Mountain Larch – "Richter wood quality criteria" for larch wood
Exclusive use of mountain larch (larix decidua) from the Alps. It grows 1000 - 1800 m above sea level and comes from sustainable forestries. Since October 2001 our wood supplier has been certified according to EN 45011 PEFC. This certificate confirms that the sawn and round timbers produced and traded come from sustainable forestry.
According to an official assessment, larch (larix decidua) is a moderately rot-resistant type of wood - considerably less durable than oak or, particularly, robinia.
However, there are different kinds of larch. The larch (larix decidua) which we use for our production grows in the mountains at a height of more than 1000 m above sea level. Therefore, it has considerably better physical properties (and thus should actually be called larix decidua montania). The advantages of this mountain-grown larch are considerable:
- fewer resin galls
- fewer splinters
- closer year rings, therefore higher stability
and especially enhanced durability.
Our larches are felled in winter so that the cut wood can dry before fertile fungus spores appear which can lead to early decomposition.
During the natural ageing process of the tree, core materials are deposited in the wood. This corning is responsible for the rot-resistance of the mountain larch. Our employees recognise good corning from the red colour of the wood.
We have tightened the Richter wood quality criteria. Timbers of mountain larch are delivered practically without sapwood.
Wood with close year rings is more resistant to rot. Wood intended for inserting into the ground and for horizontal beams has particularly close rings. Our poles have at least 8 year rings in the outer 2 centimetres.
We ensure that poles inserted into the ground and horizontal beams, have centred rings so that close ring wood lies near the outer edge. We do not permit a pith eccentricity of more than 3 centimetres.
Occasionally even a standing tree is attacked by fungus. Such wood only provides limited durability, which is why we ensure we discard it.
Wood-destroying fungi require high levels of moisture in the wood. We increase the lifespan of our wood through natural open-air drying. Advanced drying in the poles is demonstrated by the appearance of splits. Our sawn timber is already dried to 20 % of original wood moisture before it is used for construction.
Since 1989 we have manufactured much of our wooden play equipment from unimpregnated mountain larch. Our play equipment made of unimpregnated poles of mountain larch stands as a rule on steel feet. For short vertical pole lengths we are increasingly doing without steel feet construction. The end-grained timber surfaces are given an angle cut covered with paraffin wax to avoid absorption of water.