a high degree of coordination between the concrete bowl and the steel frame required for the cladding as the structure transitioned from horizontal to vertical, as well as at the interface with the Halo Road Bridge, the pedestrian bridge above and the interface with the phase 3 structure.

Each of these structures have their own movement requirements, and elastomeric joints were carefully disguised within the strata of the steps that connect to movement joints in the slabs and the bridges to eliminate warping stresses within the structure.

Malaysia Square forms the focal point at the south face of BPS and is the primary entranceway from the wider Battersea and Nine Elms redevelopment and the new Northern Line underground station to the south. Integral to this public space are two new bridges, one road bridge and one pedestrian bridge, which delineate the oval-shaped square. The bridges are an essential part of how visitors will experience their arrival at BPS.

The road bridge forms part of Circus Road, which encircles BPS and played a key strategic role throughout the project. It was constructed as part of an early works package in order to provide vital construction access to the development.

The bridge is formed by a steel–concrete composite ladder deck arrangement with tapering cantilever cross-members, with all steelwork fabricated from plate (Figure 23). The curved superstructure is continuous over five spans, with a total length of 95 m and width of 10 m. The superstructure is supported by integral twin-column piers. The steel columns, approximately 18 m long, were constructed by plunging into single large-diameter concrete piles, so that construction of the bridge could take place ahead of the excavation of future basement levels directly beneath the bridge. With no structural bearings, articulation of the bridge is achieved by the flexibility offered by the unbraced columns.

The bridge is positioned at the boundaries of three project phases, each with a different contractor and architect. Three of the deck spans are incorporated into surrounding podium structures, which extend down to three basement levels below the bridge, leaving only two of the central spans visible in the final condition. The many complex design interfaces required careful management over several years to safeguard the structural integrity of the bridge. Movement joints at all interfaces ensure that the bridge remains an independent structure and structural monitoring was employed to provide real-time movements during the excavation works.

Finally the bridge was furnished with new surfacing, soffit cladding, laminated glass parapets and bespoke bollards with integrated lighting to provide vehicle restraint on the speed-restricted road (Figure 24).

The footbridge that spans over Malaysia Square (Figures 25 and 26) provides access to the BPS building at the upper ground floor level and consists of three spans connected in an arrangement resembling the Greek letter pi. The principal east–west span has an overall length of 28 m and is intersected by the two north–south spans, each 13 m long. The width of the deck varies from a minimum clear width of 3.7 m. The bridge has lighting integrated into the handrails of the laminated glass parapets and rigging anchor points are provided for the hosting of special events.

The superstructure comprises a trapezoidal box girder, fabricated from welded steel plate, spanning between new podium structures and the BPS building. The bridge has no independent foundations. This, together with constraints such as cranage limitations, imposed strict restrictions on the bridge self-weight and construction sequence.

The bridge was prefabricated and delivered to site in five sections. In order to achieve a slender profile in elevation and reduce the steel tonnage, the bridge was designed to maximise material efficiency, with provisions made for the future installation of a pair of tuned mass dampers to control pedestrian-induced vibrations. Prior to opening of the bridge, the design team partnered with Leeds University to undertake detailed dynamic testing to measure the real response of the bridge to simulated pedestrian loading. The results demonstrated that tuned mass dampers were not required due to the enhanced damping effect of the deck finishes, which were not accounted for in the codified dynamic analysis. This approach to the dynamic design therefore ultimately improved constructability, delivered cost savings to the client and significantly reduced the embodied carbon dioxide of the structure through material savings.

The Coaling Jetty (Figure 27) is a Grade II* listed reinforced concrete jetty located on the River Thames in front of BPS. It was constructed between 1929 and 1932, inside temporary cofferdams, with two cranes that serviced BPS in the loading and unloading of coal from barges until it was decommissioned in 1983. The design and construction of the Coaling Jetty was well documented by Bartlett and Cadwell (1935), which provided a useful source of information in evaluating proposals for its reuse.

