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Engineered timber CLT

levels of energy required for its manufacture (just 1% of that required for steel6) and inherent carbon sequestration, CLT offers a near perfect model of efficiency. To create such efficiency in factory conditions is arguably an easier task than managing the same efficiency on a UK building site, but CLT can have a positive knock-on effect beyond a building’s superstructure leading to waste reduction across a whole project.

Saving costs and resources A combined study by Waugh Thistleton Architects, Alinea Consulting and Engenuiti in 2017 ran comparative models for a seven-storey 294-unit residential building in both CLT and concrete. The results identified a significant reduction in pile quantities due to the reduced building weight afforded by CLT with a cost (and resource) saving of 12% over the substructure elements.7 An important differential between CLT and framed structural systems is that CLT provides more than just structure. Used carefully and detailed appropriately, it can also provide a highquality and robust interior finish. For architects this appeals greatly, as it provides an opportunity to add richness and character to interiors without the need for additional finishes.

Reducing plasterboard use Typically in UK projects, gypsum-based plasterboards remain the go-to interior finish for buildings, which is reflected in the levels of waste; it is estimated that plasterboard waste will account for 500,000 tonnes of construction waste by 2020.8 The Construction Resources and Waste roadmap identified 90% of plaster-based products going to landfill and this has now become a target area for improvement.8

Grange Primary School, London. Photo: Tim Crocker

Strengthening the argument for reducing plasterboard use (and therefore waste), industry-funded studies suggest that timber finishes offer a benefit to the health and well-being of building occupants.9

Case study Maccreanor Lavington recently tested some assumptions regarding CLT with real-life data after it was appointed to design two of six schools for London’s Borough of Southwark to be built by Morgan Sindall. Both Maccreanor Lavington’s design schemes were constructed from CLT, where the remaining four were a combination of concrete and steel frames. An end of project review by Morgan Sindall’s commercial department ran a comparison of the larger CLT and steel/concrete framed schemes to assess their on‐site efficiency. The study identified an impressive two‐third reduction in the use of plasterboard in the CLT scheme and a 25% reduction in site waste.10

Further research and benefits There is of course an argument that CLT buildings use more timber resources than a timber-framed alternative and are therefore inefficient. Research by Smith and Wallwork engineers suggests CLT buildings use approximately 0.30m3 of timber for every sqm of floor area versus 0.15m3 per sqm for a timberframed building.11 But as seen with the plasterboard example, there are other performance characteristics of CLT buildings that help to reduce the use of other building materials in a project – shifting the balance back in favour of solid timber. CLT structures can: • reduce requirements for external insulation (or enhance overall thermal performance if the same level of insulation is used) • eliminate the need for thermal breaks • offer high levels of air-tightness.

Charles Dickens School, London. Photo: Tim Crocker

www.trada.co.uk

These factors all play a part in reducing overall levels of construction waste. >> Timber 2019 Industry Yearbook

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Timber 2019 Industry Yearbook  

The annual publication of the Timber Research and Development Association (TRADA) includes topical and technical features on all aspects of...

Timber 2019 Industry Yearbook  

The annual publication of the Timber Research and Development Association (TRADA) includes topical and technical features on all aspects of...

Profile for trada
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