Working at height: a subtle scaffold for the British Museum

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With a lawsuit similar nary other, the stipulations enactment connected WellMax Scaffolding’s squad to get the occupation close and support the priceless features astatine the British Museum harmless were tough. Tim Clark reports connected however the squad roseate to the challenge

Project British Museum refurbishment
Client The British Museum
Main contractor Curo Construction
Scaffolding subcontractor WellMax Scaffolding
Contract value (scaffolding subcontract) £500,000
Start date April 2020
Completion April 2021

They get successful the dormant of winter. Their ngo is to assemble a pinpoint-accurate scaffold, hidden down a world-famous facade, to alteration the harmless replacement of an ageing extortion connected 1 of the world’s astir celebrated museums.

WellMax Scaffolding estimating manager Chris Maxwell-Smith says the unnamed unit enactment similar ninjas. So skilled are they astatine their commercialized and truthful sought aft are their skills that helium vows to support their identities a secret. “If I archer you who they are oregon springiness their names they’ll get poached by a rival,” helium jokes, arsenic helium reflects connected however his steadfast took connected the occupation of erecting a safe, unchangeable level for moving astatine tallness connected the Grade-I listed British Museum’s southbound colonnade.

Urgent repairs

Completed successful 1847, the neo-classical colonnade is 1 of the astir salient Victorian-era edifices successful Europe. The celebrated fluted columns of the museum’s expansive portico enactment a copper roof, which shelters the main entrance, but by 2020 the extortion was successful urgent request of repair oregon replacement.

Main contractor Curo Construction was tasked with replacing the aged copper panels and undertaking structural reinforcement enactment to fortify the extortion and forestall h2o ingress. The enactment included painstaking restoration of lime-plaster soffits, featuring 42 oblong coffers, which signifier the ceiling of the portico on the colonnade. This delicate enactment was tackled utilizing accepted plastering techniques.

“We had the structural constituent of wherever we could spot scaffolding and the ocular brief, truthful [visible] scaffolding had to beryllium minimised”

Chris Maxwell-Smith, WellMax Scaffolding

Gaining entree to the precocious levels of the immense depository was an engineering feat successful itself. Specialist scaffolder WellMax was contracted to plan and assemble a harmless moving abstraction for the main contractor, which would not “affect oregon disturb the building”, portion appearing arsenic discreet arsenic possible.

The thorough little from the British Museum provided a roster of constraints, including structural and aesthetic requirements, dealing with the nationalist and – fixed the timing of the job, which started conscionable implicit a week aft the archetypal lockdown successful England – COVID-safe moving practices.

Among those constraints was the request to guarantee the scaffolding made minimal interaction with the cloth of the historical building, and that the scaffold poles should not walk successful beforehand of the 13.7-metre-high Portland-stone columns, to support the museum’s iconic facade during the works. The operation had to beryllium designed to withstand upwind loading without putting immoderate strain connected the depository itself.

Maxwell-Smith says: “Even now, what strikes maine is the existent standard of the building. You don’t grasp conscionable however large the British Museum is until you locomotion close up to it. The columns are 1.5 metres wide, and the measurement of chromatic utilized successful the gathering and the ground-bearing value has meant that nary other load tin truly beryllium applied – oregon lone precise carefully.”

Bearing the weight

The British Museum was built earlier galore gathering regulations, specified arsenic those overseeing crushed loads oregon value distribution, were codified. The archetypal contented to flooded progressive uncovering a mode to assemble the scaffolding down the columns without placing excessive load connected either the gathering oregon the crushed instantly astir it.

Maxwell-Smith says: “Most buildings aren’t designed to person impermanent structures placed connected them, truthful they aren’t [necessarily able] to carnivore the other weight.

“The depository gathering pre-dates general-access loading conventions, truthful you had 2 facets to the build: we had the structural constituent of wherever we could spot scaffolding and the ocular brief, truthful [visible] scaffolding had to beryllium minimised. The depository didn’t privation to spot immoderate uprights successful beforehand of the gathering – everything had to beryllium hidden down the columns.”

The scaffold’s hefty extortion was designed to determination with the upwind – cleverly cutting highest load

Structural engineers moving for The British Museum stipulated wherever each of the scaffold bases could beryllium placed, close to the nearest millimetre, with constricted areas of 450mm by 2,000mm down each column. One cardinal determination was that the scaffold bases could lone beryllium placed wherever it was known that masonry walls and piers existed underneath. The scaffolding plan besides ran antagonistic to the accustomed norms by taking up arsenic small abstraction arsenic possible, successful opposition with the emblematic signifier of spreading load arsenic wide arsenic imaginable astatine crushed level.

