PRESERVATION OF WOOD

Press, Volume XCVII, Issue 28481, 10 January 1958, Page 7

PRESERVATION OF WOOD

Prevention Of Dry

Rot And Mould

Dry rots and moulds are of some importance to anyone using timber or timber products, says the house magazine of Whakatane Board Mills. Decay is caused by rots, or more properly, fungi, of which there are 57 varieties. There are those which exist in living trees and cause rot in the sapwood or the heartwood, or both. Most of them get in through wounds in the bark of the stem or roots and may live in the tree for many years. This causes very serious degrading in the timber, if not dried quickly enough, or in logs if they are left lying about in the bush too long.

Some fungi do little harm to the strength of the timber, but they do spoil the appearance. Others cause decay and in time so seriously weaken the pieces of wood that they ultimately collapse. Wind-Blown Spores

The spores (equivalent to seed in larger plants), as fine dust, are blown about by the wind and fail everywhere. Most of them fail to germinate; but now and then one lands on a suitable place and starts to grow. It will be only one in many millions, but a mature fungus produces many millions of spores.

The one that lands in the right place starts to grow and puts out roots or the equivalent of roots, and these, which are like very fine threads, penetrate into the cells of the timber and as they do. so they exude acids and enzemes (ferments), which dissolve the wood substance.

Water and carbon dioxide gas are generated and of course the wood gets weaker and weaker until it may turn into a soft and slimy substance, or brown cubes, or it may become honeycombed as with the kaikaka in totara or any other number of forms. Timber can be made more durable by treating it with preservatives of various sorts, but a better way is to keep it so dry that the wood destroying fung|, cannot operate. Established building practices which aim at making watertight joints and allow good ventilation should be followed. The paint coat should oe maintained in such a state that it will exclude the rain and immediate attention given to leaking pipes and spoutings. Under a house there Should be adequate ventilation and in the ceiling too. For as long as there is plenty of air circulation, house timber in this country .will stay naturally below the critical moisture level at which the decay fungi can operate.