9 minute read

Timber structures: engineered timber CLT for private residential projects

from Timber Industry Yearbook 2022

from Timber Industry Yearbook 2022, page 172

Education: architecture Studio...

CLT for private residential projects

Cross-laminated timber (CLT) is an ideal solution for one-off residential projects, offering scope for design and innovation in one structural package. Lee Murphy talks to three architects about their recent CLT projects.

Lammasfield Farm. Photo: Micah Jones

“CLT is a great solution for building above an existing structure because it is lightweight and fast, but a key consideration is airtightness at the connection between the new and existing parts of the building.”

Many smaller architectural practices working predominantly in the private residential sector may not be aware that CLT is an option when they’re designing smaller scale, one-off private dwellings, extensions or garden buildings. Yet CLT is eminently suitable for these types of residential projects, resulting in beautifully designed and crafted, low embodied carbon, energy-efficient homes.

There is also a perception that building with CLT will be costly, whereas costs tend to be upfront and will generally be recouped through the speed and ease with which a building is installed and watertight once on site.

Here, three architects who worked with G-frame Structures to deliver their first CLT residential projects give advice to other architects interested in using CLT for the first time.

Lammasfield Farm

Micah Jones is an architect based in Northern Ireland who featured on Grand Designs in 2016 when he designed and built his own multi-award-winning, low-budget family home, County Down Barn, from CLT. He is currently on site with his second CLT project, Lammasfield Farm, which is due for completion in 2022.

‘The more forward planning you do with CLT the better, as this will allow you to design to the material’s full potential. The fundamental thing is to work with an established CLT contractor like G-frame; if you’ve never worked with CLT before you’d want to engage your specialist from a really early stage, even as early as conceptual level, to make sure everything is going to work.

‘We have been able to apply a lot of what we learned from our first CLT project to Lammasfield Farm as both projects have a CLT upper floor built above an existing concrete ground floor. CLT is a great solution for building above an existing structure because it is lightweight and fast, but a key consideration is airtightness at the connection between the new and existing parts of the building. Not getting this quite right on County Down Barn enabled us to learn and improve detailing for Lammasfield Farm. We also learned the value of doing a full M&E design before getting to planning stage and having it pre-machined at the factory, which makes the installation on site a lot easier. >>

Lammasfield Farm CLT detail. Drawing: Micah Jones

‘CLT brings everything together in one product: in addition to providing the superstructure of a building, it opens opportunities for design, aesthetics and minimising carbon footprint. This is an important factor for clients in the residential sector who are becoming more aware and are interested in paying a little more to achieve a low impact home.’

The Gatehouse

Alessio Cuozzo is a founding partner of London-based Cuozzo Fleming Architects who are currently on site with their first CLT project, The Gatehouse – a four-bedroom, wheelchairaccessible dwelling that sits within a stretch of protected ancient woodland on Sydenham Hill, South London. It forms part of the overall redevelopment of Beltwood House, a Grade II listed Victorian villa.

‘CLT suited the nature of the design of The Gatehouse, which has a simple plan of two squares with steeply pitched roofs, and this provided us with a good opportunity to try CLT at a scale that we could control, in order to avoid any visual structure between the roof planes.

‘One of the reasons we decided to use CLT was its speed and ease of construction: our client chose to self-build The Gatehouse and CLT enabled us to take some weight off his shoulders as the superstructure was being manufactured off-site with windows and doors pre-cut and then installed by G-frame. ‘Using CLT has given us the experience to understand its capabilities and be more innovative and ambitious on the next project. My advice to any architects thinking about using CLT for the first time would be to give it a go on something small that you’re comfortable trying it on and not to worry about the material being too big and too complex for your project. Try making a card model and scale it up; it will take away some of the mystique and you’ll be pleasantly surprised how simple the process is – if you can make it in cardboard, you can effectively make it in CLT.’

Origami House

Matt Keeler of KSKa Architects also began his first CLT project by creating a traditional card model when he designed Origami House, a unique folded plate origami structure that provides a one-bedroom family annex in the rear garden of a listed house in a West London conservation area.

‘Planning constraints around height meant we needed to keep the build-up as thin as possible. We were replacing an existing, dilapidated garden building and wanted something with dynamic visual strength to complement the site locality next to a church hall building. CLT was absolutely the right choice for the folded plate form of the building, which, though small, demonstrates CLT’s structural properties to its limits.

‘We started by building a model out of cardboard and as soon as we connected the triangles together, we felt it take on the characteristic strength of an origami form. To achieve the roof form, which is made of triangular shapes, we had to look at dimensional shapes and capabilities of the CLT, but it was not that challenging for us to massage the designs to meet the constraints that the material has in terms of panel sizes. >>

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Origami House exterior. Photo: Agnese Sanvito

‘I did a lot of research about CLT, particularly by consulting people who had used it before. We also visited a project with G-frame and that was illuminating. One of the biggest benefits of CLT is that you’re pre-determining things and sticking to the plan, so you need to understand the speed at which it goes up and you have to make sure the contractor understands this too because they must be ready with the follow-on very quickly.

‘CLT is a beautiful material to work with and the staggering thing is the level of precision and that it can be installed with such a small workforce, but it is essential to use a CLT specialist from the early stages for planning, organisation and expertise. The CLT supply chain is very streamlined.’

Summary

The resounding message from architects who have used CLT for the first time is to give it a go on something smaller, and make sure you’re working with a reputable CLT specialist from the early design stage. n

About the author

Lee Murphy Director G-frame Structures

Further information

To find out more about these projects, visit www.g-frame.co.uk

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