Dubbed the ‘grandparent of the skyscraper,’ the iron-framed former flaxmill in Shrewsbury has been brought back to life as a workplace and museum by architects Feilden Clegg Bradley Studios. James Parker reports on how they worked with Historic England to rescue a major piece of the Industrial Revolution – with a light touch
Heritage restoration projects rarely have a more architecturally resonant backstory. Feilden Clegg Bradley Studios’ mammoth ‘creative reuse’ scheme brings Shrewsbury’s Grade 1 listed former flaxmill a vibrant new identity, as high-quality co-working spaces, plus a museum detailing its rich history. More importantly, working with client Historic England they ensured an enduring life for the building by repairing and supporting its pioneering but increasingly precarious 225-year old iron structure, harnessing its qualities for new uses.
It is another great example of architects celebrating existing structures and giving them a new context, and celebrating both. It’s also unusual, as an example of a national organisation working in partnership with a local community as joint custodians of a major architectural landmark.
The first phase of the refurbishment is the main building, which was converted into a maltings in the mid-20th century, and is known as the ‘grandparent of the skyscraper,’ despite only standing five storeys high, due to its cast iron frame. Flax milling carried a near-constant fire risk due to the combination of the steam-powered machinery, the airborne dust from the flax itself, and exposed flames, and the timber-framed buildings in which it took place were often destroyed by fire.
In 1796 a surveyor and wine merchant, Charles Bage, was commissioned to design a fireproof mill, having already been exploring the possibility of using cast iron for structural frames. He designed a grid of iron columns and beams, with 3 x 17 rows of columns on each floor, plus masonry jack arches completing the structural frame.
The beams holding the floors were built in two bolted-together sections. When the mill opened the following year, it was heralded as the world’s first iron-framed building, as well as the first purpose-built fire-proof structure, brick clad and creating the blueprint that would be adopted for much taller metal-framed buildings in coming decades.
The adjacent canal also opened in 1797, bringing in coal and taking away finished flax for the next 100 years, but the linen industry declined at the turn of the 20th century, and the mill fell into disuse. It was repurposed as a maltings, because the slim columns afforded the new owners the large floor areas needed to dry barley (its net internal area is 4181 m2). Malting required humidity, light and ventilation to be controlled, so most of the windows were bricked up.
The final addition was the Jubilee Tower, ironically built in timber and holding machinery to move barley from floor to floor. It was clad with an ornate iron coronet to celebrate Queen Victoria’s Golden Jubilee.
The building was also used as a barracks during the Second World War, and by the mid 1980s, it again fell into disuse, as modern malting processes took over. It was Grade 1 listed in the 1950s, having been regularly visited as a design landmark, but as project architect Tim Greensmith explains, it became “largely forgotten” as the century progressed – “it sat there with people not knowing what to do next.”
The case for development
FCBStudios were instrumental in advocating for and driving forward this complex restoration project, working with Historic England from the project’s inception in around 2010. “Report after report identified this site as key to any regeneration of the northern corridor of Shrewsbury,” explains Greensmith. “However, it was a difficult one to tackle locally, so the council had to reach out to Historic England, the Lottery Heritage Fund and others, to help them crack the problem of the last brownfield site in Shrewsbury.”
He says that Historic England “realised right from the start this was not an artefact, not a museum, and needed to be put back to work.” It needed to be a “catalyst for heritage-led regeneration,” as well as an exemplar of sustainable refurbishment, including renewable technologies. He adds however that Shrewsbury Flaxmill Maltings was a “one-off, so the solutions might not be applicable to all mill conversions.” Another unusual aspect was Historic England working as both client and advising the local statutory authority scrutinising the planned interventions, albeit “totally separately,” says Tim.
Being a 9000 m² building in an out of the way ‘sub-urban’ site, it was recognised from the outset that it would need to offer a mix of uses, to minimise its commercial risk, rather than being a speculative office scheme. The 2008 credit crunch was the end of hopes for a developer to grasp the nettle, but Historic England and their architects maintained the momentum, entreating the local authority to pursue the project.
However after local authority cuts, Historic England was the only organisation capable of taking it forward, and fortunately had a “great, and very experienced” project manager embedded in the project, says Greensmith, to help make it a viable proposition. “They understood historic buildings, but they also understood risk and how to manage it.” The contractor Croft Building Conservation (based in Cannock) was added as the third of a triumvirate that could deliver a cost-effective, pragmatic project that “wasn’t glorified preservation for the sake of it.”