The reply was deceptively simple, Maxwell-Smith recalls: “We said, ‘why don’t we usage modular beams?’” – which are 450mm wide. “We decided to basal those up and minimise the enactment [to instal the scaffold structure] for the guys moving astatine height. The modular beams besides came with pre-built bracing. That was the archetypal hurdle to overcome.”

Pre-constructed and wide available, scaffold beams signifier a halfway portion of a toolkit for ample projects, wherever they are typically installed horizontally. Using the 450mm beams arsenic a brace of uprights allowed the squad to absorption the scaffold loadings connected the peculiar areas successful a azygous manner, portion besides reducing equipment, labour clip and risk. The aforesaid alloy beams were utilized to signifier bridging sections betwixt the enactment towers.

Scaffold props were allowed to carnivore connected non-decorative level surfaces of the facade. No restraints were permitted connected the chromatic columns, however, and nary fixings could beryllium attached to the gathering fabric. Where the scaffold met the columns, guttering was utilized to signifier a protective lawsuit implicit the file itself.

The scaffold besides included a cantilever section, jutting retired astatine the apical of the operation to supply entree to the pediment – the triangular conception of the facade straight supra the columns – wherever further restoration was required. Knee bracing was installed to transportation the cantilevered loads backmost to the structural wall.

British Museum Colonnade Soffit Access Scaffold

The moving platform, with knee bracing and alloy beams

Priceless columns

The triangular pediment features a recessed space called a tympanum, which is elaborately decorated with an array of carved chromatic figures. Created by celebrated sculptor Sir Richard Westmacott, the artwork ranks alongside galore of the artefacts wrong the gathering successful presumption of humanities significance.

“The statues wrong the portico itself are priceless items,” Maxwell-Smith says. “It’s absorbing arsenic the British Museum doesn’t person an security policy. You can’t regenerate the statues arsenic they are virtually irreplaceable.” He adds that his squad were, unsurprisingly, “very, precise careful” erstwhile constructing the scaffold elements successful the vicinity of the carvings.

“We chose not to restrain the extortion fully, and really let it to determination subtly up and down. That meant that the loads we enactment into the gathering were overmuch smaller”

Chris Maxwell-Smith, WellMax Scaffolding

The biggest challenge, however, was not the creation but the elements. The scaffold and its ample impermanent extortion had to counteract upwind loading safely, and bash truthful without placing immoderate important further load connected the depository building.

Maxwell-Smith says: “To restrain a extortion of that size [over the museum] would instrumentality an immense value [of ballast] and we simply didn’t person that capableness successful the building. It was thing the depository simply wouldn’t let america to do.”

The squad came up with a astonishing solution to this conundrum. “We chose not to restrain the extortion fully, and really let it to determination subtly up and down,” Maxwell-Smith explains. “That meant that the loads we enactment into the gathering were overmuch smaller.” To power this movement, halt tubes were placed connected the scaffold. With a minimum spacing of 79mm betwixt the apical chord of the beam and the halt tube, the extortion could emergence successful the upwind by 65-85mm, which meant the value of the extortion itself would assistance to counteract the applied upwind load.

Novel design

This caller plan reduced the request for kentledge factual blocks to stabilise the structure, which would person added to the wide value placed connected the building. Where static loading was needed to minimise upwind movement, h2o butts were often hung from the scaffold successful penchant to factual blocks.

Maxwell-Smith recalls: “It was rather scary astatine times and [the structure] moved rather a lot, but we had assurance successful our designers and we did structural modelling. We went successful determination arsenic a team, with elder management, and wellness and information and declaration managers, to guarantee it was some designed and installed correctly.”

The “mesmerising” caller copper roof

With the analyzable task mapped out, it took six weeks to spot the scaffolding for the soffits connected the eastbound and westbound wings of the museum, with the wide task taking 18 weeks.

Once each of the scaffolding had been painstakingly enactment successful place, the operation supra the columns was wrapped, not conscionable to disguise the operation enactment but to conscionable the client’s tendency to support the look of the gathering arsenic acold arsenic possible. WellMax sourced and installed a mesh printed with high-resolution integer images of the celebrated portico and its sculpture, designed to replicate what was covered up arsenic intimately arsenic possible.

One twelvemonth aft the scaffolding went up, the restoration works were finished. “The completed works are perfectly fantastic to see,” Maxwell-Smith says. “The copper, which has replaced the ageing roof, is mesmerising. It’s a shame it tin lone beryllium seen with a helicopter.”

The palmy enactment to reconstruct this landmark gathering went connected to beryllium named Project of the Year by a Specialist Contractor astatine the 2021 CN Specialist Awards. Entries for the 2022 Specialist Awards are unfastened until 15 April.