Studio 54 Architecture has refurbished and extended the Prep School at Forest School, on the edge of Epping Forest, to deliver an additional storey, a rooftop playground, and an entirely new facade.


Director Charles Thomson talks to Claire Barton of Haverstock about wrapping a new exoskeleton around an existing building, working with Accoya, and developing a language that stands up to the scale of the campus buildings and responds to the forest setting. The pair also feature in an episode of AT Conversations, a podcast hosted by editor Isabel Allen.

Charles Thomson The project was to extend and convert a prep school, which is part of Forest School, an independent day school, which includes a boys school, a girls school, the prep school and a sixth form. They’ve about 1,400 students and a real mix of buildings. The school was originally founded in the 1840s, and there are some very fine Grade II listed buildings which sit at the heart of the campus. Since the end of the second world war, there has been a lot of new building, some better than others, frankly. The sixth form centre, by Buckley Gray Yeoman, completed in 2015, is a fine, elegant building overlooking the cricket pitch, but the whole campus gives the impression of having expanded in a slightly odd ad-hoc manner.

My son went to the school, which is why I got involved. Over the last few years, we’d done a number of feasibility studies for improving the campus. And we converted two houses close to the school to provide a new home for the warden, which released more space for teaching. So we had quite a lot of basic knowledge about the school and about the personalities.

The prep school was originally built in the 1950s as a single-storey building. It was expanded with another floor in the 1970s. In recent years, the roof had become a serious problem with regular leaks and we were asked to look at replacing it. Very quickly, the idea was floated that it might be possible to build a new floor at the same time, thus saving money on redoing the roof. We did a feasibility study in 2017, which looked at various options for extending the building. We also looked at the possibility of rebuilding the school elsewhere on the site. That turned out to be quite tricky, partly because of planning, partly because it got rid of some much-loved tennis courts and partly because it seemed to be a very costly option. So we fairly quickly reached the stage where the idea of extending the school seemed the only sensible option.


The choice of timber cladding reflects the school’s ethos and responds to the building’s location – behind a range of lime trees and on the boundary of a forest.

The building had had very little done to it for a good 50 years. The services were in a bad state, it had single glazing, poor insulation … so it was decided fairly quickly to effectively refit the whole of the existing building while we were doing the top floors. The critical issue was that it was then demanded that all of the development should be done while the school was still functioning. At the time, we thought this was crazy, partly because we were also looking at the most efficient structural way of adding another floor. And of course, the most efficient and the cheapest way of doing it is not to span an exoskeleton round the whole building, but to judiciously place new columns in the existing building so you can minimise the spans. But if the building was going to be occupied while the work was going on, there was no way that could happen. And an occupied building – particularly a school building occupied by young children – puts a huge responsibility on the safe management of the construction process. With these constraints in place, we set out a programme to try and make the building project work.

We managed to assemble an extremely good team of people, who were all very skilled and committed. I had a very good team at Studio 54, we had a very good engineer in Hardman, a very good services engineer in XCO2 and a very good quantity surveyor in Stockdale. The project was driven by a committed client, represented by the bursar and the head of the prep school. The fact that the client required a construction programme that seemed to be so fraught with problems meant that, whenever there was an issue with moving children and classes around to facilitate what the contractor needed to do, they were very, very, on board. And we had an extraordinarily good contractor, Claremont. A good team is … well, it’s crucial. It made such a difference.


The reworked building echoes the strength and scale of its brick neighbours but has as ofter feel. The timber strips increase in width from top to bottom, creating a rhythm that relates to the different floor levels and adds a richness to the facade.

Claire Barton Within the collection of buildings, it’s refreshing because it hasn’t tried to reinterpret brick. It’s introduced timber and on an interesting bit of the site where there’re some really mature trees. So it sits in the context, but is a really good interplay with the existing buildings. And I think also because it’s the prep, and it’s the littlest kids in the school, it feels more playful. It’s not quite as formidable as some of the other buildings. It’s got a really nice softness. If truth be told, it’s a little bit awkward in its context, with that sixthform centre right behind it. It creates quite an awkward space between the two, but then, having said that, you were tied into the footprint of that building, so there was never anything you could really do.

And I just love the play of timber, the use of the datums. It’s really beautiful, but it’s also born out of tying-in with all those existing levels. So you’ve used that to your advantage, but obviously it was massively tricky to do. I really loved it as a building. And when you go inside, it’s got a real great sense of calm. It’s a very peaceful building and I think that’s a lot to do with the amount of light coming in. There’s a view from every space; really huge windows.

