Scotlarch and Siberian Larch – a comparison guide

Architectural Liaison Technician

Russwood have a rich history of supplying Scottish-grown European Larch (Scotlarch®) and Siberian Larch (SILA Select®) cladding for award winning projects of varying scale, type and design. While it is true that both belong to the same Larix genus, European Larch and Siberian Larch are two different timber species with their distinct aesthetic and unique physical properties, which are important to consider when specifying.

All Russwood timbers are FSC® or PEFC-certified and come from well-managed forests only. Most of our Scotlarch® originates within 100 miles of our Highland sawmill making it a sustainable timber with low embodied energy. Our Siberian Larch is sourced from sustainable forestry in Siberia and is imported to the UK in a rough sawn state. Depending on which mill it came from the boards will have a variety of surface finishes and markings which Russwood skim off to produce a clean, unblemished fine-sawn finish.

To achieve the Scotlarch® grade of Scottish-grown European Larch, Russwood use heartwood only to ensure there’s no sapwood (non-durable part of timber) on exposed board faces. Scotlarch® comes in a warm mix of colours ranging from pale orange to reddish brown, and has frequent knots which demonstrate its natural origins and give it a characterful, somewhat rugged appearance. The timber perfectly suits designs aiming for a more rustic and traditional aesthetic in ‘board on board’ and other simple arrangements using larger standard sections of 150×22 and 73x22mm.

In contrast, Russwood SILA Select® grade of Siberian Larch offers a contemporary timber look. The species combines dimensional stability and durability with a clean, relatively knot-free expression. The colour of SILA Select® varies from light reddish brown to golden brown. During Russwood’s stringent grading process, the highest quality of Siberian larch timber available is taken a step further to ensure that each board is practically centre free, doesn’t contain sapwood on its main exposed face and has a limited number of only tight live knots. Enhanced performance of dimensional stability can be achieved by using narrower widths, for example 120mm, and 95mm. SILA Select® is suitable for profiling into a wide selection of overlapping, interlocking and open rainscreen profiles. For projects requiring a higher grade of Larch cladding, a limited quantity of SILA A+ grade can be supplied.

The UK’s climate conditions result in a fast-grown Scotlarch® timber which, in certain conditions, can move and develop surface checks (small splits). Larch also contains resin which can become more noticeable in the summer months. For these reasons painting Scotlarch® is not recommended as this can require frequent maintenance. SILA Select® is a more suitable material for coating than Scotlarch®. Darker colours can increase heat gain which draws resin to the surface of boards. When resin dries, it becomes light in colour and therefore more visible on dark surfaces. A much better substrate for dark coatings, which can be affected by heat gain, is Russwood’s Thermopine timber which contains no resin.

Both Scotlarch® and SILA Select® weather to a muted shade of silver/grey when exposed to outdoor conditions – a desirable aesthetic in many cladding projects. For design situations where uneven weathering may be causing concerns, Scotlarch® and SILA Select® can be coated in SiOO:X to provide an accelerated uniform weathered appearance with low maintenance requirement – a perfect solution for buildings which are difficult to access for maintenance, and for our customers who wish to have a beautiful cladding application.

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