Branching Out: Using UK Timber
Can the construction industry support the UK timber industry
by specifying and procuring responsibly sourced UK grown timber? Charlie Law,
Founder and Managing Director at Sustainable Construction Solutions and
Sustainability Director at TDUK explains how.
The UK Government’s Timber in Construction Roadmap sets out
a clear route to increase tree cover in England to 16.5% by 2050, but also to
make good use of this resource by encouraging more use of timber in
construction. The UK is the second largest net importer of timber in the world
– only China imports more. The latest figures from Forest Research show that,
of the 15.8million m3 of timber consumed in the UK in 2022, almost 9.7million
m3 (61%) was imported, mainly from northern Europe. However, it is estimated
that almost 80% of the construction industry’s requirements are being met by
these imports, meaning much of our UK grown resource is being used elsewhere.
To ensure we have access to enough timber to meet the growing demand for
structural timber going forward, we need to increase the supply and use of our
UK-grown resource.
Currently only around 63%-67% of the UK net annual increment
(NIA) is felled. The NIA is the net annual volume of timber available to
harvest – considering any natural losses. The timber available to harvest is
predicted to increase by around 20% by 2039, before falling back to current
levels. Government targets to increase tree planting in England, means we will
also have more timber available for use in construction over the long term.
This means at least a third more of our UK grown timber resource could be
available for construction if the demand was there. Using more locally grown
materials means we can reduce the embodied carbon from transport, which will
help decrease an asset’s embodied carbon footprint. Products such as softwood,
chipboard, OSB and MDF are all readily available from UK grown sources, unlike
UK hardwood and plywood.
Softwood
Over half of all the timber consumed in the UK is sawn
softwood, so this should be a key area of focus for timber specification. Of
the UK annual resource of just under three million m3, it is estimated that a
third is used for pallets, a third for fencing, with the final third used for
construction.
In the UK, coniferous trees like spruce grow very well, maturing
in around 40 years. This makes excellent structural timber at strength class
C16, suitable for most general construction applications like structural timber
frames, floor joists, rafters and cut roof timbers, and internal partitions.
Coniferous trees in colder climates like the Nordic countries grow more slowly,
coming to maturity in 60 years or more. This produces a higher proportion of
timber meeting the properties of strength class C24/TR26 or higher – which
makes them great for longer span floor joists or trussed rafters. On average,
the wholesale price of C16 timber is 10% less than C24.
To make the most efficient use of wood resources we need to use the whole range of wood products available, and that means fully utilising both C16 and C24 timbers for the right situations. TDUK publishes free span tables for C16 and C24 strength grades, so you can choose the right grade of timber for the right application. For example, 45mm x 220mm C16 softwood timbers could be used as floor joists spanning up to 4.19m (assuming a dead load <0.25kN/sq m and imposed load <1.5kN/sq m),whereas 45mm x 220mm C24 softwood timbers would only span a little more, at 4.66m. One UK manufacturer is also producing roof trusses from UK-grown C16 softwood rather than the C24/TR26 that is normally used. By specifying the right strength grade for the right application – and not over specifying – we can ensure we make the most efficient use of the finite sustainable softwood timber resource available to us.
Hardwood
About 5% of all timber consumed in the UK is sawn hardwood,
and only 3% of this comes from UK woodlands. A Grown in Britain (GiB) WoodStock
Report found that more oak was used in the UK than all other hardwood species
combined, making up a whopping 57% of all specifications. Utilising only one
species of hardwood to this extent is not sustainable, and the report
recommends an increased focus on UK grown hardwood resources and alternative
species specified wherever possible.
Sheet materials
Most chipboard, OSB and MDF used in the UK is already
manufactured in the UK, and these utilise much of the by-products from sawn
softwood and hardwood processing that would otherwise go to waste. Chipboard is
used in everything from tongue and groove flooring to kitchen cabinets and
incorporates both chips from the sawing of timber as well as post-consumer
waste wood. OSB on the other hand uses the smaller diameter thinnings from
forests as well as the tops of sawlog trees.
Plywood isn’t manufactured in the UK, so we should consider
specifying OSB as an alternative wherever possible, e.g. for roof sheeting or
additional support within partition walls. There are now many different
specifications of OSB that can be used for numerous applications. Not only does
this mean we use more of our homegrown resource, but data published recently by
TDUK, suggests UK manufactured OSB has less than a fifth of the embodied carbon
of imported hardwood plywood.
Responsible sourcing
It is vital to ensure the timber we purchase has come from
responsibly managed woodlands in the UK – it is important to understand what to
ask for. This includes material recognised by the UK Government’s Central Point
of Expertise on Timber (CPET) and its UK Timber Procurement Policy (UKTPP).
Compliance is demonstrated via Category A Evidence – independent, third-party
forest certification schemes, such as Forest Stewardship Council (FSC) and
Programme for the Endorsement of Forest Certification (PEFC) plus Category B Evidence
– all other forms of evidence – with Grown in Britain (GiB) certification or
Forest Law Enforcement Governance and Trade (FLEGT) licenced timber examples.
UK grown timber can be used for many of the applications for
which we currently use imported timber. By making informed choices, specifiers
and purchasers can ensure that more of the timber used on their projects is
locally sourced, which helps the UK economy, and can lead to lower embodied
carbon projects.
