DRY ROT IN HOUSES

Evening Star, Issue 22681, 22 June 1937, Page 2

DRY ROT IN HOUSES

RESULT OF SIX YEARS' RESEARCH Six years ago a special experimental liou.su was erected at the English Forest Products -Research Laboratory for tbo study of dry rot, and a report giving results of tho investigations has been issued by tho Department of Scientific and Industrial Research (Forest Products Research Record 14, ‘Dry Rot Investigations in an Experimental House'). Tho_ building is of brick and lias two stories. The ground floor, consisting of three experimental rooms and the laboratories, was used for tho experiments, and the floors of all the rooms were infected by nailing to a floorboard or joist pieces of wood infected with dry rot fungus. Tho floors were examined at intervals and tho results are conclusive in showing that, if a floor has been well constructed with proper ventilation dry rot fungus will not develop, even if active infection of the most virulent type is introduced. “It is thus evident,” tho report states, “ that it is more important that the construction of the building should bo well designed than that the timber should be absolutely free of infection. It is, of course, highly desirable that the timber should bo as far as possible free from infection, in case any subsequent leakage or accumulation of moisture should occur which might favour its development, It is, however, absolutely essential that in designing a building the precaution should be taken of ensuring that no moisture reaches any timber that is not thoroughly treated _ with preservative, since fungal infection is certain sooner or later to appear on any timber remaining in a condition suitable for its development.” GOOD AND BAD FLOORS. From the experiments with solid floors it is concluded that a certain amount of moisture slowly penetrates through even the best mixed concrete, and it is essential to provide a continuous layer of completely waterproof material between the concrete and the boards to act as a damp-proof course. Where this has not been done and the floor is covered with linoleum, or a similar impervious covering, moisture will accumulate and tho floor will become sufficiently damp for decay to arise. With a floor properly constructed, on lines suggested in the report, it is usually quite safe to lay linoleum. The washing of linoleum on solid floors, however, particularly if it is worn, should bo avoided as far as possible, as any water which penetrates through joints or cracks in the covering may have difficulty in escaping. It is better to keep the linoleum oiled or waxed. The typo of floor, the report continues, to which tho boards are nailed directly to battens embedded in concrete is a thoroughly bad one, and numerous instances of decay of such floors have been reported to the laboratory. It has been found that the insertion of a damp-proof course of bitumen between the boards and concrete provides a floor which, under the conditions of the experiments, is immune to dry rot except when fungus spreads from decayed floors adjoining. Bitumen should bo'' laid directly beneath the boards. Severe decay occurred in the floor where tho boards were laid on 2in of breeze concrete below which was the bitumen damp-proof course. In tho experimental room with a badly constructed hollow floor growth of dry rot soon • started from the infected boards and spread fairly rapidly over tho boards amt joists, particularly in the inner half of the room. In the room with a properly constructed and ventilated hollow floor no growth whatever of dry rot fungus developed in tho

floor, although each section was infected three times by bringing into contact with the underside of the floor wood on which dry rot was in active growth. The boards remained absolutely sound, and were perfectly clean and bright when, examined three years after the house was completed.