Need help? Ask an expert

01540 673 648

My lightbox (0)
Add products to lightbox to review choices & request samples

Vertical Grain/Semi Vertical Grain Siberian Larch (SILA) decking is a naturally durable and aesthetically pleasing product, particularly popular for projects with a requirement for both timber cladding and decking, as using SILA can create a consistent look throughout the exterior of the project.


Russwood’s Vertical Grain (VG) / Semi VG SILA decking boards come in a warm mix of colours, from light reddish brown through to golden browns.  The grain of the wood is exceptionally straight and the annual rings are close fitting. This product meets customer demand for natural looking decks. When weathered the colour changes to an even shade of grey.  If used in a project alongside SILA cladding, the weathering of both products will ensure consistency of the overall look over time. Growth rings mainly run in straight lines on the surface – which means minimum risk of surface checking and minimum risk of splinters forming as a result of delamination between the growth rings.

Specification for Mixed Grade VG/Semi VG Siberian Larch Russwood SILA Decking

  • This is only supplied as a mixed grade comprising A+ grade, A/B grade and C grade. Breakout being approx. A+ = 70%, A/B = 23%, C = 7% 
  • A+ grade maximum pin knot size 12mm diameter (in effect virtually clear grade)
  • A/B grade maximum through knot size 25mm diameter
  • grade maximum through knot size 65mm diameter. In all grades there is no restriction of size or number of splice knots (which means judicious cross-cutting may be required)
  • PAR, (Planed all round) 4 chamfered edges
  • Lengths of 3.0m – 5.1m supplied in running meters
  • FSC®-certified product sourced from sustainable forests
  • Each board is pith free
  • Sapwood may occur on both faces on max 3% of volume, no more than 20% of board width and 30% of board length. No limitations on splice knots, no limitation on resin pockets.
  • Kiln-dried to moisture content of 16-18% (±2%)
  • Chipped out knots permitted up to a maximum of 30mm diameter
  • End checks permitted not longer than 1.5 times width of board

Vertical Grain: 

  • Heartwood – separated board with the annual rings positioned at an angle of 90° – 60°
  • Average gradient of annual rings 75°

Semi Vertical Grain:

  • Heartwood – separated board with the annual rings positioned at the angle of 60° – 30°
  • Average gradient of annual rings 45°


The way a decking board is fixed and detailed can have a major effect on its lifespan. We have teamed up with Austrian fixings specialists, Sihga, to provide a system that makes decking look better and last longer. We can write these systems into the NBS Q55 specification. The VG Sila can be secret fixed with DielenFix® for decking and FassadenClip® for cladding. DielenFix® provides an ultra clean look with face free of fixings and enhanced durability due to enhanced all four side ventilation.  For more information, click here.

Slip-resistant finish

GripDeck® is a highly effective slip-resistant insert which is applied in-house to our SILA decking. The specially bonded aggregate inserts provide an attractive and long-lasting solution to slippery decking, being rated as “extremely low potential for slip” (BS7976:2002 Part-1 3 using the Stanley Pendulum Test). GripDeck® is particularly desirable for bridges, stairs, ramps, forest walkways and commercial environments such as cafes, pub gardens, shopping centres and parks.

GripDeck® can be applied with two strips per decking board and will provide excellent slip resistance in both wet and dry conditions.


One of the primary benefits of SILA as a decking material is that it is one of the toughest and most durable softwoods; unlike most commonly available decking timbers, it is naturally durable, being rated as Class 3 according to BS EN 350-2. 

This means that it does not require any chemical treatment and in comparison to pressure treated decking, has enviable environmental credentials.

This natural durability is the result of resin and extracts in the wood, combined with a high density, which reduces the woods vulnerability to rot, decay and insect damage.  This is of key importance when considering a decking material, as a hardwearing timber is required in order to ensure the long-term safety of the deck, regardless of its environment and level of footfall.

For enhanced durability and improved stability use DielenFix® for a secret fix solution and for a face fix option use KompeFix® with L-Go Fix® screws.

The way a deck is fixed and detailed can have a major effect on its lifespan. Our systems designed by Austrian Timber Engineers will make decking and cladding look better and last longer.


The VG/Semi VG is considerably more dimensionally stable than standard flat sawn offerings. For example, flat sawn boards can move up to 50% more than VG boards. 

Enhanced dimensional stability – this reduced propensity to move means minimal shrinkage and expansion.


SILA is a dense timber, classified by BS EN 350-2 as approximately 628 Kg/m3 at a moisture content of 18%.  As such, it is not easily damaged and therefore is ideal for high traffic areas such as bridges, hotels, retail outlets and other commercial properties.

Treatment suitability

Due to the natural durability and beauty of SILA decking, it is generally left untreated to weather to a beautifully consistent shade of silver/grey. SILA is suitable for coating in SiOO:X, a breakthrough 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 a consistent tone which provides a solution to differential weathering. For further information about Sioo click here.


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


The standard Vertical Grain/Semi Vertical Grain SILA decking profile is a 27 x 92mm square dressed with bevelled edges.


SILA decking is supplied in running meters various lengths from 3.0 – 5.1m. Please note that decking is supplied as a linear meterage based on random stock lengths at time of picking order. Other sizes may be available on request.


SILA is one of our mid-range decking products, with prices starting at £40.71mfor the standard profile.


  • Produce a very special look of naturally durable decking, especially when combined with DielenFix® fixings
  • Ideal for seamlessly blending cladding & decking to weather naturally or with SiOO:X for an accelerated weathered effect and water repellence benefits
  • Particularly suited to high traffic areas
  • Natural durability; no chemical treatment required