Siberian Larch, or Larch weatherboards and claddings are increasingly finding their way into the New Zealand construction market.
Commonly used as a vertical shiplap cladding, or rusticated weatherboard, Larch typically has a knotty appearance in cream / brown colour.
Some of this demand has been created by the increased prices on the more popular Western Red Cedar.
While New Zealand has a small amount of locally planted Larch, the bulk of Larch used on the market today is Larix Siberica imported from Russia.
Siberian Larch is a fine timber with tight growth rings, predominantly due to the slow growth occurring in the extreme cold. Contrary to many beliefs - the tight growth rings don’t necessarily promote excellent stability.
Siberian Larch has proven to cup and warp in New Zealand conditions - see below image.
Manufacturers have moved to producing thicker external cladding boards at 30mm thick - however this does not change. While Larch has average stability in service, it is clear that Siberian Larch is naturally more durable and more dense than it’s locally grown counterparts.
Natural durability rating refers to the timber decay performance both in ground contact and above ground. Durability in New Zealand is generally measured using the Australasian natural durability classification
System - (AS 5604-2003), which classifies timbers into four durability classes:
Class I - very durable
Class 2 - durable
Class 3 - moderately durable
Class 4 - non-durable.
Larch is currently listed as Class 3 “moderately durable” under AS 5604, and it is expected Siberian Larch is at the higher end of this scale.
Larch does have a propensity to grow surface mould, so semi-transparent surface coatings should be selected with care.
Dependent on grade, Larch is typically a tight knot species with smaller, numerous tight knots. Given the smaller diameter Siberian Larch logs, Siberian Larch is rarely available in widths wider than 200mm.
For a locally grown, FSC® certified alternative to Larch weatherboards, consider Abodo’s Tundra Cladding.
Selected from Douglas fir heartwood, Tundra Cladding has similar stability to Larch, with Class 3 durability.