Material Marvels: Shrewsbury Flaxmill Maltings – The grandfather of skyscrapers

Materials World magazine
,
27 Feb 2019

Shrewsbury’s flaxmill is recognised as the world’s first skyscraper, influencing architecture globally with its innovative iron-frame construction. Shardell Joseph looks into its history and plans for its restoration. 

Shrewsbury Flaxmill Maltings in Shrewsbury, UK, is not only the earliest surviving entirely iron-framed building in the world, but it is also internationally recognised as the first ever skyscraper, laying the foundation for the many iconic skyscrapers to come.

Constructed in 1797 under the name Ditherington, the mill remains significant in the history of engineering, and is rich in social, economic and technological importance. Named ‘the grandfather of skyscrapers’, the site showcases the development of techniques in metal framing, an accumulation of heritage and holds unique research and learning resources for engineering and architectural historians worldwide.

Calling it the ‘most important building of the modern age’, Historic England is restoring the flaxmill to revitalise the five-storey building using new materials and methods to reinforce elements of its structure, while respecting its original iron-framed architecture and the materials used.

‘The incredible thing about it is, it’s a remarkable survivor at the end the day and it really was a quantum leap in terms of use of materials’, says Historic England Project Lead Alastair Godfrey. ‘As a prototype, it was right at the edge of technology at the time, and it’s an absolute miracle the building still exists.

‘And now, skyscrapers are a global phenomenon – you’ve got New York, you’ve got Chicago, Detroit and all these places – their DNA for the technology in those buildings all comes back to this one mill.’

History of Ditherington mill

Known for having a network of local innovators and free thinkers, it is not particularly surprising that the world’s first iron-framed building was constructed in Shropshire. The industrial revolutionaries in the area had pioneered new uses for iron before the flaxmill, which included many other world firsts, including an iron bridge, boat, railways and even an iron aqueduct at Longden-on-Tern on the Shrewsbury canal.

One such iron pioneer was local surveyor and wine merchant Charles Bage, who designed the five-storey main building of Ditherington flaxmill – the centre of a larger complex that developed until 1812, on the northern outskirts of Shrewsbury. Fascinated with the properties of iron, Bage brought forth the cast-iron frame as a solution to the problem of textile mills burning down – a pervasive issue in the 18th and 19th centuries, which caused losses of life, affected production and capital, and steeply increased insurance premiums. Early mills were huge fire hazards, as they often contained wooden machinery coated with flammable lubricants – commonly, whale oil – and were dusty environments with lots of textiles and open flame rush lights and candles.

‘If you’re producing something like flax, it produces an awful lot of waste material which is very dry, powdery and will only take one person to knock over candle and the building goes up,’ says Godfrey. ‘It’s like a tinderbox in effect – the whole thing goes incredibly quickly.’

To gain knowledge of iron and its fire-resistant properties, Bage corresponded with engineer and architect William Strutt, who was the first to use iron components as a means of making textile mills fire-resistant. To do this, Strutt used brick arches sprang from substantial timber beams, supported by cast-iron columns with the unbalanced horizontal thrusts restrained by wrought-iron tie rods.

Bage was also acquainted with William and Joseph Reynolds of the Ketley Ironworks, and Thomas Telford, who were regarded as pioneers of iron construction in Shropshire. While Ditherington Flaxmill was under construction, Joseph Reynolds passed Bage test results of the structural properties of iron carried out during the design of the Longdon-on-Tern aqueduct.

Its iron upright columns and iron cross-beams were cast at the foundry in Coleham, Shrewbury, by English ironmaster William Hazledine. As the owner of ironworks, mines and quarries throughout the district, Hazledine supplied ironwork to Scottish civil engineer and architect Thomas Telford for the Pontcysyllte aqueduct bridge and the Menai suspension bridge.

Once completed, Ditherington Flaxmill was the most advanced factory of its age, making use of steam and not hydropower, so did not need to be located in a remote rural river valley. Its use of gas lighting enabled 24-hour working and would have amazed local residents when light blazed from its windows at night. Incorporating gas lighting at the mill, some years before houses in Shrewsbury were lit in this way, also sheds light on the significant technical, economic and social impact of the building.

‘It was certainly one of the world’s first artificially lit factories […] London didn’t get gas lighting until 1815. You can only imagine how astonishing it would have been to see this light which also meant people could work longer hours,’ says Godfrey.

