The Engine Shed Restored

The Engine Shed in ruins (2014)

In 2012, after over a decade of abandonment and slow decay, the Engine Shed was offered a new lease of life. After the closure of the Avon factory the Nunn Mills site became part of what the local authority called the Northampton Enterprise Zone. the University of Northampton entered into negotiations with Avon and developers Taylor Wimpey and Persimmon regarding the acquisition of   57.65 acres of land on what is now known as the Waterside Development that would see the establishment of a Campus that will enable the University to transform into an internationally facing University committed to delivering outstanding life-changing opportunities in education, underpinned by a culture of entrepreneurship, purposeful research and social enterprise recognised around the world for its originality and impact.

The office covered in ivy (2014)

At this stage the area was so overgrown with weeds that nobody knew the office building was still standing and the Engine Shed itself was just a shell. Following initial considerations regarding the Engine Shed’s use as a gym or administrative offices, the Students’ Union identified the opportunity for the building to become the centre for its on-campus services. To realise this aim the Students’ Union applied to the Heritage Lottery Fund for a grant of £1,323,300 to help restore and refurbish the building and create meaningful projects to help both students and the local community engage with the history of the site.

The shed after the weeds were cleared

After the site was cleared of weeds it was assessed for structural integrity and historical evidence by specialist heritage architects Purcell. Architects Moses Cameron Williams then produced plans for the Students’ Union which would not only provide a functional space for the organisation, but also respect the heritage of the Engine Shed. This included the removal of the later extensions and additions to the building, such as the welding booths and store rooms and concrete platform which were associated with the welding school.

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Architectural plans devised for the Engine Shed in 2016,

Unfortunately, the weeds which had taken over the Engine Shed had done considerable damage to the brickwork. This vegetation had to be carefully removed to limit the further deterioration of the brickwork. The top courses of the walls had to be removed completely and relayed with reclaimed bricks. Detailed surveys were drawn up of every single wall, which the conservation architects used to guide how each piece should be treated. This included removing algae, mosses, paint and grease stains from all the bricks. The interior of the shed had layers of whitewash and graffiti which required careful removal to expose the natural colours of the brick beneath.

Detailed assessment showing the damage to one bay of brickwork
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Brickwork in the process of cleaning

The original roof of the Engine Shed was a slate tiled roof with a ‘clerestory’ design which provided vents for smoke and steam to escape along the length of the building. The roof was supported by an elaborate framework of wooden and cast iron trusses. This roof was replaced at some point between 1939 and 1963 with one made from corrugated asbestos. By this stage the Engine Shed was no longer servicing steam trains, and therefore did not require such an elaborate roof. The original framework was kept however. The fire of 2000 completely destroyed two of the trusses at the entrance to the shed. The weight of the roof collapsing also warped the next four trusses beyond repair.

The poor condition of the roof before restoration is evident in this photograph (2014)

It was decided that the new roof should be built in the ‘clerestory’ style in order to restore the Engine Shed to its original appearance. This meant that in total six trusses needed replacing in a style compatible with the originals. Surveys of the original roof trusses provided something of a puzzle, as our engineers could not work out how the Victorian structure actually bore the weight of the roof. It was therefore decided that rather than directly replicate these trusses, it would be more appropriate to produce a new design which matched the look of the originals, but was guaranteed to be structurally sound.

Design concepts for the new roof trusses (2016)
Inside the new roof

Much like the brickwork, the windows of the Engine Shed are a key part of its architectural heritage. A common feature to Midland Railway buildings was the use of blind arcading along the length of the building. This is an architectural term meaning the use of arches without openings as a decorative feature. To complete the look the builders installed elaborate iron framed windows incorporating diamond and lozenge shapes. Although these original frames were still in place when the Union took on the building, they were in a delicate state. Despite metal security grills being placed over the windows when the welding school occupied the building, most of the original glass had been shattered by vandals. All of these frames needed to be carefully removed so that they could be restored by a specialist firm. Several of the frames were so badly damaged by the 2000 fire that they effectively disintegrated. New frames were cast from the originals to replace these.

The removal of the windows for restoration

When it was first built the Engine Shed had large wooden doors mounted on large hinges, these would have been open all day when locomotives were being serviced, but closed at night for security. These doors were altered after the shed was converted into a workshop after 1924. The northern entrance was bricked up, with a pedestrian access door, whilst the southern entrance was retained to allow wagons to enter the workshop. This was later replaced with a metal roller shutter when the Welding school took over. The brick wall was completely removed to open up the northern entrance. The original plans were to recreate the original shed doors and hang them from the existing iron hinges; however these proved to be too unstable for the new doors, which weigh approximately two tonnes. A new frame therefore had to be installed to accommodate the new doors you see today.


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The Northern pit is exposed during the removal of the floor (2016)

Although it was always understood that there would have been inspection pits in the Engine Shed, it was always assumed that these pits would have been destroyed when the concrete floor of the Welding School was laid in the 1960s. However when this concrete floor was removed as part of the renovation works, the pits were found to be intact. These pits had to be fully excavated and surveyed for the purposes of the Historic Building Record, before it could be decided what to do with them. Research showed that when the Engine Shed was converted into a workshop in the 1920, the northern line was removed and covered over. The Southern line was kept however, so that wagons could be repaired.  This meant that southern pit was remarkably well preserved; the rails were still in place, having been incorporated in the welding school’s concrete floor, the track chairs and cap-stones were also in excellent condition.

This image demonstrates the difference between the two pits. The northern pit (right), being in a worse condition than the southern (left)

The northern pit however was in a poor condition. The rails and cap-stones were missing and the brickwork was badly damaged. It was deemed that, although the pits were of historic value they would have to be re-covered for construction of the Students’ Union to continue. This meant that the pits had to be refilled in a manner that protected them, but could be easily reversible if they needed to be opened up again. As a result the pits were lined with a fabric membrane, then in-filled with rubble before the new concrete floor was laid with the original rails set into the concrete.