The mix of uses soaked up design skills from various specialisms in FCBStudios’ architectural workforce, including conservation and other areas of client advice. They acted as strategic advisors to Historic England, writing the Conservation Management Plan, and developing the architectural vision for combining food and beverage, education and workplace elements. “We were able to bring in various people from our various sectors,” says Greensmith. He says the practice badges projects of this type as “creative reuse,” as “we love their history, but we are so focused on what they are going to be,” designing with an emphasis on future adaptability as well as sustainability.
Restoration approach
This painstaking and comprehensive £28m (fixed budget) restoration was driven by a ‘light touch’ approach to repair the fabric, doing what was required to retain and safeguard the structure and avoiding overengineering, with lean design and sustainability as the overall drivers. The practical goal was twofold; to repair metal elements of the structure which were in a sorry state after years of corrosion, and secondly, to bring the building up to modern thermal performance standards as a high-quality 20th century workplace, enhancing and harnessing its original features to that end.
FCBStudios has its own carbon calculation tool, which they used to demonstrate how a ‘light touch’ refurb would be the sustainable answer to the challenge. They used this to compare the embodied energy of the 600 tonnes of steel needed for a full facade retention scheme with the lighter ‘safety net’ approach, which would require 60 tonnes. They were also able to offset this with the improvements to the fabric, in the form of new high-performance metal windows, sheep wool insulation in the roofs, and wood fibre insulation for all compartmentalised spaces, allied to the major sustainability plus of a ground source heat pump installation.
The key structural drivers for the design of the refurbishment were to keep the ground floor open and free of columns where possible. This meant making most structural interventions on the first floor – which was the first of four levels devoted to tenanted workplace. There were fewer issues in terms of structural loadings on the upper workplace levels, thanks to the relatively lightweight planned office uses.
Designing a new future
Tim Greensmith says Historic England’s approach to such projects is holistic, looking at the whole building “and every possible aspect of energy conservation before jumping to renewables or triple glazing.” He explains that the architects applied Historic England’s national guidance here at Shrewsbury Flaxmill Maltings, and in turn FCBStudios “encouraged them to do research and innovation projects, looking at thermal enhancement of solid masonry, which is a really thorny issue in environmental upgrades.” The risk was over-insulating and thereby introducing other problems such as moisture into the fabric.
Historic England was nervous about potential outcomes of interventions, so with time not being a critical factor, and having a client with a rigorous technical team, FCBStudios suggested doing a trial run on product solutions for the refurbishment. This included sending materials for third party testing, setting up a weather monitoring station on site, and testing different insulation materials onsite, using probes mounted in the walls. These data were then analysed using FCBStudios’ modelling software, and the design and specification adjusted as needed, before presenting the findings to clients and other organisations such as academic bodies.
“We had a client that was interested in the real answers to these questions, not just getting what was required for Regs approval, and they were interested in learning lessons and disseminating them.” Historic England invested in a training programme for various strands of the industry, as well as apprentices in the heritage field, seeing this 10-year project as a crucial test bed for knowledge sharing on refurbishing major old buildings. The client for its part opened a visitor’s centre, and held open days when the public could visit and learn about some of the refurbishment skills being employed, such as lime mortar.
Rescue mission
Being the world’s oldest iron framed building – designed before building codes and full understanding of iron’s elasticity – most structural elements were understandably in a poor state. Cast iron performs well under compression but not under tension, and the weak points emerged over time, with significant cracks appearing where the columns meet the floors above, replicated across the whole frame. “The first engineer we spoke to said ‘you have to take it all down and rebuild it,’” Greensmith recalls, “but we said ‘nobody wants the world’s newest cast-iron framed building.’”
With the first floor being a generous floor-to-ceiling height, the architects were able to hide a lot of the structural strengthening members they introduced, in a steel grill raised floor, supported by six new steel columns placed along the central axis of the ground floor. A structural ‘failsafe’ was introduced in the form of steel stirrups which connect the grill to the ends of the original cast iron beams below; if one of the original columns or junctions between them and the beams fail, the stirrups will transfer the load to the wall and new columns.
A further measure was including a significant number of tie-rods which will (in the event of a cast iron element failing), take loads back through the masonry arches to the external walls. This bespoke solution was a result of the structural engineers AKT II taking a deep, investigative approach and “going back to first principles,” says Greensmith, not being driven by standard office loadings – instead they aimed for more moderate floor loads of 2.5 kN/m2, reflecting modern office requirements.
