History
The Queen’s Tower is all that remains of the Imperial Institute, which was built to mark Queen Victoria’s Golden Jubilee in 1887. The tower is 16.50m x 16.50m on plan and 87.00m high, clad in Portland stone and topped by a copper covered dome. There is a projecting stone balcony at first floor level and various decorative stone features around the base of the copper dome.
The Imperial Institute was constructed over a six-year period and was opened in 1893. The institute was not a great success and in 1899, the University of London took over half of the building as administrative offices.
In 1953 the government announced the scheme for the expansion of Imperial College and by 1956 it was public knowledge that this would involve the demolition on the Imperial Institute, following considerable opposition it was decided to retain the central tower.
Partial demolition began in 1957 and this continued until 1967. Between 1966 and 1968, work was carried out to enable the central tower to stand on its own. This involved creating massive foundations and then substantially rebuilding the lower portion of the tower.
Initial Enquiry
JDC Scaffolding were approached in 3Q 2020 to provide an outline design scheme and budget costings to provide scaffolding to the complete tower to give access for repairs to the external stonework and replacement of the copper coverings to the domed roof. The design was to include for a 2 Tonne Passenger/Goods Hoist and a full height Haki Staircase. The external scaffold was to be designed with minimal ties into the structure. We were asked to consider leg loads due to tunnels and voids below the scaffold area. Due to the specific access required to the copper dome we developed a proposal for beamed support over the complete area of the tower with a suspended access scaffold following the profile of the dome.
We engaged with our consulting engineers, RDG Engineering, to discuss and develop the outline design and to calculate expected leg loads and reactions. All was based on the very limited drawn information of the tower available at the time.
Costs and initial design information was submitted, and we awaited further instruction.
Design Development
We were contacted again in 2Q 2021 and were asked to contact Imperial Colleges estates engineer, to discuss the scheme further. Due to the Covid restrictions at the time we communicated via a series of collaborative Teams meetings, together with RDG, to discuss the further scheme requirements.
We were told at this time that due to the assumed fragility of the tower that we would be unable to physically tie to the structure so RDG were tasked with producing a freestanding structure to surround the tower.
A design was developed which incorporated an external “Exoskeleton” which comprises of a ten identical scaffold towers, built as a continuous scaffold, surrounding the tower. This structure is built to support the reactions of the other elements – independent scaffold to the face of the tower, hoist and Haki staircase.
The exoskeleton was designed as a double width scaffold with triple, double and finally single standards to differing heights, with a very specific bracing pattern. RDG were also asked to produce a Proof of Concept report, which included leg loads, for analysis.
We were asked to update our budget costing to make allowances for the changes at this point.
Scheme Development
We were contacted again in July 2021 to look at developing the conceptual design to include costing for various items required by the following trades. Items considered were:
Backpropping
Provisional allowances included in the voids below the tower to transfer imposed scaffold loads.
Loading Platforms
Erected at high level for distribution of the required roofing materials
Copper Dome Access
Access scaffold developed to ensure access to the decorative cupola at the top of the copper dome and the projecting finial above.
Temporary Roof
It was decided to include temporary roof coverage over the structure to protect the dome whilst the copper coverings were removed and replaced.
Further to an exchange of information we were asked to step away from the project as it would be going out to competitive tender, and we would not be able to quote for the works should we still be actively involved with the project.
Scaffold Tender
In May 2022 the project was sent out for a competitive tender process with a limited number of tenderers.
The tender pack included a full RDG Engineering design which had been further developed, since our last involvement. The main change was that the exoskeleton was now designed as double width scaffold to the full height. The design also now included a bespoke circular temporary roof, details of the required backpropping in the vaults and a full height hoist run off with staggered exits at 4.00m centres at each side of the hoist.
We updated our costs accordingly to ensure a compliant bid based on the specific requirements of the tender enquiry especially with respect to Health and Safety, deliveries etc. We also developed the build sequence and staged hoist installation methodology. We were also asked to provide costings for a full decorative banner to the complete external scaffold and other ancillary items.
During the tender process we provided quotations to all of the tendering contractors.
