{"id":509103,"date":"2024-11-08T10:05:10","date_gmt":"2024-11-08T10:05:10","guid":{"rendered":"https:\/\/www.constructionnews.co.uk\/?p=509103"},"modified":"2025-02-05T10:58:02","modified_gmt":"2025-02-05T10:58:02","slug":"building-on-the-edge-maces-latest-london-bridge-project","status":"publish","type":"post","link":"https:\/\/www.constructionnews.co.uk\/sections\/long-reads\/building-on-the-edge-maces-latest-london-bridge-project-08-11-2024\/","title":{"rendered":"Building on the Edge: Mace’s latest London Bridge project"},"content":{"rendered":"

Mace is sticking to strict sustainability criteria on its latest project in London Bridge<\/strong><\/em><\/p>\n

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Client:<\/strong> Edge Technologies
\nProject value:<\/strong> \u00a3230m
\nArchitect:<\/strong> Pillbrow and Partners
\nSite size:<\/strong> 25,548 square metres
\nPiling:<\/strong> Cementation Skanska
\nConcrete frame and basement:<\/strong> Morrisroe
\nSteel and CLT:<\/strong> Severfield NI
\nFacade:<\/strong> Permasteelisa
\nTwin lifts:<\/strong> TKE
\nMEP:<\/strong> Shepherd Engineering Services
\nDemolition:<\/strong> Keltbray
\nConstruction start:<\/strong> May 2023
\nExpected handover:<\/strong> July 2026<\/p>\n<\/div>\n

Mace has its stamp all over a small patch of SE1, east of London Bridge and south of the River Thames. The firm\u2019s hoardings still line St Thomas Street more than a decade after the tier one contractor completed the Shard. The firm\u2019s other jobs in the area include the luxury apartments rounding off Shard Quarter and the 39-storey student accommodation tower opposite London Bridge Station.<\/p>\n

Eagle-eyed commuters might have noticed another Mace-branded concrete core shooting up in recent months next door to the student tower. Its hoardings look a bit different though. \u201cHi! I\u2019m Edge London Bridge, nice to meet you,\u201d they say. \u201cI am 275,000 sq ft of workspace shaped for tomorrow.\u201d<\/p>\n

On a sunny summer\u2019s day, Construction News <\/em>took a look at the early-stage concrete works. Architecture firm Pilbrow & Partners\u2019 designs for the 27-storey tower certainly have several hallmarks of the aspirational post-Covid workplace. They include a flexible exoskeleton
\nthat allows tenants to divide the space how they see fit, and an exposed cross-laminated timber feature staircase leads to a community auditorium. There\u2019s also landscaping that filters through from the street, blurring the boundaries between inside and outside.<\/p>\n

But the most important aspect \u2013 at least where client Edge Technologies is concerned \u2013 is the building\u2019s climate impact. The Dutch developer has set itself tough environmental standards for its first UK project, which it claims will be London\u2019s most sustainable office tower. \u201cEven before we got to the usual conversations about programme timetables and cost, the client was asking about the carbon impact of each decision we were making,\u201d says Mace project director Stuart McDonald. \u201cThere were some things it wouldn\u2019t negotiate on.\u201d<\/p>\n

One of those non-negotiables was a cap on embodied carbon, which was sealed into the construction contract. Mace was already on the same page. The contractor has its own strict carbon targets, including a pledge to help its clients save 10 million tonnes of carbon by 2026, the same year it plans to complete Edge London Bridge.<\/p>\n

The building is on track to meet an alphabet soup of environmental credentials. It is aiming for BREEAM Outstanding, NABERS 5*, a Paris Proof energy use target of 55 kWh\/m\u00b2, 100 per cent FSC certification for timber used on site, 98 per cent minimum diversion from landfill and a 35 per cent embodied carbon reduction in comparison with its RIBA stage three design. All the data needed to prove the building meets its targets is stored in Mace\u2019s proprietary sustainability software, Optimise, and presented to the client quarterly.<\/p>\n

Underground, overground<\/h3>\n

The 25,550 square metre site is conveniently located next to London Bridge Station \u2013 the country\u2019s fourth busiest \u2013 and a vibrant high street adjacent to the gastronomical paradise of Borough Market. Becket House, a seven-storey 1980s concrete block used as a government immigration reporting centre, was demolished before Morrisroe commenced the groundworks in October 2023.<\/p>\n

Subcontractor Cementation Skanska cored through 150 existing piles to put in 335 new ones. \u201cEven now, we\u2019re still digging out the piles from the old building, even though we\u2019ve been here for well over a year,\u201d says McDonald. Some of the existing piles went deeper than the four-level basement Mace is currently excavating, despite the old building being four times shorter than Edge\u2019s 108 metre height. Cementation used a combination of continuous flight auger method, rotary piling method and the deeper bearing piles were installed using polymer as a support fluid. Mace also discovered pavement defects around the site perimeter, which it backfilled with Cemfree concrete, a mix free from carbon-intensive Portland cement.<\/p>\n

A top-down construction approach to the basement limited disruption from underground unknowns \u2013 necessary as the programme is already on the long side at 169 weeks, McDonald says. It took six pours for basement subcontractor Morrisroe to cast the ground floor slab before it began to excavate the 16.6 metre-deep basement. The four basement floors are supported by 40 plunge columns, the biggest of which is 21 metres long and weighs 27 tonnes, allowing Morrisroe to cave below. The ground floor slab capping the basement also supports a jumpform core that is rising up at the east of the site, while a steel mega-truss goes up alongside.<\/p>\n