The restored facades saw the project triumph in several categories of the 2023 Brick Awards (including the Supreme Winner), but this aspect of the scheme was far from straightforward. Timber elements such as lintels, beams or pads under beam ends were all rotting to varying degrees, and had to be replaced with either concrete or grouting, and the leaves had to be tied back. In total, 112 new windows were added (in the apertures that had been bricked up in the conversion to a maltings). This results in one line semi-obscuring the building’s painted sign in an unusual way on the main facade. In total, 40,000 new handmade bricks from Northcot in Gloucestershire were used, and a large number were cleaned and reused, “but we had a real challenge on our hands to maintain the wobbles in the walls, to keep it looking a 225-year old building, not a half new-build.”
Interiors
There was, amazingly, only one stair in the original building, but the architects exploited a vast redundant brick-built malt kiln in the centre of the masterplan as a striking circulation and reception befitting the new use. The retained kiln has a capacious pyramidal roof and extends the full height of the building, interconnected with the different levels, so “in terms of access, it ticked all the boxes.” It was a major operation to repair and clean the interiors of the kiln but it delivers an imposing entrance, enhanced by the dark steel stair and lift core, an original iron column, and some large pieces of factory machinery on display. It is an airy space (partly from the fact that only the enclosed reception area is heated), and a timber-lined ceiling, low lighting and unfinished walls increase the sense of theatre, while tying into the lean approach taken elsewhere in the design.
In the tenanted workplace areas, walls are limewashed, but their original character strongly remains. Comfort is increased, alongside the natural ventilation and largely natural lighting, but the fabric is insulated reflecting the fact that tenants are paying for the space. In the first floor, which the architects fitted out, there are a row of enclosed glazed offices, but there is the possibility for cross-ventilation across the whole space. Greensmith says: “We enjoyed this opportunity to challenge the brief and look at whether we could avoid generic new build solutions, this was the opportunity to ‘zoom out’ and take a pragmatic and logical view on where to spend the money.”
Programme & build
On the ground floor is the museum, which tells the story of the mill’s role in the Industrial Revolution as well as in subsequent world architecture, including an original iron truss on display, along with a cafe open to the public. Above are four floors of flexible office space that will provide accommodation for around 360 people. There is also circulation and meeting space within the kiln for commercial tenants, as well as access for visitor tours to the restored Jubilee Tower.
“We pushed for public access to all the ground floor buildings,” says Greensmith, as part of meeting the client’s goal of increasing engagement. The open circulation space provides routes through the buildings, and views in: “It’s wonderful, the kids coming home from school take a short cut through the site.” In addition to using the ground floor cafe and museum to bring in people and revenue, guided tours are held to the top of the timber tower to survey the whole site and far beyond.
He says that the challenge of navigating between heritage and commercial considerations in terms of the workplace floors focused around potential subdivision of floors, as “post-Covid, people don’t want to work in big open plan floors.” He says that the designers “always knew we needed a mix; including smaller units for SME and innovative start-up businesses.” He says that with the third floor having a central line of beautiful forked iron columns (the fork originally held the mill drive shaft), the architects were trying hard to retain it as open plan. Where more structural strengthening was needed, a more compartmentalised approach was used.
The contractor did a lot of the work themselves rather than subbing it out, with individual staff a regular sight on the project over several years. Many of the materials and trades were sourced locally; the roof slates came from Wales, and many of the replacement bricks from Gloucestershire-based Northcot Brick. A lot of the joinery and metalwork repair was done by local firm Heritage Project Works, and the goal was “about leaving a building which could be maintained by the local industry, rather than importing things that would need to be rethought in 10 years,” says Greensmith.
The first floor of workspace was fully fitted out by the architects, to set the standard for subsequent floors above, showing “how to keep views open, and how to create communal and breakout space.”
Conclusion
The workplace levels of the project are now potentially around 75% let (the fully let first floor is being followed by the second which is currently being fitted out, and the fourth floor negotiations were close to conclusion). Tim Greensmith says that “you hope it now has the critical mass that people will be fighting over the last areas.”
There are other buildings available on the site which can be converted if required, part of the adaptability of this historical antecedent of 20th century construction. This re-use of the structure shows the flexible qualities which are inherent to the building, and which have been harnessed by the architects to provide a commercial boost for Shrewsbury in future decades. Doubtless in planning a mill 225 years ago which would make work less of a threat to life, Charles Bage could not have envisaged that his functional frame of slender iron columns, built for workers’ safety, would be preserved for a much less intense long-term use, as a home for small businesses.
Beyond the retention and protection of an important architectural monument with an uncompromising attention to quality however, perhaps the real importance of this project is as a vivid demonstration of why and how an entire high-profile building of this scale and nature can be saved, and given a sustainable new life.
Project factfile
- Architect: Feilden Clegg Bradley Studios
- Client: Historic England
- Contractor: Croft Building Conservation
- Structural engineer: AKT II
- GIA: 9000 m²