Wanted: a 200m2 building in London. Budget must not exceed 400K. Must be fully demountable in ten years’ time.
Sounds like a tall order? That was the challenge that faced the team of If_Do architects and social enterprise Meanwhile Space. And then there were the site constraints to contend with…
Pitching for a problematic site
Southwark Council were putting an unused plot of land out for tender. Effectively, they were giving away the site for a ten-year period. They were even offering some £100,000 to support the winning proposal – a very generous offer.
But there were conditions, Al Scott recalls. That ten-year time limit, for one thing. The successful building would have to be removed after a decade. This immediately meant that nobody would be interested in investing all that much in the building. It was this that drove the brief for a demountable structure.
Furthermore, there were serious constraints imposed by the site’s proximity to the entrance to the Rotherhithe Tunnel and to local overground trains. This meant that there are two huge retaining walls at the edge of the site – infrastructure which Transport for London were understandably concerned about protecting.
Nevertheless, If_Do and Meanwhile Space decided to pair up to tender for the project. They carried out a feasibility study together.
The site had been lying dormant for a long time. At one point in its history, it had hosted some post-war housing, which had been demolished. All that was left of it was a concrete slab, sitting on concrete strip foundations. This was to come in very handy later…
Up until the early 1980s, there had been working dockyards in the area. The locale has seen a huge amount of change, and Southwark Council were adamant that the building should benefit the local community. Meanwhile Space is a social enterprise with considerable experience of coming up with ‘meanwhile use’ sites that are of genuine use to communities. The team won the tender.
Doing the maths and working out the finances
Their proposal was for studio spaces for startups – a next step for local businesses that might otherwise be working at their kitchen tables at home. It would be a supportive place to work with others in similar positions.
There began, what Al describes as, a “huge exercise in financial modelling” to determine the size and design of the building.
“Financial modelling basically dictated the building’s design,” he elaborates. “The design was a result of all the parameters. The demountability of the building obviously had a large bearing in terms of expense. And then there was the fact that all the units have to remain affordable for locals – throughout the ten-year term.”
The building’s design consists of ten micro units on the ground floor and two larger office spaces on the floor above. The way Al describes it, it couldn’t have been any other way.
“We looked at different options – four floors, one floor – and found it absolutely had to be two floors, with those particular numbers of units.”
Tunnels, trains and retaining walls
Costs aside, those two retaining walls that Transport for London were so concerned about were another big factor in the design.
“The trains are very close to one of them, so TfL were obviously nervous about any loading on that wall, “ Al reveals. “We had to get an asset protection agreement for the building to be there at all, which took a huge amount of time, money and effort.”
“We could only load existing foundations. This was a big limitation on the building, but having that slab from the demolished housing really helped our budget.”
Adam Smith and his colleagues at Elliott Wood conducted a load-balancing exercise to prove that the slab and foundations beneath could carry the required load.
“We had some info on what was previously there and calculated that the new building would be lighter,” Adam tells us. “We could prove to TfL we weren’t making their assets any worse than what had been there before.”
There were also other caveats, says Al. They couldn’t work within 2 metres of the retaining walls – which ruled out installing a site hut, or loading the walls even momentarily.
Putting it together to be taken apart
The original intention was for everything to be assembled as pods of timber stud walls, with ply for stability.
“We then decided that, from a demountability perspective, it would be useful to introduce some steel elements – so that things could be lifted out of place more efficiently,” Adam explains. “The steel is just framing the timber panels, which are taking all the load.”
The steels can be unbolted, allowing removal of individual timber panels or whole pod units – depending on what lifting equipment is available. They can then be re-erected as either panels or pods.
The ground floor is essentially a 3×5 grid, with each unit designed to be truckable. There is a central cruciform shape in the middle to create some public space in order to cut through to the garden at the rear. There are a couple of WCs and a small refreshment area.
The upper floor uses a SIPs system – timber with insulation in the middle – for the walls. Glulam beams are used for the long, clear span of the sloped roof. Glulam columns stand on top of the ground floor’s timber frame – it’s the ground-floor timber studs that take the loads down to the foundations. Those columns and beams are all bolted and could be reused – though are tightly packed and would require some manipulation.
“Bolted connections that are accessible is key,” Adam advises. “Where we’ve boarded panels on the upper floor there are little pockets cut out where two panels are bolted together. So you can loosen them without having to pull the whole boarding off.”
The Hythe project received some funding from ReLondon. In association with Grimshaw architects, ReLondon investigated the practicalities of tongue and groove screwed timber connections. They were interested in discovering how many times you can put them back together while maintaining structural integrity between panels. One way of maximizing this is to broaden the zone in which fixings can be made: instead of an overlap designed to take one screw once, five or six new fixings could be made within it.
Completed on-budget and with all units filled
The Hithe, as it is known, was completed in 2021. There was, apparently, huge demand for the ground-floor units. They were snapped up straightaway as they are very affordable: this community benefit was factored into the construction cost from the start. Meanwhile Space themselves decided to take on one of the upstairs larger units.
“It’s about the size of a large family home, and it’s on a difficult site,” Al points out. “It’s amazing, frankly, to have got it done for £400,000. In form, perhaps it’s not the most innovative timber building you’ve ever seen. But it’s successful in many different ways: the clients and community are very happy with it. It has been up for 2 years now. The ultimate test, of course, will be taking it down, then putting it back up elsewhere.”