Concrete jungle<\/h3>\n

Mace tackled the concrete carbon-reduction challenge in a number of ways, working with concrete frame subcontractor Morrisroe to develop bespoke mixes and rationalising the design of concrete elements so less was needed overall. When CN<\/em> visits, Mace is still excavating the basement and has only cast eight of the 27 storeys. Yet the team has already reduced carbon by 21 per cent compared with RIBA stage three designs \u2013 cruising towards its 35 per cent target.<\/p>\n

This blended approach to reducing concrete\u2019s carbon impact is best demonstrated within the building\u2019s piles. The concrete mix replaces 70 per cent of carbon-intensive Portland cement with ground granulated blast furnace slag (GGBS), a byproduct of steelmaking. GGBS mixes perform like regular concrete but take much longer to harden to full strength. \u201cYou can have high GGBS in piles because you\u2019re not after rapid strengthening,\u201d says Mace engineering lead Tom Webster. \u201cYou pour them and then you can wait almost a year before you\u2019re going to put anywhere near the amount of designed stress on them.\u201d<\/p>\n

The piles have been designed to be smaller, cutting down not only on concrete, but also on rebar and polycarbonate. Fibreoptic cables sit within some of the piles, loosely tied to the rebar, going down all the way from the ground floor to the bottom of the pile about 55 metres below. The pile monitoring system should stay in the building for 10 years, to help assess loads over time. Mace hopes the data collected will help it rationalise pile design on future projects, and work out what temporary works are needed to support the next stage of the current build. \u201cWe want the building to work really hard for us as we\u2019re constructing it as well,\u201d says McDonald.<\/p>\n

The ground floor slab is more cementitious, at 40 per cent GGBS. \u201cWhen you pour slabs, hardening time is critical, because you want to be able to load them again as soon as possible so you can build on top,\u201d says Webster.<\/p>\n

A 40 per cent GGBS concrete is also being used in the jumpform core, a method chosen over slipform in part because it allows longer for the concrete to harden before it takes weight. Post-tensioned slabs will make up about 80 per cent of the floorplate of the upper levels, further minimising materials. Each upper floor plate will be 1,080 metres square: 805 of post-tensioned concrete, 107 of reinforced concrete and 168 of cross-laminated timber and steelwork.<\/p>\n

Material world<\/h3>\n

Although concrete inevitably makes up a big proportion of a project\u2019s environmental footprint, Mace has gone further in its quest for carbon savings. One success story was the rebar. Mace had already decided on a rebar supplier when Morrisroe came forward with an alternative that uses half the embodied carbon. \u201cIt had a huge impact,\u201d says Webster. \u201cWe\u2019ve got roughly three and a half thousand tonnes of rebar on the project. That\u2019s a big figure.\u201d<\/p>\n

Material reuse is also playing a significant role, not only because the project is targeting a minimum diversion from landfill of 98 per cent. Mace worked with structural steel firm Severfield NI to procure reusable temporary steelwork, which will either be taken to other projects or remain in place, encased in concrete or exposed.<\/p>\n

During the basement excavation, a skip descends from a gantry supported by plunge columns and the capping beam. Once the London clay is dug out, the gantry system transports it upwards onto the back of a lorry, which will take it away to be remodelled into signs and nameplates installed outside and in the reception area.<\/p>\n

It\u2019s an example of the attention to detail that makes Edge London Bridge a worthy neighbour of the Shard and its other Mace-branded bedfellows. \u201cWe look across at all these feature projects north of the river,\u201d says McDonald. \u201cIt won\u2019t be long until north of the river is looking at all the feature projects south of the river.\u201d\u00a0\u00a0<\/strong><\/p>\n

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Lasers set to stun<\/h3>\n

A quirk of Pilbrow & Partners\u2019 internal design is that the concrete doorways to the lifts will be exposed. There will be a lot of these exposed doorways, acting as the threshold to Edge\u2019s 27 storeys and four basement levels.<\/p>\n

Typically, when calculating where to make an opening in a core, a subcontractor measures from one corner of the shaft. This method is moderately accurate, but the client and architect on EDGE wanted more precision. The solution lies in a set of bright yellow boxes at the bottom of the lift shaft, mounted on a grillage. Once each level of the concrete core is slip-formed, lasers will shoot out of those boxes right in the middle of the proposed doorway. This provides a consistent point from where concrete frame subcontractor Morrisroe can measure where to make the opening. Each door can then be set within 10mm of its vertical neighbour.<\/p>\n

The doorways will open onto a twin lift, which has two cars in one shaft. Edge is the only site in the UK currently installing a TKE twin lift, according to McDonald. The last building to feature them was Skanska\u2019s 52 Lime Street \u2013 otherwise known as the Scalpel \u2013 which completed in 2018.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Mace is sticking to strict sustainability criteria on its latest project in London Bridge Client: Edge Technologies Project value: \u00a3230m Architect: Pillbrow and Partners Site size: 25,548 square metres Piling: Cementation Skanska Concrete frame and basement: Morrisroe Steel and CLT: Severfield NI Facade: Permasteelisa Twin lifts: TKE MEP: Shepherd Engineering Services Demolition: Keltbray Construction start: …<\/p>\n","protected":false},"author":141524,"featured_media":509115,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ep_exclude_from_search":false},"categories":[82221,564,79553,559,557],"tags":[],"yoast_head":"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\t\n\t\n\t\n