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Materials UK timber

• Western hemlock (Tsuga heterophylla) (TSHT): characteristic density ~380 kg/m3, characteristic strength ~18 N/mm2, mean stiffness ~8 kN/mm2 • Western red cedar (Thuja plicata) (THPL): characteristic density ~320 kg/m3, characteristic strength ~16 N/mm2, mean stiffness ~7 kN/mm2. This makes these species roughly similar to Sitka in grading terms, although the stiffness of western red cedar is likely to be too low for good grading yields. Napier is currently researching some other likely conifer species for diversification: • Serbian spruce (Picea omorika) • Pacific silver fir (or amabilis fir) (Abies amabilis) (ABAM) • Japanese incense cedar (or sugi / Japanese red cedar) (Cryptomeria japonica) (CYJP) • Grand fir (Abies grandis) (ABGR) • European silver fir (Abies alba) (ABAL). These minor species constitute only a small proportion of the home-grown timber resource but could possibly become a minor component of an existing species combination such as ‘British spruce’. So long as the aspects of the timber that are important to manufacturing and construction are similar enough, the actual botanical species or genus is of little relevance to the user, especially considering the within species variability that is already addressed by grading.

Hardwoods The available volumes of hardwood in the near future are very limited compared to the conifers, but Napier is researching sycamore (Acer pseudoplatanus) (ACPS) and birch (Betula pendula/pubescens) (BTXX), which have potential for an eight-fold and a 13-fold increase in available volume respectively by 2045.6 Old visual grading assignments exist for BS 5756 that assign European oak (Quercus petraeaand robur) (QCXE) to D24, D30 and D40, and sweet chestnut (Castanea sativa) (CTST) to D24.

Wider variety needed The changing focus of British forestry, and the increasing demands on wood fibre for energy and as a feedstock for new materials in the desired future bio-based economy, make it inevitable that the timber industry will widen its focus from the present small number of commercial species. The good news is that this does not necessarily lead to significant changes for the end user. It is, after all, the performance of the timber that matters and not the appearance of the tree it came from. n www.trada.co.uk

About the author

Daniel Ridley-Ellis Head of the Centre for Wood Science and Technology Edinburgh Napier University

Further reading WIS 2/3-67 Specifying British-grown timbers, Exova BM TRADA, 2017

References 1. Ridley-Ellis, D., Stapel, P. and Baño, V., ‘Strength grading of sawn timber in Europe: an explanation for engineers and researchers’, European Journal of Wood and Wood Products, vol 74 (3), pp291-306, 2016 (http:// researchrepository.napier.ac.uk/output/169717) 2. For a more comprehensive overview of current grading options for UK-grown timber, see Ridley-Ellis, D., ‘Strength grading of timber in the UK in 2018’, Timber 2018, Conference of the Wood Technology Society, 2018 (http:// researchrepository.napier.ac.uk/output/1248720) 3. Moore, J., ‘Wood properties and uses of Sitka spruce in Britain’, Forestry Commission Research Report, ISBN 9780-85538-825-6, 2011 (www.forestry.gov.uk/pdf/FCRP015. pdf/$FILE/FCRP015.pdf) 4. Ridley-Ellis, D., Adams, S. and Lehneke, S., ‘Some thresholds for grading British-grown spruce to optimised strength classes using longitudinal resonance’, World Conference in Timber Engineering 2018, Seoul, Republic of Korea (http://researchrepository.napier.ac.uk/ output/1291789) 5. Gil-Moreno, D., Ridley-Ellis, D. and McLean, P., ‘Timber properties of noble fir, Norway spruce, western red cedar and western hemlock grown in Great Britain’, Forestry Commission Research Report FCRN026, ISBN: 978-085538-952-9, 2016 (www.forestry.gov.uk/pdf/FCRN026. pdf/$FILE/FCRN026.pdf) 6. National Forest Inventory: 50-year forecast of hardwood availability, Forestry Commission, 2014 (www.forestry.gov. uk/forestry/beeh-a2uf3d#forecastHardwood)

Timber 2019 Industry Yearbook

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Profile for BM TRADA

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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