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The UK's oldest gunpowder mill gets the office treatment Overhead view of the staff canteen. On the right the glazed meeting room projects into the communal space Sunlight floods in through the Gunpowder Mill’s clearstorey The original Water Tower stands alongside the glazed new build Horizontal louvres prevent the building from overheating in summertime Diagram detailing how the different elements of the project fit together
12 Mar 2010

Hill Partnerships HQ by PTEa

Words by  Photo by Hill Partnerships and PTEa
  • Architect: Pollard Thomas Edwards architects
  • Client: Hill Partnerships
  • Location: Waltham Abbey, UK
  • Cost: £6.8m
  • Duration: January 2008 - July 2009
  • Floor Space: 4,500 sq m

PTEa contends with deer and newts to create a stellar revamp of an 18th-century gunpowder mill  

There’s an almost irresistible temptation when writing about an office in a former gunpowder mill to crowbar as many bomb metaphors in as possible. So here goes. Kaboom! London-based practice Pollard Thomas Edwards architects has created an explosive new HQ for affordable housing specialist Hill Partnerships that is pure dynamite. (That’s enough, Ed.) Nestling in a strip of greenbelt land near Waltham Abbey between two SSSIs (Sites of Special Scientific Interest) and adjacent to the River Lea, it’s the sort of location that comes along once in a blue moon.

Drenched in history, the site dates back to around the 1730s, when it was the largest gunpowder works in Britain remaining in use as a research centre by the Ministry of Defence until 1991. The driving force behind the project was Hill Partnerships’ supremo Andy Hill. Until then the company had been languishing in a business park in not-so-glamorous Chingford, and Hill was desperate to make the Gunpowder Mill his new HQ.

The question was, which architecture practice could step up to the plate? One glance at PTEa’s own nerve centre, a listed Victorian wharf converted by the practice, convinced Hill he’d found his answer. The scheme wasn’t exactly a cakewalk though. Evoking an era of piracy, cannonballs and pantaloons, the ageing buildings were steadily being reclaimed by nature, the creeping greenery only serving to enhance the general eeriness.

“I was very taken with the atmosphere of the whole place,” says PTEa’s project architect Andrew Stokes. “It’s very quiet. When I went down on site it was so overgrown and suddenly this enormous antlered deer charged out of the building.” The mixture of canals and woodlands meant the dream site could quite easily have turned into a nightmare.

The practice spent a good deal of time negotiating with environmental agencies over the protection of newts and other aquatic beasties. Similarly, night-time illumination had to be restricted to prevent errant bats from crashing into the building. “When we approached the scheme we really wanted quite a light touch,” says Stokes. “It was key to find a balance between that beautiful landscape and the atmospheric buildings.”

The task PTEa was charged with was not merely a restoration job. The site broke down into three separate structures: the Powerhouse, the Lodge and the Water Tower, disparate elements that had to be pulled together. The Lodge, a Grade II-listed building, was the most straightforward. The building was already in use by the trust as an archive and office, but needed a revamp.

Standing imperious in the north of the site, the triple-gabled Powerhouse comprised two halls, including an elongated shed known as the Engine House. Protruding from the main cluster, this elegant structure, with its magnificent glazed clearstorey, became the scheme’s nucleus.

“What was fantastic was this sense of space and light,” says Stokes. “It is a triple-height space, but the idea was to retain it as a single volume.”

To make this happen, PTEa inserted a number of gangways and meeting pods recessed from the envelope of the building. Directly above the entrance behind a glass wall rests a large boardroom, cunningly placed to avoid interfering with the openness of the space.

In an appreciative nod to the elegance of the original steelwork, the two-tier levels are accessed by a folded metal-plate stair. Further realisation of the building’s rich heritage is detailed by a refurbished crane mechanism that hangs over a walkway. PTEa took great care not to pass off its modern interventions as original work, painting the newer work a different shade of grey to the old.

“Night-time illumination had to be restricted to prevent errant bats from crashing into the building”

“We are architects, after all,” says Stokes, acknowledging his profession’s penchant for all things ashen.

The ground floor is given over to the reception and at the back staff can mingle in the canteen. In the adjacent double-bay Boiler House, space was created for two new floors by reducing the foundations.

Due to the flood plain, this was potentially a rather soggy banana skin. However, careful calculations with the environment agency showed that PTEa could dig down half a floor without the staff needing waders.

Open-plan workspaces take up the building’s centre, while along the partitioning wall sit single person offices. A small meeting room features a flat-metal bay window that projects into the neighbouring Engine House.

The offices are furnished with all the mod cons expected of a building short-listed for a BCO (British Council for Offices) award – acoustic ceilings absorb any racket and insulated white plasterboard walls proffer a pleasant working environment. The two buildings are connected by staggered bamboo walkways that extend through into the new build on the far end of the site. Sidestepping pastiche was essential if there was to be a coherent dialogue between the old and new sections. Therefore PTEa opted for a steel-framed glazed structure contrasting radically with the original brick.

“We felt it should be contemporary,” says Stokes. “These are the old buildings and these are the new.” According to Stokes, the key thing was to avoid the old and new “crashing into each other”.

To solve this problem glazed junctions were cut into the brickwork ensuring it remained visible while simultaneously providing a subtle separation.

A large glass box is great for tomatoes, but less than ideal when tackling the age-old solar gain conundrum. So to prevent the occupants from cooking at their desks, PTEa introduced timber louvres set into galvanised steel frames, which also disguise the presence of the fire escape. Connecting the new section stands the Water Tower, housing three floors of office space with a boardroom at the pinnacle.

In keeping with the restoration work elsewhere on the building, the original vertical glazing was reinstalled into existing recesses in the brickwork.

“There had been a lot of work done on the building that detracted from it over the years,” says Stokes. “Some of the bays of the building had been blocked up. Where we could we reinstated the natural rhythm of the building by retaining all old brick arches and rebuilding the ones that had been lost.”

In an area of outstanding natural beauty, PTEa was keen to ensure the building was not only as environmentally friendly as possible but also protected the habitat of indigenous species.

To this end, the practice constructed a floating boardwalk over the reed beds that encircle the site. Wrapping around both the new and existing buildings, the path feels a little reminiscent of a nature trail. It’s fair to say sustainability wasn’t such a big deal 300 years ago, so to reduce the Gunpowder Mill’s carbon footprint a cocktail of measures were introduced. Photovoltaic tiles were incorporated into the existing roof and the new build featured 7 sq m of solar panels. The original building is naturally ventilated and controlled by the Building Management Controls (BMC), which opens the windows at night – exemplifying PTEa’s straightforward approach.

Feedback on the project has been extremely positive, according to Stokes.

“We had a lot of discussions on how the new office can help them find new ways of working. In the old building you never used to see people. Here everyone has to move through the building. It has changed the way the company interacts and made them feel quite buoyant about themselves.” As Stokes rightly points out, simplicity is often complicated in architecture and this was undoubtedly a very complicated project.

However, Hill Partnerships’ forward-thinking ethos, realised through an 18th-century relic, is not only a compelling irony but an enduring testament to the skill of the practice.

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