About Co2 Larch ®
Siberian Larch is a straight grained timber with few knots and good durability/resistance to insects making it an ideal timber for cladding, fencing, decking and flooring. We only sell
Unsorted I – 3 A/B Grade***, which is the highest grade available in regards to quality and look. It is known as unsorted and consists of the highest three appearance qualities i.e – I-2 & 3.
A Grade
Co2 Larch® A Grade - Has small tight knots and is suitable for all our products.
Additional Information
Siberian Larch can be left untreated or treated with a suitable exterior product.
(Please see Our Accessories page)
Have a durability class 3 rating* (BS EN 350-2 classes), and is incredibly hard, Janka Scale** of Hardness of 1,100 lbf (4,900 N). It is the only conifer that is classed within the hardwood group of timbers, and is compatible in hardness to oak (Janka Scale** English Oak 1,120 lbf (4,980 N)).
*Durability
When selecting your timber type for your project it is worth taking in to consideration BS EN 350 timber durability class.
Durability is the ability of a species to resist decay either naturally or through preservatives. The Class is based on the ability of the heartwood (inner part of the tree) to resist fungal decay. The sapwood (the living outermost portion of the tree)is considered not durable and should not be used for external projects without preservative.
BS EN 350 has 5 classes of durability they are:-
- Class 1 Very durable (Such as Tropical Opepe and Iroko)
- Class 2 Durable (such as Co2 Cedar Cedar) Co2 Grandis
- Class 3 Moderately durable (Such as European larch, Cedar (UK), Co2 Larch ® Siberian Larch, North American Douglas Fir)
- Class 4 Slightly durable (Such as Home Grown (UK) Grow Douglas Fir)
- Class 5 Not durable (Such as Sitka Spruce)
Class 1 to 3 can be left as untreated timber, a natural ageing process will accrue e.g. Larch will turn a grey colour. Class 4 and 5 will need to be treated with preservatives.
For further information see www.greenspec.co.uk/building-design/cladding-durability-quality
**Janka Scale Explained
The Janka Scale is very useful in directly determining how well a wood will withstand dents and dings. Furthermore it can be useful as an quick indication of how difficult a specific timber is to nail screw, sand or saw.
The number listed is the amount of pounds-force (lbf) or newtons (N) required to embed a 11.28 mm diameter steel ball into the wood to 50% of the ball’s diameter.
***Quality Grades According to BS 1186-3
BS 1186-3 has 3 grades applicable to external timber cladding, mostly concerned about the size and frequency of knots::-
- Class 1 Is suitable for ‘high status’ buildings. Using cladding boards of 100 – 150mm width, sound knots are limited to 22.5mm. Most hardwoods are available to this quality, and our Co2larch® and Co2Larch A+ Grade (Knot Free).
- Class 2 Is the most common classification for unfinished timber cladding. Sound knots are limited to 35mm.
- Class 3 Is generally the traditional class for painted cladding. Knots are restricted to 50mm or no more than the 35% of the board width.
For further information see www.greenspec.co.uk/building-design/cladding-durability-quality
