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Siberian larch cladding

Siberian larch cladding halflap profile

Grade B Siberian larch halflap | VHL1Siberian larch, Grade B | VHL4

Siberian larch cladding supplied by Vastern Timber is sourced from reputable sawmills processing larch logs from well managed forests in northern Europe. Where possible our larch is sourced with independent certification.

Siberian larch trees grow very slowly and consequently the larch wood is extremely dense and strong when compared to other softwoods such as spruce and cedar. The high resin content found in Siberian larch makes it one of the most durable softwoods in the world.

Siberian larch, which is a straw colour, similar to pine, should not be confused with the European larch growing in Britain, which is a dark pink colour. Unlike European larch, the knots in Siberian larch cladding are a lighter grey colour and tend to stay solid even after drying and machining. For this reason we tend to favour Siberian larch over British larch for machined cladding profiles.

Siberian larch cladding is generally available in two grades, which in the trade, are confusingly named ‘Unsorted’ and ‘Fourths’ (or sometimes ‘Sawfalling’). For ease, we describe our stocks as either Grade A or Grade B. Grade A allows for occasional small knots, although many boards will be clear of defects. Grade B allows for frequent and larger knots. We most commonly offer Grade B because it offers a very cost effective cladding option. Care should be taken when relying on the trade names as the relative quality between Russian sawmills is highly variable.

As with all larch species, the Siberian version is a relatively ‘lively’ timber and as such, it is prone to distortion and dimensional variation. Throughout the year a 145mm Siberian larch cladding board can vary by up to +/- 5mm. We therefore recommend simple cladding profiles such as halflap (VHL) and splayed (VSP) that can accommodate this movement rather than more delicate TG&V profiles.

Siberian larch cladding is a good choice for exposed elevations where knocks and scrapes are likely. Grade B is appropriate for projects where a natural or rustic appearance is desired, whereas the relatively knot free Grade A will create a more contemporary looking facade.


Technical Specification

Produced to comply with the harmonised standard for construction products regulation BSEN14915:2013 and to conform to BS8605-1:2014 External timber cladding: Method for specifying.

Trade Name Siberian larch
Base timber Siberian larch
Species Larix siberica
Process None
Origin Legal and well-managed forests in Northern Russia
Intended use External cladding
Other uses Decking, joinery, structural timbers
Appearance The wood is a golden yellow colour with a strong grain pattern, similar to pine. Depending on the grade, the boards may include some, or many, dark black knots.
Weathering As the boards weather the colour will change to a silver-grey. Larch is quite consistent and is not reactive, and as such, will weather relatively evenly. Northerly elevations may weather to a darker grey than those facing South.
Profiles Shiplap, halflap and splayed profiles. Not recommended with tongue and groove profiles (VTG) due to movement.
Dimensions 20×70, 20×95, 20x145mm
Lengths Random 1.8 – 4.5mt +
Moisture content Approx 16 – 18%
Natural durability (EN350-2) Durable Class 3
Insect attack Resistant
Desired service life:(BS8417) Occasionally wet 30 yrs
Frequently wet 15 yrs
Treatability class Resistant
Movement class Large (Of our machined cladding timbers Siberian larch moves the most. A 145mm board can vary by 5mm through the year)
Resistance to impact High
Resistance to fixing Medium
Mean density 570 – 650 kg/M3 when dry
When to fix Ideally Autumn / winter months.
Grading Grade B (Known in the trade as 4ths or Sawfalling). Too knotty to conform to any standard.

Grade A (Confusingly known in the trade as Unsorted) BS1186-3 1990 Class 2. EN942:2007. J30. CE grade A. Clean with a few sound knots up to 30mm.

Working properties Good workability. Takes fixings satisfactorily.
Extractives Siberian larch contains resin rather than oil or tannin. The resin is fixed by kilning and does not tend to bleed. The resin is not reactive.
Emission of formaldehyde (EN14915) E1 (Not significant)
Reaction to fire (EN14915) Euroclass F (Untested). D-s2, d0
Fire treatment Possible by impregnation
CE compliant Yes
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