We started at the newer spaces at the top and went down to the refurbished spaces, and even though they’re lower, it didn’t feel like they were the poor cousin of the upper floor spaces. It all felt really equitable, which I thought was really lovely. And the roof terrace … I realise that didn’t have an Location plan easy ride in terms of planning, but I can’t imagine that building without it because it’s such an amazing space. And the planting around the edge really softens the top of the building. Within the context of Epping Forest, that’s a really stunning little addition. It would have been a real loss not to have had it.


The existing building had been built as a single storey in the 1950s and extended to two storeys in the 1970s.

Charles Thomson You’ve summarised a lot of what we were trying to achieve because I think one of the questions you asked almost immediately was, “Why didn’t you do it in brick?” And of course, one of the crucial things … aside from the fact that a brick box would have looked pretty intimidating, was that we’re hanging everything off an exoskeleton, so a lightweight rainscreen seemed to be the way to go.

And then it was a question of choosing the materials. We’ve done a lot of buildings in timber in the past, but not using Accoya. We did quite a lot of research into using Accoya. It is obviously much more longlasting than conventional timber, which was a good sell as far as the school was concerned.

It’s almost too trite to say, but the fact that the building is sitting on the edge of the forest made timber a very obvious material to use. And it does have a warmth about it. It’s a nice aesthetic for a children’s school. The slatted timber also has the flexibility to accommodate the subtleties of the facade, such as the louvres and solar shading, the deep reveals, the soffits and the off-grid windows.

Going back to the roof playground, initially the planners were against it because they thought it would look like we were building another floor. We had a long debate about how best to deal with the balustrade, and whether it was glass or metal. I wasn’t very keen on glass, I have to say, but was persuaded. And I think, actually, the planners were right. We set the balustrade back and put the planting on the outside, which created this soft edge to the building. You can look south towards the city and you can look into the forest. It’s a very exciting space to be in.


The Accoya rainscreen provides a consistent harmonising envelope around the whole building, even where facades are mostly blank.

Claire Barton I admire the restraint used in your elevations. The detailing of the timber has some quite playful qualities. But the form is quite simple. I think that proportion really helps it against the main building. If it was too frilly it wouldn’t really stand up to its context. So it has got a strength, but it’s a soft strength.

Charles Thomson The planners initially said: “We want the new building to be different to the lower floors.” And we wanted the opposite. We just wanted something that wrapped the whole building. In the past, buildings have really just been plonked down with very little thought given to the spaces or relationship between them. So the campus is a bit of a warren of roots and happenstance spaces, which then open out on to the cricket field and the green beyond, which is actually very nice.

Claire Barton Whenever we go into a school, and they say “We just need a new science block” or “We just need this”, your immediate thought is “Well, we want to give the overall school as much added value as possible”, and that’s really, really critical, isn’t it? Here, that opportunity was quite limited but that little link that ties it into the existing building is beautiful and it makes the whole thing so accessible. Little things like that are really important, just to offer that added value to the existing setting, and give everyone a piece of the pie, not just the prep school. That’s something that we’re always trying to do. It’s good to see that you’ve done that there.

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Forest School
Studio 54 Architecture
Structural engineer
Services engineer
Cost consultant
Building Regulations
Geoff Wilkinson/The Building Inspector
Acoustic consultant
KP Acoustic
Kate Blee
Rooftop perimeter landscape
Honor Bates
Main Contractor
Claremont Refurbishment Ltd

Wall Steel UK
M D Enertech
MIB Electrical Engineers
Platform lift
Built in storage units
Boyco (UK)
Glass balustrades
Regal Balustrades
Sliding folding door
Style Door Systems
External planters
Mitre and Mondays
Complete Blinds Service
Windows and external doors
Idealcombi A/S
Roof insulation/membrane and playground roof tiles
Carlisle Construction Materials
Accoya external timber cladding
Arnold Laver & Co
Cladding fire protection
PTG Treatments
Internal doors
Dorplan Contracts
Engineered timber floors
Ted Todd Fine Wood Floors
Sheet floors
Marmoleum by Forbo Flooring UK
Heckmondwike FB
Sprung floor
Junkers UK
Fresh air ventilation
Linea Lighting
299 Lighting (Rio)
Teti by Artemide GB
Toilet cubicles
TBS Amwell
Armitage Shanks and Ideal Standard UK