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A locally sourced product - Scotlarch® Treated decking provides a sustainable, moderately durable and cost-effective solution, for commercial and domestic projects.

We supply Scottish Larch (Scotlarch®) decking in a pressure treated form so that the end result will be a low maintenance, locally sourced, natural looking deck - at a competitive price.

When should I use Scotlarch® Treated decking?

Scottish larch is classified by BS-EN 350-2 as durability Class 3-4 (slightly/moderately durable). Under EN 460 where the timber is above ground, not covered and experiences prolonged periods of wetting, we would recommend Scotlarch® Treated decking as the preferred solution. 

In applications where timber will be exposed to heat and long periods of sunlight, some naturally occurring resin exudation could be expected. In such situations we would recommend using Russwood's Thermopine Decking product.


Scotlarch® Treated decking is supplied in a uniform shade of green because, as part of the impregnation process, treatment is applied to all boards.

The product contains frequent knots, which demonstrates its natural origins and gives it a characterful look. The boards will weather to a muted shade of grey which can provide a uniform look between cladding and decking. 

Grades and specification

At Russwood we sort and re-grade every Scotlarch® board that we produce, in order to ensure that our in-house grading criteria are met. The Scotlarch® Treated decking is a selected grade, which meets the following criteria:

Specification for Scotlarch® Treated decking

  • Graded to BS1186-3 Part 4 Class 2/3; boards contain tight live knots with a maximum diameter of 50mm
  • Some resin pockets may be present
  • Kiln-dried to moisture content of 16-18% (+/- 2%)
  • Lengths up to 4.8m
  • FSC-certified product sourced from sustainable forests in Scotland
  • Preservative impregnated to green colour (in accordance with BS8417)


Scotlarch® is a moderately durable timber and is classified by BS EN 350-2 as Class 3-4 (moderately/slightly durable).

It is expected that Scotlarch® Treated decks will have a lifespan of more than 20 years (according to the Timber Decking Association). 


Due to its high percentage of heartwood and minimum of sapwood, this timber is moderately dense, classified by BS EN 350-2 as approximately 556 kg/m3 at a moisture content of 18%. As such, it is not easily marked or damaged and therefore is ideal for high traffic areas such as public walkways and other outdoor recreation areas.

Treatment suitability

Scotlarch® Treated decking is popular as it is a natural looking product with a lot of character. When left to weather and with correct detailing, it will become a consistent shade of grey. It is suitable for coating in SiOO:X, a breakthrough silicone technology, providing 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:X click here.

GripDeck® anti-slip

GripDeck® is a highly effective slip-resistant solution which can be applied in-house to our Scotlarch® Treated 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 equally suitable for domestic use, as well as for bridges, ramps, forest walkways and commercial environments such as cafes, pub gardens and parks.

GripDeck® can be applied to both our smooth and grooved profiles and two strips per decking board will provide excellent slip resistance in both wet and dry conditions.


The way a decking board is fixed and detailed can have a major effect on it’s lifespan. We have teamed up with Austrian fixings specialists, Sihga, to provide a system that makes decking look better and last longer. These systems can be written into the NBS Q55 specification. For more information, click here.


Most of our Scotlarch® originates within 100 miles of our Highland sawmill. In addition to minimising embodied energy, Russwood’s Scotlarch® is FSC®-certified meaning that it is sourced from well-managed forests.


Scotlarch® Treated decking is supplied in a standard width of 140mm, in a choice of finished thicknesses (30, 42, 55 and 68mm are the most popular, but we can supply thicker boards on request) and in varying lengths from 1.8 – 4.8m. 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.

We offer Scotlarch® Treated decking in either a smooth or grooved profile, which allows you to create the look of your choice.


Scotlarch® Treated decking is priced from £26m2 excluding VAT for either a smooth or grooved profile. 


  • Locally sourced product
  • Weathers to a grey colour
  • Can be supplied with GripDeck® anti-slip inserts
  • Sustainable
  • Suitable for SiOO:X application
7N Architects
We have used Russwood for numerous projects and they have consistently provided high quality products backed up with excellent technical service. The product (Scotlarch® GripDeck®) had the slip resistant qualities we needed for this public platform which will be used by students and staff of RSAMD and Scottish Opera

Helena Huws, 7N Architects