During the Industrial Revolution, the new spinning mill quickly became Shrewsbury’s largest employer with more than 800 men, women and children working there manufacturing linen thread from flax. Despite being ‘the largest firm of flax spinners in Europe’, the mill still suffered financially, and eventually closed its doors in 1886.

Purchased by entrepreneur William Jones, it re-opened to produce malt for the brewing industry under the new name of Shrewsbury Flaxmill Maltings in 1896. He adapted the the buidlings for malting, adding the massive malt kiln at the northern end, and replacing the boilers on the eastern side of the main mill with a single-storey  structure, extending the area for floor malting.

Later, part of the building served as a barracks for soldiers during World War II, and it finally shut its doors as a maltings in 1987. Since then, it had been left unused and suffered damage by vandalism, until it was bought by Historic England in 2005, which began restoring the building in 2015.

Restoring an industrial treasure

Historic England has made a major step in the restoration of this historically and architecturally significant building. Listing the main mill as a Grade I – one of the most imperative buildings in English history – Historic England has committed to urgent repairs with its own funds combined with a £20.7m grant from Heritage Lottery Fund.

So far, the roof has been restored with materials matching those of its original construction. It took around 15,000 new Welsh slates, which came from Penrhyn quarry – the only remaining source of North Wales slate.

The saw-tooth profile with 17 valley gutters between the slate roof slopes gives the roof a noticeably unusual design. When the roof covering was stripped, it was discovered that the original cast iron of 1797 still survived. Each section of thick cast-iron was 4m long and extremely heavy, which required four men to lift it. To repair the roof, five new sections of cast-iron gutters to match the original had been specially made at the Barr & Grosvenor Foundry in Wolverhampton.

Friends of the Flaxmill Maltings Chair, Alan Mosley, said, ‘It’s fantastic to see the new roof in place and that it has been restored so sympathetically, using Welsh slate as it would have had when it was first built.’

The next step for Historic England is to replace the damaged building bricks. Provided by traditional brick manufacturers Northcot Brick, Historic England has commissioned 30,000 special sized bricks called ‘great brick’ – approximately one-third larger than the standard. These bricks were manufactured at the end of the 18th Century by Shrewsbury developers because new buildings were taxed to raise funds for wars in the American colonies. Buildings would be taxed per brick, so using larger ones helped reduce the number  required, and consequently the amount of tax.

Testament to the building’s innovative architecture and fireproof properties, the cast-iron frame requires little-to-no restoration work. The original design of the cast-iron was constructed in the shape of a cruciform to fully use the strength of the material. Some of the major challenges at the time were getting a consistent mould and strength to the metal, which can result in fractures. The cruciform shape allows for the structure to cool and solidify with greater and more consistent strength.

‘The amazing thing is we’ve had to do nothing to the cast-iron frame,’ says Godfrey. ‘When you go on site and we expose some of them you can actually see that the pouring marks where the iron was poured into the sand mould.

‘Along with this cruciform shape, cast-iron has an incredibly strong compression, and you’ve got cast-iron columns, beams and tie rods which create this three-dimensional frame with brick jack arches in between, so you’ve got a single skin of brick that arches, which gives the fireproofing between the floors.

‘The melting point of cast-iron is about 1,200 degrees centigrade so you know you’re going to have to have a pretty ferocious fire to damage that frame.

‘The fact that the frame is unrepaired is remarkable. ‘They didn’t have the structural engineering calculations that we know today. Because they couldn’t work out mathematically the strength in the bends of cast-iron, the first thing they did was build a scale model of the building and loaded it until it collapsed and then scaled up that model to create the full-size frame.’

Work needed on the cast-iron frame will only involve stripping it down and encasing it with intumescent paint to comply with modern building regulations. This fireproof paint will be used as a passive fire resistance measure, so when the frame is exposed to heat the paint will expand in thickness, acting as an insulator that keeps high temperatures away from structural members or protected openings.

Flax future in Shropshire

Historic England recognises Shropshire’s pivotal role in leading the UK’s Industrial Revolution, and plans to restore the flaxmill in an effort to drive the town’s renaissance as a regional economic hub. Once restored, Shrewsbury Flaxmill Maltings will serve both historical and commercial purposes, contributing to the growing creative industries of the region, which has been referred to as the Silicon Valley of its age.

‘This moment, seeing the scaffolding coming down and the original roof completely restored, is a significant milestone in the project to restore Shrewsbury Flaxmill Maltings. The sensitively renovated building will create a much-needed hub for the area of industry, learning and creativity,’ said Historic England Chief Executive Duncan Wilson.

Historic England plans to open the buildings doors in August 2021.