The jetty was reused during construction of phase 1 and for the London Underground extension up until 2014 to remove soil from the site, after which the cranes were removed. The client wanted to use the jetty for events in a temporary use prior to reinstatement of the cranes. To enable reuse of the jetty, two temporary bridges were instated between the historic river wall and the jetty, with additional servicing provided from the main energy centre. The condition of the jetty was generally good considering it was heavily used in an aggressive external environment for nearly 100 years. However some cracking was observed to the underside as a result of movement joints seizing up over time (Figure 28). Monitoring points were established on the cracks with a regular inspection regime to establish any future movement and the structure established as safe to reuse. The Coaling Jetty is now open to the public and provides a vibrant extension to the public realm within North Park.

Reuse of the structure was an integral part of the engineering and architectural vision for this project, and the varying conditions of the fabric throughout the building and external areas have been described in this article. When historic fabric is retained and the design life extended, it is vital that ongoing inspection and maintenance strategies are implemented. At BPS, Buro Happold are committed to ongoing inspections to review the building structure and catalogue any structural defects or areas of degrading fabric. This informs the ongoing client maintenance strategy for the building and is necessary to ensure that the historic fabric remains in a serviceable condition and fit for its intended use.

The project is of international significance and had a huge amount of exposure both within the industry and capturing the public imagination. The construction works have appeared across national and international media, including TV documentaries and the BBC’s The One Show. The public can see the old building and how it interfaces with the new, creating an educational and cultural venue and showcasing what is possible to the wider world.

During construction, the redevelopment of BPS created over 200 local construction apprenticeships. Over 400 jobs have been created through Battersea Academy for Skills and Employment, a recruitment service connecting employers with job seekers from the Boroughs of Wandsworth and Lambeth. Post-completion, over 6600 jobs have been created (to date). Once the masterplan is complete, this number will rise to over 20 000.

The project would not have been possible without the close collaboration of the entirety of the design and construction teams. The structural engineering team of up to 50 people was site based for 5 years, and close relationships between the teams allowed the project to happen. The project was a huge learning experience for everyone involved and the team are taking these skills and experiences and lessons learnt back to the rest of the industry: currently this is occurring through delivering external lectures and continuing professional development courses.

The project has inspired those who have been involved and created magnificent spaces. Every opportunity has been taken to share learning experiences across the industry and showcase to the public what structural engineering can do to unlock transformational regeneration projects with the juxtaposition of old and new.

This paper has provided an indication of the engineering complexity and achievement to bring the iconic BPS back to life, while maximising preservation of the existing fabric and solving highly complex problems in an elegant and simple way. Restoration of the iconic BPS (Figure 29) and London Underground’s Northern Line extension were the main catalysts for the Nine Elms regeneration. Acting as chief placemaker, the regeneration of BPS led the way for social, economic and environmental transformations to the whole area. The regeneration project has undoubtedly been a huge success, creating a new town centre for Wandsworth with over 150 shops, bars, restaurants and leisure venues now open. More than 23 million people have visited the riverside neighbourhood since the Power Station and Electric Boulevard opened in October 2022.

Thousands of individuals were crucial to the success of this project and it is not possible to try and name them all, nor all of the organisations they have worked for. The authors would, however, like to give special thanks to the client (Battersea Power Station Development Company) and extend their own personal thanks to the following people from the Buro Happold Structural Engineering Team who have made this such a special project to work on: Justin Phillips, Wolf Mangelsdorf, Hayden Nuttall, Rob Edwards, Gregoire Martin, Azat Tatygulov, Matthew Duckett, Adrian Griffith Smith, Hugues Vernet, Selina Tan, Jim Solomon, Peter Page, Tim Kelly, Julian McFarland, Keith Wilson, Nick Hodgkinson, Gemma Turner, Simon Wheeler, Les Johnson, Claudia Leon Pena, Edmund Metters and Thomas Eckhart.

In addition, the authors acknowledge Wilkinson Eyre (architect), Mace (construction manager), Turner and Townsend (project manager), Gardiner and Theobald (cost consultant), LDA (landscape architect), Purcell (conservation architect), DP9 (planning consultant), RKD (temporary works designer), as well as several of the main contractors on the site who helped to make construction possible (Mitchellson, William Hare Ltd, MPB, Hollandia, Careys, Coffey Group, PAYE, Bauer and Keltbray).