Contract Award
We were advised in August 2022 that Russell Cawberry had been successful in securing the Queens Tower contract. We had sent our quotation to Russell Cawberry, but had not worked with them in the past. We were not, therefore, confident in securing the project especially due to the size of the subcontract.
We met with the management of Russell Cawberry and they provided us with a further updated design scheme. The new scheme omitted the additional width of scaffolding to the exoskeleton, removed the external banner and included a revised bracing scheme to connect the exoskeleton to the inner access scaffold.
After a further round of price negotiations, some due diligence and, based on our long-standing knowledge of the project, we were finally awarded the contract by Russell Cawberry in September 2022.
We had a series of meetings with Russell Cawberry and the client to ensure that we understood the complexities of the scheme and were fully aware of our responsibilities of working at close proximity to a live college campus. The tower is situated within a quadrangle of the college and is surrounded by buildings, with, as well as the college students, both the Project Manager and colleges own Health and Safety staff having a very clear view of our operations.
Scaffold Brief
Design – General
The works are extremely design intensive and the design itself is based on a very specific set of guidelines which has been developed by RDG Engineering, as set out above.
Main Scaffolding
An 83.00m high freestanding scaffolding to an historic stone tower to give access for repairs to the external stonework and replacement of the copper coverings to the domed roof.
An external “Exoskeleton” which comprises of a ten identical scaffold towers, built as a continuous scaffold, surrounding the tower. This structure is built to support the reactions of the other elements – independent scaffold to the face of the tower, 2 Tonne Passenger/Goods hoist and Haki staircase.
The exoskeleton has triple standards to the 30.00m level, double standards to the 50.00m level and single standards to the 83.00m level. Every pair of standards are ledger braced, each horizontal bay plan braced and every vertical bay sway braced to both the internal and external faces.
Inner and outer scaffolds are tied together and braced in all directions.
Fully boarded independent scaffold to the faces of the tower with inner guardrails and boards joined with Safelinks.
Hoist Run Off
Full height hoist run off with 2 Tonne capacity beamed run off platforms. Hoist platforms staggered at either side to allow head room and access to every working lift.
Backpropping
Included in the voids below the tower to transfer imposed scaffold loads. Scaffold locations digitally set out in vaults to ensure correct transfer of loads.
Copper Dome Access
Suspended birdcage scaffold to give access to the full roof, decorative cupola at the top of the dome and the projecting finial above.
Temporary Roof
Haki temporary roof over the whole structure to protect the dome whilst the copper coverings are removed and replaced.
Skills and Expertise
The project highlights our design capabilities and the depth of our engineering knowledge and strong working relationship with RDG Engineering, the early design development was carried out in during the Pandemic via Teams and frequent telephone calls and email exchanges.
We have suggested practical, workable and cost-effective solutions to all areas of the works. Our workforce has adapted well to strict working practices and processes and the build on site is well constructed and aesthetically pleasing.
We have erected an extremely complex scaffold on this project and have met Russell Cawberrys programme requirements.
JDC Scaffolding have a pedigree of delivering very large and very complex tube and fitting scaffolding projects. The Queens Tower, although having an extremely complex design, the actual build is very repetitive on a pattern around the tower. Each bay of the external exoskeleton has a very specific bracing pattern – ledger, plan and inner and outer sway which has to carefully repeated, our quality control has, therefore, has had to be extremely diligent.
We have ensured that our site team, supervision and visiting management have been constant to ensure continuity throughout the life of the project build.
Our Senior Management Team have been regularly on site to review progress, provide advice, explore options and implement solutions to site issues.
We have had the agility to respond to challenges soon after their discovery which has been vital for Russell Cawberry in maintaining progress and achieving their programme.
We have worked closely with the Russell Cawberry team and have built trust and strong relationships which have enabled us to collaborate successfully on the project.
We pride ourselves at all times on our attention to detail with our final delivery on site. The completed scaffold on this project is testament to this.
Challenges
Challenge 1 – Stone Steps
Fully surrounding the tower and extending around the apron is a set of York Stone steps. The main scaffold and the exoskeleton had to be based out on this surface. Due to the exact setting out requirements, some of the standards would be located at the nosing of the existing stonework which caused a problem.
We developed a protective covering for the steps, which also took into account the huge leg loads, made up of two layers of plywood with a high-density insulation infill.
