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Russwood’s Siberian Larch (SILA) is the cladding of choice for many architects, contractors and self-builders, due to the fact that it is extremely versatile - being suitable for most external timber cladding applications - has excellent durability properties and displays attractive figuring. 

Appearance

Russwood’s SILA boards come in a warm mix of colours, from light reddish brown through to golden browns. When weathered the colour changes to a muted grey tone, which is desirable in many cladding projects. 

With clearly marked annual growth rings, straight grain and relatively few knots the overall look displays attractive figuring with a contemporary look.

Important information regarding sawn-faced profiles or board on board arrangements

Siberian Larch is imported to the UK in board form. Depending on which mill it came from it will have variety of surface finishes. For example, circular sawn marks, twin arbour lines, paint marks, grease marks or compression marks from steel securing bands. To avoid an unsightly surface finish, Russwood skim the face of each board to provide a clean, unblemished fine-sawn finish. See a short video of our skimming process below. 

Grades and specification

We offer three grades; A/B, A+ and B/C, with the specifications being as stated below.

Russwood SILA A/B®

Russwood offers SILA A/B® grade which presents an ideal combination of durability with a clean, relatively knot free look and is ideal for design led projects. The specification for SILA A/B® is as follows:

Russwood SILA A/B® <=25mm

  • Graded to BS1186-3 Part 4 Class 1; each board is practically centre free, one face will be sap free, tight live knots have a maximum 25mm diameter and a maximum of two knots per metre on average over the total length of the boards
  • As Siberian Larch is imported to the UK in board form, to avoid unsightly surface finishes such as circular-saw marks, paint/grease marks and compression marks from steel securing bands, Russwood skim the correct face of each board to provide a clean, unblemished fine-sawn finish
  • Kiln-dried to moisture content of approximately 16-18% (+/- 2%)
  • End checks permitted not longer than 1.5 times width of board
  • Lengths up to 6.0m
  • We select from the best available grades in Europe and guarantee that your order will not contain any commonly available, lower quality grades such as IV’s or sawfalling
  • FSC®-certified product sourced from sustainable forests

Russwood SILA A/B® >=25mm 

  • Graded to BS1186-3 Part 4 Class 2; each board is practically centre free, one face will be sap free, tight live knots have a maximum 35mm diameter and a maximum of two knots per metre on average over the total length of the boards
  • Kiln-dried to moisture content of approximately 16-18% (+/- 2%)
  • End checks permitted not longer than 1.5 times width of board
  • Lengths up to 6.0m
  • We select from the best available grades in Europe and guarantee that your order will not contain any commonly available, lower quality grades such as IV’s or sawfalling
  • FSC®-certified product sourced from sustainable forests

Russwood SILA A+ <=25mm

Russwood also produces a limited quantity of A+ grade. This is virtually a clear grade timber, providing a clean, consistent, almost knot-free look combined with excellent durability. At times these boards are in limited supply. The specification for SILA A+ is as follows; 

  • Graded to BS1186-3 Part 4 Class 1; each board is practically centre pith free, one face will be sap free
  • Further hand-selection of clearest grade boards which meet stringent criteria; tight live knots with a maximum 12mm diameter and a maximum of two knots per metre on average over the total length of boards
  • As Siberian Larch is imported to the UK in board form, to avoid unsightly surface finishes such as circular-saw marks, paint / grease marks and compression marks from steel securing bands, Russwood skim the correct face of each board to provide a clean, unblemished fine-sawn finish
  • Kiln-dried to moisture content of approximately 16-18% (+/- 2%)
  • End checks permitted not longer than 1.5 times width of board
  • Lengths up to 6.0m
  • We select from the best available grades in Europe and guarantee that your order will not contain any commonly available, lower quality grades such as ΙV's or sawfalling
  • FSC® certified product sourced from sustainable forests

Russwood SILA B/C

Additionally, Russwood offers SILA B/C, a more rustic grade of Siberian Larch than our A/B and A+ grades. It gives a more knotty, less uniform look, without compromising its excellent durability properties. The specification for SILA B/C is as follows;

  • Graded to BS1186-3 Part 4 Class 2; tight live knots have a maximum 50mm diameter and the majority of boards will have at least one sap-free face
  • Kiln-dried to moisture content of approximately 16-18% (+/- 2%)
  • End checks permitted not longer than 1.5 times width of board
  • Lengths up to 6.0m
  • Some boards may feature canter/circular saw marks. We therefore recommend re-sawing when using as a board-on-board finish, to create a consistent, clean, bandsaw finish

NBS Specification

For advice on completing the NBS H21 for Siberian Larch cladding please get in touch with our project team.

