Velvet Mill – A Building Fit for a City of Culture

Now just a week away from AJ Retrofit Live, a new event from the Architects’ Journal celebrating and championing retrofit projects across the country, today we’re exploring Bradford’s Velvet Mill. As part of our ‘My Favourite Retrofit’ campaign, our Regional Director, Martin McGovern walks us through Lister Mill’s Velvet Mill…

By the year 1900 there were 350 spinning mills in Bradford, responsible for two thirds of the UK’s wool production and processing.  The deindustrialisation of the north and global competition led to the steady decline of the textile trade and of Bradford as a major industrial hub.  Today the number of working mills can be counted in single figures.  A legacy of this era is a rich array of fine Victorian mill buildings.  Arguably the finest in Bradford and certainly one of the biggest in the world was Lister Mills.  In the heart of the Manningham area this beautiful campus of buildings stood derelict for almost 40 years prior to its purchase and transformation by Urban Splash.

Much of the original weaving sheds and support buildings have been lost to decay but two of the finest buildings remain.  The Silk Warehouse and Velvet Mill were beautifully refurbished and successfully converted to residential apartments. As a young engineer I was fortunate enough to work on the conversion of Velvet Mill, working closely with a talented architect and given the responsibility to lead the engineering and influence the redevelopment of a significant piece of national history.

Given the opportunity to wander around this empty building, often alone – perhaps in hindsight not such a great idea – to get to understand its details and curiosities was a privilege.

The Velvet Mill was constructed around 1860 using techniques familiar at the time including load bearing masonry facades and a cast iron frame of beams and columns with jack arch floors spanning between the cast iron beams. Jack arch floors were constructed not in brickwork as was typical at the time but using an early form of concrete known as Dennett’s Concrete, a gypsum based product that has the rather unhelpful property of losing strength when wet. A condition which, in many places, required one to traverse the building along beam lines much like a trapeze artist on a high wire.   Thankfully this is a condition reversed upon drying.

An assumption often made when converting mill buildings is that the original floors were designed for heavy industrial loads and that the loads associated with conversions such as offices or domestic flats are less, therefore introduce no particular challenges.  This may be the case where said buildings were used for heavy industry or warehousing, such as The Silk Warehouse, but a lot of the mill stock was used for weaving and the loads associated with timber looms aren’t as high as one might have thought – think timber tables and chairs.

The replacement of original stone flags, most of which had been long since robbed, with  a concrete slab for fire resistance and robustness, in conjunction with the increase in live loading associated with the conversion to domestic dwellings, did result in a net increase in load that in some cases required significant structural analysis to justify no intervention while in others, resulted in the sympathetic introduction of additional structure or some clever composite action to carry the increase in load. Having a leading role in the final details with the architect is something I recall fondly.

There are great examples where the original jack arch floors have been stripped out full height of the building, forming staircases and atrium exposing the original asymmetric cast iron beams with their bulbous flange toes and the ornate column heads.  I like to think that these details will be around in another 150 years and a young engineer or architect of the future will be as fascinated as I was.

The most visible intervention in the building was the introduction of the duplex pod apartments on the roof.  A beautiful piece of architecture, the form of which was inspired by the braiding of the wool produced in the building, required the loose filled cavity walls to be pressure grouted to carry the additional two storey loads which get to the perimeter via a single span 20m fabricated transfer beam.  This is the crowning glory of the building visible from all of Bradford and affording views to the Pennines.

Announced as the UK City of Culture for 2025, the regeneration of Bradford continues to have an exciting and significant impact on the UK’s youngest city. If the redevelopment of Lister Mills demonstrates anything, it is that in these carbon conscious days we already have a wealth of beautiful historic mills just waiting to be brought back to life and benefit the community of Bradford.