We all know that timber is a sustainable, biodegradable material. And we’ve all heard of things being made from reclaimed wood. But can we go further still?
Could timber from old buildings have a second life – transformed into a structural timber product and reused?
Simple Works are London-based structural engineers (and members of TDUK). As part of a team that included ReLondon and Grimshaw Architects, they carried out hands-on research into the reuse of timber. More specifically, reclaiming it and turning it into viable glulam beams…
A cross-disciplinary team on an upcycling mission
“Our name was put forward by a mutual contact to Grimshaw, who were part of the team,” explains Phil Isaac, Director and Co-Founder of Simple Works.
The research was being coordinated by ReLondon: it was one of nine ‘demonstrator’ projects in the CIRCuIT (Circular Construction in Regenerative Cities) programme, itself funded by the EU Horizon 2020 programme.
“We were very keen for there to be an upcycling focus,” Phil continues. “We thought that glulam beams would be interesting. In some ways, upcycling timber into glulam would be like a stepping stone before CLT. You need fewer elements for glulam – we thought it would be achievable.” The aim thus became to demonstrate that timber can be reclaimed from demolition sites and reused structurally in gluelaminated timber elements.
They contacted Buckland Timber, the UK’s only manufacturer of glue laminated timber. Buckland agreed to take part despite the fact that, as Phil puts it, “manufacturing six glulam beams from dodgy timber probably wouldn’t have been high on their list of priorities!” They also contacted a few demolition contractors to try to find the timber itself.
But where to find the timber? Bingo!
“Sourcing the timber was a challenge in terms of time,” Phil explains. “Understandably, contractors don’t want to keep material lying around – there’s nowhere to store it.” In the end, Keltbray were able to supply the material. The timber was taken from a former bingo hall in London’s Elephant and Castle area, where it had been a raised access floor.
The team characterised the timber, assessing damage sustained during its life and removal that might impact its structural properties. They conducted longitudinal acoustic resonance tests to provide an estimate of the elastic modulus.
Nailing the problem
“Sorting the timber and removing nails and metal shrapnel takes a long time,” Phil admits. “If this were to become commercially viable, that would need to be mechanized.”
They had to go over the timber a few times. Most of the metal was visibly sticking out – screws and nails – and easily removed with claw, hammer or drill. Next they went over it with metal detectors for any embedded shrapnel. They thought they’d got everything. Then they sent it off to Buckland Timber. “The first step in their process is to run it through their planes. They were still finding things.”
A real test of their mettle
Buckland’s plane blades hit a couple of bits of metal shrapnel. This apparently nearly derailed the whole project. While it’s hardly ideal for plane blades to be striking metal objects, they can always be sharpened. However, the finger jointing machine was another matter – bits of metal could break the whole machine. And finger jointing machines don’t come cheap.
Fortunately, the project could still go ahead. Buckland carried out their own additional assessment before creating six glue laminated beams, which were then mechanically tested at Napier University, Edinburgh. Preliminary testing of the beams show modulus of elasticity in line with virgin timber glulam products.
Could upcycled glulam enter the mainstream?
“We’ve proved that it’s 100 percent possible,” Phil confirms. “But there are other considerations to resolve – such as insurance, warranties or liabilities. If you make a glulam beam from secondary timber do you give it the same strength classification as a new glulam beam?”
“From a technical perspective, the answer to the question ‘can you make glulam beams from reclaimed timber?’ is a big ‘yes!’”
As Phil reminds us, timber is the only widely used construction material that sequesters carbon. So we need to keep it in the supply chain. He points to all the UK’s Victorian houses whose timber joist floors have been creakily storing carbon for 150 years. If those floors end up burned then all that carbon is released.
Are we heading for an upcycled timber future?
“There needs to be much stronger incentives to upcycle timber – at policy level. There’s no reason why it couldn’t be commercialized. But given there is only one glulam manufacturer in the UK – Buckland – this is clearly a challenge.”
The next step, of course, would be to use the upcycled glulam beams on an actual building. Phil and his colleagues are itching for the opportunity.
This article is from issue 03 of Designing Timber. Read more articles from the magazine here.