This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
The improvement of the woodwork of a house need not be considered in detail. Internal doors, stairs, etc, are rather matters of taste than of sanitary importance, and the repair of windows and other joinery can usually be entrusted without much misgiving to any intelligent workman; there is, however, one important question which must be discussed, as it is one which often arises, and which is not always easily settled. I refer to the question of dry-rot.
Dry-rot, as explained by the writer on page 153, vol. i., "is a kind of decay caused by the development of a fungus, the Merulius lacrymans, four conditions favouring the growth, namely - stagnant air, dampness, warmth, and absence of light or sunshine". There can be no doubt that the nature of the wood has also a great deal to do with the inception and spread of the disease. I know a ease where wood joists are laid actually on the earth and covered with floor-boards, and after a generation no trace of decay is visible; on the other hand, I have known several cases of dry-rot occurring in floors over basements. In one of these latter cases the joists were not plastered beneath, but the decay commenced at the ends, which were built into the wall at a point where this was below the external ground. Damp and sappy wood is particularly liable to dry-rot, and should not be allowed in new work.
The practice, common in some parts of the country, of laying stone flags or concrete on the top of a joisted and rough-boarded floor, cannot be too strongly condemned. I have known a floor of this kind collapse within two or three years of its construction: on the other hand, it must be confeased that some floors, constructed in this way forty or fifty years ago, are still apparently as sound as ever. It appears to me that, in these days of cheap contract-work, the quality of the wood used by builders is far inferior to that used a few generations ago, and to this, as much as anything else, must be attributed the greater prevalence of dry-rot. which is found to-day not only in the cottage and cheap villa, but in the mansion and palatial town-hall.
To prevent dry-rot in floors is easier than to cure it. Ventilation must be secured, not only beneath the joists, but also around their ends. This can only be effected by providing sufficient air-grates beneath the floor, particularly in the angles of the room, and by allowing the ends of the joists to rest on offsets of the wall, as shown in Fig. 21, page 72, vol. i., or by leaving a space in the brickwork around the end of each joist; the former is the safer plan. Sometimes special air-ducts must be formed under neighbouring solid floors in order to ventilate the inner angles of rooms; an example of this kind is illustrated in figs. 683 and 684. Care must also be taken by the householder lest the grates provided by the architect be covered with litter or garden-mould; at least one case of dry-rot, due to neglect of this simple precaution, has come under the writer's notice.
Fig. 683. - Plan showing Ventilation of Space under Wood Floor AAA, air-grates: B. air-opening; CC, air drain under solid floor.
Fig 684. Enlarged Section at cc.
The cure of dry-rot is often a very difficult matter. In its early stages, dry-rot may sometimes be prevented from spreading, by thoroughly scraping and drying the wood, and covering it with some antiseptic solution, such as carbolineum avenaiius. Probably the mischief has begun at the ends of joists inserted in a damp wall; if so, the walling around must be opened out, and the wood carefully treated. In bad cases the only remedy which can be recommended, is the radical one of removing the floor, thoroughly cleaning the walls and space beneath the floor and washing them with "hot lime so as to destroy all spores, and laying a new floor of better materials.
No cure can be permanent, however, which does not include the provision of sufficient air-grates suitably placed beneath the floor, and the prevention of dampness, especially in the walls at the ends of the joists.
While dry-rot usually occurs in situations alternately moist and dry, wet-rot is caused by excessive dampness, and is often seen in window-talk, fence-posts the feet of door-posts, and other exposed woodwork. It doet not spread with the rapidity of dry-rot, and the cutting out of the affected piece and replacing with new are not usually laborious operations. Where the ends of beams have begun to decay, brackets can sometimes be secured to the wall beneath and the decayed parts cut away, as shown in Fig. 685.
Old wood floor-boards are often warped, and the joints so open as to hold a large quantity of fine dust Planing will do something towards levelling the surface, and the widest joints may be filled with strips of wood, while the remainder may be stopped with putty. The floor can then be stained and varnished. In bedrooms especially floors finished in this way are desirable, on the score of cleanliness and convenience. Better surfaces can, of course, be obtained by covering the floors, after levelling, with thin parquetry,which can now be obtained in removable slabs. Cork carpet, glued to the floor after this has been planed, also forms a satisfactory surface, which can be easily washed and does not need removal. Paints of various kinds are well-known preservatives of wood, the paint most commonly used consisting chiefly of white-lead, oil, and colouring matter. Taints with a base of zinc-oxide are, from a sanitary point of view, far preferable to those containing white-lead, as the latter are a certain cause of illness and premature death to the artizans who are regularly engaged in manufacturing or using them, and sometimes during drying cause sickness among the occupants of the building where they have been used.
Fig. 685. - Bracket to support End of Beam with decayed part cut away.