DECAY IN TIMBER AND WAYS TO PREVENT FUNGAL ATTACK ON TIMBER
The biological invasion of specific species of fungi within the timber causes decay in timber. The conditions required to prevent the growth of fungi are to avoid oxygen, moisture and nutrients, with moisture being the most important factor. The timber rotting fungi can remain inactive for years, waiting for these ideal conditions to emerge. Even though oxygen and nutrients are available, the fungus will lie idle if moisture is not present in the timber.
Table of Contents:
1. Causes of Timber Decay
Any one of a number of wood–destroying fungi may attack timber that is persistently wet and has a moisture content of over 20%. Although in a new house, the moisture content of timber may for a while be as high as 18 percent, this is soon reduced in normal circumstances to some 12–14 percent, so that in fact, a sound, dry building has nothing to fear.
Most Fungi require oxygen for its survival and growth. Timber may last a long time at the base of a lake or the sea, due to inadequate air at bottom for decay organisms to thrive. The test comes when the timber is exposed to alternating dry and wet conditions – for example as a fence post.
It may seem contradictory that ventilation is one of the essentials for preventing the development of fungal decay. Even in the most stagnant and poorly ventilated environments, there would be enough oxygen to satisfy the requirement of fungal growth. However, ventilation is used to dry and maintain dry timber in structures.
It is not necessary that all construction timber should be given a preservative treatment. In the case of most buildings, it is impossible to treat the existing timber members because of the high costs and the effectiveness of the application. The main thrust should be to create conditions that are not conducive to the growth of insects and fungi. If chemical treatment had been the norm for the timber, then there would not have been a single timber framed building in Kerala.
2. How does Fungi attack Timber?
Fungal decay starts from “spores”. They are the equivalent of plant seeds, very small and can float in the air. They are scattered by air, water, animals or man. They occur in such large numbers and when conditions are suitable for fungal germination on timber, the timber decay starts.
3. Types of Rot