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CoRE, Stoke-on-Trent, PRP Architects

CoRE A derelict pottery works is being rebuilt as a college dedicated to excellence in refurbishment, writes Martin Spring

In Stoke-on-Trent a small cluster of brick-built, Victorian-era bottle kilns poke their chimneys out of a derelict pottery works, which is about to be redeveloped to become the UK’s one and only Centre for Refurbishment Excellence.

Construction started earlier this month at the former Enson Pottery Works, which will soon house a 6,000m² national venue for teaching, exhibiting and researching sustainable refurbishment and retrofitting. What is more, the conversion itself is to be conducted as a live demonstration project for the education courses it will provide.

That, at least, was the worthy and topical intention. But, in the event, when PRP Architects came to survey the derelict buildings, they found several had deteriorated too far to save. Of the three main buildings on the site, only one was deemed worthy of conversion. Fortunately, this was the largest block, containing three of the bottle kilns. It will serve as a conference and exhibition centre above educational workshops.

The second-largest block will be demolished and rebuilt as a refurbishment training college. More questionably, a Victorian corner pub will also be demolished, but rebuilt in facsimile as a sham refurbishment demonstration building. Although listed Grade II, the industrial buildings on the site were developed piecemeal over more than a century in a mish-mash of different sizes, forms, materials and styles. Encouraged by English Heritage, PRP intends to keep the site’s raw industrial character, both in the retained and the new buildings.

The new three-storey college sits on the same footprint as the building it replaces. That leaves a convivial, wedge-shaped courtyard between it and the retained building, where students can erect and exhibit construction mock-ups.

Sadly, the idea of converting the three brick kilns into habitable spaces, along the lines of, say, windmill conversions, was a non-starter. ‘They are more like chimneys than windmills,’ says PRP director Frances Chaplin. Having absorbed decades of intense heat, smoke, salts and, latterly, rainwater, the kilns could not be made serviceable without an intrusive protective layer. Entry to each one is through a hobbit-sized shutter measuring 700mm by 1.5m, while its solid concrete floor is shaped into a mound.

So what to do with the kilns? ‘They were built to retain heat, so we thought it would make sense to keep them for heating and cooling,’ says the project architect, Fiona Sadler. Under the refurbishment each will serve as a plant room and plenum for exhaust air, which will pass up a flue fitted within the original chimney, through a heat exchanger and out through louvred vents just below a new chimney cap.

The brick cylinders of the three kilns, with their encircling iron reinforcement bands, will stand as sculptural set pieces within the converted block, which was mostly built in the 1950s. The upper floor will be minimally refurbished and left largely open-plan as, in Sadler’s words, ‘a blank canvas, with the flexibility to hold conferences, talks, exhibitions and other events’. The ground floor will be converted into educational workshops for the college.

To attain BREEAM Very Good standard, the original brick walls and flat roofs will be lined with insulation. A variety of insulations will be showcased, including cutaway sections, says Sadler. The original Crittall steel windows will be replaced by the same company’s matching new double-glazed model. But secondary glazing will also be needed to compensate for the cold bridges of the steel frames. English Heritage did not want any secondary glazing frames to be visible, so it will be virtually frameless, while ventilation will be mechanically supplied via a heat exchanger.

The three-storey new build college will contain classrooms, staff offices and a refectory, while the workshops will be offloaded into the converted block. The college is the first phase of the entire project, and the offloading resolved a budgetary dilemma caused by the college increasing its accommodation brief while the grant promised by the Department for Children, Schools and Families stayed fixed.

Despite a low budget of £2.3 million, the 1,350m² new build college attains BREEAM Excellent standard. This is achieved through a combination of a highly insulated building envelope, exposed soffits of concrete floor planks, mechanical ventilation with heat recovery, air-source heat pumps and 200m2 of photovoltaic cells on the flat roof, which will generate 30kW of electricity at peak.

The entrance foyer and main stairs of the college will remain unheated but, since they face south through full-height window walls, these spaces will be sun traps.
Finally, the new build and converted blocks will be linked by matching, bronze-coloured brickwork. In homage to two local traditions - brick-making and pottery manufacture - the college walls will be speckled with glazed bricks.

In September this year, this abandoned pottery works will be reborn as the national Centre of Refurbishment Excellence. Then it will be down to its new occupants and their new facilities to lead the local economy and the nation at large out into the sustainable world of building refurbishment and retrofitting.

What is CoRE

The UK’s first Centre of Refurbishment Excellence (CoRE), which started construction this month in Stoke-on-Trent, has a big agenda. It has set its sights on the government’s commitment to slashing carbon emissions by 30 per cent by 2020 and by 80 per cent by 2050.

CoRE sets itself the task of training a workforce skilled enough to tackle this sustainable retrofit challenge. As well as construction training for 14 to 19-year-olds, it intends to ‘deliver bite-sized packages of learning’ to small and medium-sized contractors to enable them to bid for social housing contracts. More than that, the centre will exhibit and demonstrate innovative products and techniques of sustainable refurbishment.

The centre is developed and run by Stoke-on-Trent city council, helped by a £3.5 million grant from the European Regional Development Fund. But the real instigator and champion of the project, according to Frances Chaplin, director of CoRE’s architect, PRP Architects, is the Building Research Establishment. BRE and PRP Architects have previously undertaken a similar £2.7 million carbon-reduction retrofit of a Victorian stable block at the BRE’s premises in Garston, Hertfordshire.

Credits

Client Stoke-on-Trent city council
Architect PRP Architects
Structural engineer ABA
Services Engineer Gifford
Design-and-build contractor Shaylor Construction
Predicted annual CO² emissions 18.6kg/m²

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