Dry Rot.

Progress, 1 October 1908, Page 421

Dry Rot.

By F. T. Banies-Hewitt, F. 5.1., in Illustrated Carpenter and Builder.

Timber in balk and timber in log are both liable to dry rot, a fungus growth whichattacks the timber under suitable conditions. Sap wood is more liable to attack, but even the best timber may fall under its ravages if it is in a damp and confined situation. Balk timber not properly ventilated in the timber yard or logs left lying in the forest are attacked by dry rot, especially the sap-wood. Here lies one of the dangers, for such balks or logs are frequently converted and much timber is

delivered to various jobs already infected. Timber which is quite sound when going through the sawmill may contract dry rot during its voyage to this country, either from the ship or through being shipped wet and being subject to damp, warm, and stagnant air during the voyage. The worst specimens in a cargo may be covered by the fungus growth, which is white or greyish in colour, but in other cases the timber may only be marked with red spots. A test is to bore a gimlet or auger hole into the timber, and the appearance of the dust

so extracted, together with a peculiar fusty odour, will announce the presence of dry rot. Not only is it necessary to be sure that infected timber is not put into the Avork, but care must be taken that timber most liable to infection is avoided. Wet timber, unseasoned timber, and sappy timber should not be used. It should also be constantly borne in mind that all timber should be surrounded by a thorough circulation of air, and steps should be taken to exclude damp. Wooden ground floors are particularly liable to attack. The ground surface should be sealed with concrete, especially over a clay subsoil. Dampproof course should be provided to the walls and the ends of joists should not be pinned in. Air bricks should be provided in the walls under the floors and on opposite sides, so that a thorough current of air may be obtained, and care should be taken that the air brick openings are not fouled by mortar droppings as the walls are built. I have •seen air bricks completely blocked by the

last joist on each side of a floor. The bricks should be fixed lower, or the joists made to run the other way. In the absence of ventilation, and in the presence of damp, and particularly when the favourable conditions are increased by the proximity of stoves or kitchen range providing warmth, the germs of dry rot attack the timber, and become rooted in its surface, feeding upon and decomposing its fibres, and the gaseous products of decomposition which are given off but add to the favourable conditions. Dry rot once established spreads with great rapidity and is very difficult to get rid of, even when all decayed parts are removed and the conditions as to ventilation and dryness improved. In one or two cases which have come to my notice, a sound floor was eventually obtained by removing every vestige of timber and sweeping out the space beneath the floor, which was then coated in every part with hot limewash before fixing the new joists and flooring. The ventilation had been previously attended to, but before the drastic measures just mentioned the dry rot which destroyed the first badlyventilated floor immediately attacked the second floor which was laid down. The ventilation of floors it, not in all eases an easy matter, for many rooms exist which have on two of the four sides other

rooms with concrete floors. In .such instances, two air bricks in each of the remaining and adjoining sides may be fixed and the air circulation, though not perfect, is usually adequate ; but there is the instance, as in a row of cottages, where the front rooms have boarded floors and the kitchens behind them flagged or concrete floors. It is then only possible to fix two air bricks m one. the only, outer Avail, and this is not b> any means ideal ventilation. In all doubtful cases it is a very wise precaution to used creosoted joists, or they may be coated with "Solignum." The latter may also be applied to the undersides of the boards with, advantage. The use of linoleum on all floors subject to dry rot much increases the difficulty; but, provided a linoleum is laid on a floor without the edges being ( eniented down, and the floor is constructed of thoroughly sound material and the conditions of dr\ness and ventilation are perfect, there need be no fear of dry rot setting in. A floor composed of good materials but without ventilation and covered with an oilcloth,

was in such a state that, within three years of laying, the legs of the furniture went through both the linoleum and the boards j the joists also were in a very unsafe state. In the case of another floor where some unseasoned timber was used with no ventilation at all, and a linoleum was laid, dry rot was rampant in from six to twelve months. From the underside of this I stripped off a paper like fungus growth, which was very tough, and came away in pieces, over a foot super., but after a few hours' exposure to the air, the pieces I stripped off broke down into powder. The wood underlying the fungus growth had a brown, burnt appearance, and could be crumbled to pieces with the finger and thumb. Another instance is of an unventilated floor that had been down twelve years, and was not linoleum covered, which was so dry rotten that I went through it with both feet. It is, of course, impossible to foretell the life of a floor under all sorts of variable conditions, of bad material, and Avant of ventilation. Its life is very short, however. But if every care is exercised in these matters, a good floor will last a great number of years, even if covered by a linoleum which does exclude a certain amount of air, as, indeed, does a carpet, or any other covering.