Northstowe new town is taking shape a handful of miles from Cambridge and an integral part of its phase two development is a complex of primary, secondary, special educational needs (SEN) and community space (sports centre, theatre and café) with the all-embracing name, Northstowe Learning Community.
The 15,000m2 project features approximately 3,100m3 of cross-laminated timber (CLT), storing an impressive 3,000 tons of CO2 and it’s these statistics that help to explain why the campus is being hailed as an exemplar of sustainable construction. The fact that it is also an inspiring and healthy space for students is the icing on the cake.
The project, which won the 2020 Structural Timber Award for Education Project of the Year, was the central point for discussion in a webinar hosted by The B1M (the world’s largest and most subscribed-to video channel for construction) in conjunction with Stora Enso, which supplied the CLT for Northstowe. The wider focus of the webinar was “Why it’s time to build more wooden schools”.
Participants included Fred Mills, co-founder of The B1M, along with key members of the project team: Rory Doak, business development manager at Stora Enso; Dayo Shittu-Balogun, associate at CLT design specialist Eurban; Will Hendry, senior design manager at Kier; James Mills, architect at Frank Shaw Associates; and Andy Daly, executive principal at the Cambridge Meridian Academies Trust (CMAT). The event was attended by architects, engineers, designers and developers.
One of the early benefits of building with CLT at Northstowe was the speed, with work starting on site in January 2019, completion around July and handover of the first phase in September of the same year.
The speed of build really lent itself to the phased construction and handover that was necessary for the school, said Will Hendry. “It gave us a break line so we could carry on constructing at the same time as the students were actually receiving their education.”
All the structural requirements of the project are CLT, much, though not all of it, on full view and another benefit of this construction method is what amounts to future-proofing. For example, the sports centre currently features four courts but as the school and the town grow, the CLT panels can be lifted out and moved back to make room for a further four.
A further example of CLT’s flexibility during the construction phase was highlighted by both James Mills and Andy Daly.
“One of the important things for us was the ability to look into rooms as you walk past them and James was able to design really large vision panels into the classrooms,” said Mr Daly. “The flexibility of working with CLT made this easier than with other materials.”
“Those windows were literally just a cut in the wall,” added Mr Mills. “When it comes to designing, CLT – or any timber – is quite flexible.”
Another advantage, said Rory Doak, was the reduced noise on site because everything comes in as pre-cut and pre-manufactured panels on a just-in-time basis. “One of the biggest benefits for these sites is the reduced transport requirements,” he said. “Everything arrives on site when it’s needed, reducing deliveries by about 70%. We work pretty hard with the design teams to make sure we only send materials as and when they need it.”
“A big part of being able to have that kind of certainty on the programme was the ability to incorporate digital 4D BIM to the whole project,” added Ms Shittu-Balogun. “This allowed us to sequence things with a degree of exactness to such an extent that everything was just-in-time – just-in-time delivery and just-in-time for handover. That upfront collaboration through the whole design process, so we knew what was coming when, meant that site logistics were matched to the delivery programme. The 4D planning BIM element was integral to the whole process.”
Speaking after the event, Mr Doak said that working with tried and tested partners who were skilled in timber construction generally and CLT in particular had been fundamental to the smooth running of the Northstowe project. And, in fact, it’s key to all projects involving CLT.
“One of the big parts of my role is making sure I am able to connect project teams with the right people coming in,” he said. “Companies like Eurban, who we have been working with for 10-15 years.”
And, of course, as CLT construction grows, the body of professionals with the requisite expertise also increases.
“I get emails every day from people looking to get into this kind of construction and for us, as part of the supply chain, it is important to make it accessible with open knowledge sharing.”
That’s why Stora Enso has developed Building Concepts, an online tool that links architectural guidelines to building systems, allowing the specifier to better understand how to build with wood and find options feasible for wood construction.
Building Concepts focuses in on residential multi-storey, office buildings and schools and also features a reference library and information on life cycle assessments.
“If you are building a school or an office we have got a building concept to help take you on that journey,” said Mr Doak. “And we have a global partner network, so if you want to get in touch with someone who has done this before, we can help with that, too.
“The reference library shows buildings that have been delivered and the project teams that put them together and I think that sort of transparency in a central place is very engaging,” he added.
As for building schools with timber, Mr Doak said we’re living in a period that is the “sweet spot”.
“We [Stora Enso] have been delivering them for over a decade and we know how to do them well. There isn’t a huge premium to pay on them and sustainability is so high on everyone’s agenda that it makes sense to build schools with timber. And right now we have a huge range of competent installers, contractors and consultants.”
Local Authorities and schools’ trusts are also becoming more enlightened as the number of timber schools grows and sets a precedent and the conversations around potentially thorny issues such as fire risk are “short ones”.
“Our CLT has been tested in many ways,” said Mr Doak, when speaking at the webinar. “A lot of systems that we have used have been tested across Europe and we’re still working to the same standards as everything else [other building materials]. It’s about using that real data to inform our decision makers going forward.
“We are doing all this cross industry collaboration, which is so key as timber buildings get more complicated. For Northstowe we really relied on our previous testing of the product to prove it worked.
“Again, it comes down to experience. We know the product is safe and we have competent partners, such as Eurban, who know how to specify it and use it in the right way.”
“It’s about applying a risk management and mitigation strategy early in the process, with the right specialist knowledge in the team,” added Ms Shittu-Balogun. “Every building material has its risks related to fire but really it is about the design and engineering of the structure – first of all to stand up but also to keep people safe.”
Maintenance in a busy secondary school was another cause for some nervousness from CMAT and this was countered by reducing the level of exposed timber in the high traffic areas, while allowing it to shine in others. In the SEN building, for example, it was seen that there was a real biophilic benefit to using timber visibly inside the space.
Mr Doak notes the fact that Frank Shaw Associates has designed so many timber schools that it is almost the default material now and that Kier Construction is adamant that CLT was chosen to meet the environmental credentials for reductions in noise, dust, construction deliveries and site waste.
“They aren’t looking at it from a timber purist point of view,” he said. “They are looking at the whole thing holistically and what actually fits this project – and for them it was CLT.
“It was super interesting to have a timber webinar where sustainability was only brought up at the end,” he added.
“There were so many other benefits to building with timber that we were able to discuss and I think that shows the maturity of the product.”
