Wrought iron struts in a dye house roof.
A close-up of the ornately designed compression struts from the Dye House at Shrewsbury Flaxmill Maltings. © Historic England

The Dye House

5 May 2022

The Main Mill at Shrewsbury Flaxmill Maltings is world-renowned because of the use of iron in its construction and the impact that this had on skylines around the world. However, it is not the only building of interest on site. Another building with an interesting story to tell is the Dye House. 

The exterior of a brick building with writing on the wall reading: William Jones & Son.
The surviving 1850’s Dye House with maltings-era hoist towers. © Historic England

The story of the Dye House

The Dye House that exists today was built in 1850 and replaced a smaller structure dating back to 1804. The purpose of the new, larger Dye House was to help with the flax mill’s increasing focus on dyed linen products. The aim was to compete with linen products from Ireland and Scotland, and cheaper cotton products, by simplifying production and removing duplication of effort between the other mills owned by John Marshall in Leeds and Shrewsbury.

When comparing it to the earlier flax-era buildings, the amazing advances in iron-framed construction can easily be seen when you take a good look at how the Dye House was made.

The 1797 Main Mill has a frame constructed from cast iron columns and beams, but the Dye House uses a different iron structure in its design. 

The evolution of iron

Using iron for building frames was more common by 1850.  By this time, wrought iron had become a viable building material as well as cast iron. Although cast iron is strong and less likely to break if it’s pushed together onto itself (compression strength), it is brittle and fractures if there is significant force or pressure in a direction which may force it apart (tensile strength). Wrought iron bends rather than fractures under tension but it is not as strong as cast iron if it is compressed.  The different properties of these two types of iron is why both were used in the construction of the Dye House.

Featuring a lightweight wide-span roof of Welsh slate with ridge roof lights, the Dye House boasts one of the most sophisticated roof designs of the mid-19th century, combining the benefits of both wrought and cast iron.  Together they made for a stronger and more durable structure.

A roof made with wrought iron struts.
The large amount of light let in by the roof design can be clearly seen here. © Historic England

This type of roof design had been used before in other smaller textile mills, as well as in new types of structures, such as train stations.

A perfect example of form meeting function, the ornate design of the compression struts in the Dye House roof are more than just decoration. Empty space left by this style reduces the weight of the roof while also ensuring its strength and resiliency. 

The roof rafters are bolted to cast iron valley gutters mounted on columns, which enabled the construction of a large and unobtrusive roof design, which was perfect for letting in light to aid the workers.

Wrought iron struts in a roof.
A close-up of the ornately designed compression struts from the Dye House at Shrewsbury Flaxmill Maltings. © Historic England

Linen dying

The process of dying linen meant that dye houses were damp and humid. This presented a difficult problem for traditional wooden buildings which need drier conditions to keep the wood in good condition. Humidity was caused by the large dye vats which were used to dye the thread with natural dyes, vegetables and mineral compounds.

A stock book from the flax mill dating back to the 1820’s refers to natural materials being used to colour the linen thread, including indigo (which makes shades of blue), sumac (which makes a pink-red shade from the fruit or tan and light brown shades from the leaves) and logwood (which makes a rich, deep purple and was also often used as base for making black).

The 1850 Dye House was constructed with an iron frame rather than being built of wood. Also, instead of nailing the roof slates to wooden laths, they were secured with wire to the iron battens, which gave more protection from the humid conditions. These innovative designs helped the Dye House to withstand the problems presented by such a damp environment.

New use and decline

After Marshall’s flax business closed in 1886, the site’s story almost ended, but then a wealthy maltings baron named William Jones bought it and put it to new use.  A number of changes and alterations were made to the old flax-era buildings and new structures were added, making the site fit for its new purpose.  When it re-opened around 1897-8, after being closed for a decade, the site began producing malt for the brewing industry.

The former flax mill was ideal as a maltings because the large floorplates of the Main Mill and Cross Mill buildings gave the space needed for laying out barley grain so that it could germinate, which is a crucial part of the malt-making process.

This massive change in role for the site meant that the Dye House become a space where the barley grain that was arriving on site was cleaned and dried. Hoist towers were added to the building to help lift the grain from a newly constructed railway siding and new machinery was installed.  After the barley had been cleaned and dried in the machinery, it was put into bags before being moved into the other buildings on the site for laying out, so that the germination process could begin.

The site continued as a maltings until 1987 when that business also closed and the buildings fell into disrepair. Historic England bought the site as buyers of last resort in 2005 and are now leading the site’s regeneration.

The future of the Dye House

The future of the 170-year-old Dye House remains unwritten. 

The restoration of the Main Mill and Kiln is taking place supported by a £20.7 million grant thanks to National Lottery players through The National Lottery Heritage Fund, combined with the additional funding from the Marches Local Enterprise Partnership via its Growth Deal with Government, and from project partners Historic England, Shropshire Council and the Friends of the Flaxmill Maltings. 

During the restoration the Dye House has been host to lots of community activities. Events such as family fun days, exhibitions, school visits, workshops and training have all been held in the Grade II* listed building, welcoming people from far and wide to the site and sharing the story of Shrewsbury Flaxmill Maltings with them.

Once the current project phase is complete, Historic England will continue to look for funding to give the Dye House and the three other unrestored historic buildings a new lease of life, ready for a third century of use.

Inside the unrestored Dye House. © Historic England

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