Durability

For external cladding purposes, Siberian Larch is a naturally durable timber (Class 3 according to BS EN 350-2) due to a combination of factors;

  • The presence of tannins in the wood create a high resistance to decay and rot, making Siberian Larch one of the toughest and most durable softwoods
  • High density means that it is more difficult for decaying organisms to penetrate the wood

With a lifespan of 50 -100 years when correctly detailed and subject to general outdoor exposure, this is similar to Russwood’s Architect Select® Western Red Cedar. Better durability properties can only be achieved with Russwood’s modified timber product: Accoya® wood.

Stability

The tightness of the growth rings and the high proportion of late wood enables a smoother machine finish and enhanced dimensional stability.

Additionally, Russwood's SILA is kiln-dried to approximately 16-18% (+/-2%), the optimal moisture content for external cladding. This moisture level is retained until delivery to site and your cladding can then be installed immediately upon delivery.

Enhanced performance of dimensional stability can be achieved by using narrower widths, for example 120mm, and 95mm.

Density

Due to its high percentage of heartwood (75-90%) and a minimum of sapwood (we guarantee that at least one face will be sap free) SILA is an extremely dense timber, classified by BS EN 350-2 as approximately 628 Kg/m3 at a moisture content of approximately 18%. As such, it is not easily damaged and therefore is ideal for highly exposed elevations, or applications where there is the likelihood of physical damage such as knocks or scrapes (e.g. schools, shopping centres, public walkways).

Coating suitability

Optimal performance is always achieved with sawn faced finishes.

SILA can be factory coated in SiOO:X, a breakthrough water based silicone technology, to provide a genuine silver lustre. In effect, SiOO:X creates a weathered appearance at an accelerated rate. Following application, all areas, regardless of protection and exposure, take on consistent tone which provides a solution to differential weathering whilst strengthening the timber's surface and creating a water repellent layer. SiOO:X is also available in a mid-grey colour. For further information about SiOO:X click here

SILA can also be factory coated in your choice of colour from Russwood’s Teknos paint range. As with all Larch species the best coating performance is achieved by using opaque colours on a sawn surface.
SILA can also be fire-retardant treated.

Fixings

How timber is fixed is fundamental to its long term performance in relation to both appearance and durability.

We offer a range of fixings and systems designed by Austrian Timber Engineers to make cladding look better and last longer. There are a number of options when considering cladding fixings. Sihga's FassadenClip® offers secret fixing giving a modern clean finish where no fixings are visible. Also available from Russwood is Sihga's F-BohrFix® ZB screw for effective secret fixing of tongue and groove profiles or RW119 secret fix profile. For face fixings L-GoFix® A2 screws combined with KompeFix® offer a superior look and performance to alternative face fixing arrangements. 

These systems can be written into the NBS H21 specification. For more information on our recommended fixings, click here

Surface Finishes

We can produce Siberian Larch in four different surface finishes to suit your specific project requirements and vision;

  • Wire Brushing - To create this effect, wire brushes are used to pull out the softer spring wood, exposing the harder summer wood, thus accentuating the grain and creating a beautifully textured surface.
  • Skimming - To avoid an unsightly surface finish, we skim the face of each board to provide a clean, unblemished fine-sawn finish. 
  • Planed - Boards are run through our planing mill to create a smooth, dressed finish.
  • Microtex - Is a uniform, consistently fibrous surface finish. This provides enhanced coating performance as the increased surface area of the cladding face enables enhanced adhesion properties. 

Sustainability

Russwood’s SILA is FSC®-certified, meaning that it is sourced from well-managed forests.

Size

SILA grade of Siberian Larch  is available in varying lengths up to 6m. Please note that cladding is supplied as a linear meterage based on random stock lengths at time of picking order. Other sizes may be available on request. 

The standard board measurement is 150mm wide as traditionally this is the most commonly produced cladding board. However, at Russwood we also offer a range of board widths including, 125, 100mm and with additional machining 73 and 47mm. The narrower board widths offer a number of advantages including more choice in design arrangements and improved dimensional stability. As an additional benefit narrower width boards are generally graded well in excess of their specification. 

Limited stock of wider boards e.g 200mm, may be available on request.

For large-scale projects we also have the ability to finger-joint and edge-glue SILA. This process allows the customisation of lengths, which could be particularly desirable to create a design look whilst eliminating on-site waste. Seamlessly joining shorter boards together can create a cleaner, more dimensionally stable grade at where bulk long lengths are required. 

Profiles

We can advise you on the most suitable species and profile for your project. Visit our profiles section to view some of our most popular profiles, or speak to us to discuss further options.

Price

Please see our cladding comparison table for price range..

Summary

  • Clean and contemporary look
  • Suitable for most types of cladding application
  • Excellent density and durability
  • Stringent in-house grading of every board
  • Sustainable

For a printable summary of the above information, click here to download our Siberian Larch Cladding Factsheet.

 

BTE Architecture
Russwood are flexible, knowledgeable and professional. The expert advice given throughout the project was key in the project's overall success

Sean Edwards, BTE Architects