A system was developed utilising Steel UC’s and steel plates to extend the going of the stair treads to accept the standards and to transfer the loads.
Challenge 2 – Vaults
Under the tower are a series of vaults with a minimal amount of drawn information. Early in the project this area was deemed a Confined Space.
We trained our operatives appropriately and worked with RDG to develop a robust backpropping system from tube and fittings and RMD equipment.
We worked alongside a Confined Space supervisor and Top Man and erected the required propping, then worked alongside an external surveying company to ensure that the props were located in the correct positions so that loads were correctly transferred to the slab below.
Challenge 3 – Temporary Roof
The original designed roof was a client led innovative circular design, covered with Shrinkwrap. We developed this design, alongside RDG into a workable solution utilising Haki equipment (where possible), bespoke triangular roofing sheets and a fabricated inner support module.
The finished effect would have been aesthetically stunning, however, we highlighted that buildability would be an issue, and that we would require a complete boarded platform below the roof to give us safe working access. The bespoke sheets and central support module were also expensive and would have one use which we did not deem as sustainable. Also the central area would not be completely watertight which would defeat the overall need for a roof.
Water management was also highlighted as an issue as there would be ten separate short lengths of gutter, our new design has just two gutters at each side.
The build itself was completely bespoke with untried materials, we did not feel we could produce a SSOW especially at the extreme height we are working at.
We later worked with RDG to develop a more user-friendly square duo pitch Haki solution. This would use traditional materials and methods, which our operatives are fully trained. The cost and programme savings proved significant enough for a change in methodology.
Challenge 4 – Copper Dome Access
We have worked with RDG to develop a bespoke suspended access scaffold for the copper replacement works to enable access to all faces of the existing dome.
There is a complex beamed support detail at the top of the dome which doubles as a support for the suspended birdcage below and the temporary roof above.
The Coppersmiths working on the copper replacement have very exacting standards of distances of working platforms from the dome as well as the precise finish to the working platform.
The hoist run offs are to be extended across to the dome to allow the old materials to be removed and the new coverings to be stored until use.
Challenge 5 – Working within Imperial College
The site itself is within an internal quadrangle of Imperial College known as the Queens Lawn. The site is surrounded all sides by college buildings. The tower itself due to its location and height is very visible, from the surrounding areas and by students and staff.
Part of the contract terms were very specific about noise levels, especially with regards to Impact Wrenches. We have discussed our works at length, explained that scaffolding is inherently noisy with most operations. We have developed a good working relationship, are allowed to use our wrenches and respect designated quiet times, especially around examination times.
Imperial College is a very busy establishment with a large daily footfall past the tower. Taking this into account we have made sure that the external finish of the scaffold is neat with no projecting tubes. The structure is now being seen as an art piece and Imperial College are looking to introduce uplighters through the structure to highlight the complexity.
Imperial College are championing the project on their website and regularly upload timelapse footage of the build. The Queens Tower is the Jewel in the Crown of Imperial College, and they state, “This project will provide at least 50 years of further life to the external fabric of the highly visible icon of Imperial College London”. This refurbished building should give a collective benefit to the college and the wider community.
Challenge 6 – Material Logistics
The build is logistically challenging due to the sheer volume of materials required – approximately 300,000 ft of tube, 100,000 fittings and 6,000 scaffold boards together with the required ancillary items, beams, Haki Stair items etc.
There is a very strict booking in process with the college, so we have to ensure that each weeks material requirements are worked out in a timely manner to ensure correct items, cut tube lengths etc are available as and when required.
The physical site is very small and there is no real storage areas so the materials have been delivered as they would be to a tight city site and raised to the working level via the hoist ensuring speed and continuity of the build above.
We work closely with our hoist supplier to ensure each 10.00m raise of the mast is booked in to ensure as little programme downtime as possible.
Challenge 7 – Budget
The continually developing design has raised a number of savings. We have worked closely with the Russell Cawberry commercial team to ensure transparency and best value at all times.
We have also strived to ensure that any items of variance are priced, where possible, in a timely manner to enable works to be agreed early with the client team wherever possible.
Awards
JDC Scaffolding were shortlisted for the 2023 NASC Award for Project of the Year (Medium) and picked up the award.
