The chief, if not the greatest, enemy of the builder is damp. It will ascend, descend, and penetrate - i.e., attack materials in all directions; and wherever it makes - or is allowed from inattention, carelessness, or want of forethought, in the first instance, to make - an inroad, it brings ruin to the building itself, in every manner, by sowing the seeds of decay; ruin to the furnishing and finishing of the building; and oftentimes ruin to the health of its occupants. Therefore it is the duty, and should be the chief care, of the builder to keep damp out, by one or other of the various means which will hereinafter be pointed out and explained.
This duty generally falls to the bricklayer and mason, except in so far as roofing is concerned, when it devolves on the carpenter, plumber, and slater; and all these will be dealt with, respectively, in their proper places. The bricklayer, however, is often really responsible for the decay of the carpenter's work from damp; though it should be the business of the latter, when possible, to see that due precautions have been taken with the brickwork before he puts in the woodwork which it is his business to attend to.
There are numerous methods of preventing the penetration of damp through the enclosing walls into apartments below the ground line: -
I. By building the walls of greater thickness, and setting the bricks in cement - a simple method, but often rather expensive; and, moreover, on valuable sites, a considerable quantity of room is sacrificed for this purpose, as compared with another mode of prevention which could have been used to greater advantage.
2. By hollow dry-area walls around the external faces, as illustrated by the section Fig. 186. This also is disadvantageous, for the same reason as method No. 1; and, in addition, care should also be taken that the cavity is thoroughly well ventilated, so as to maintain a current of air always passing through every part of it. Moreover, while providing such free and ample ventilation, every precaution must be taken to prevent any vermin harbouring in this cavity, as well as the accumulation of any refuse therein. The open area should commence from the footings, the bottom being paved in cement, and its walls built battering, in cement, from the bottom; and it should be wide enough to allow of its being cleaned out, when requisite. The top should be covered over with York slabs well secured together; or it should be arched over, as shown by dotted lines, which also is often done, in addition to the slabs. Through ventilation should be secured by ventilators at the top and bottom, the holes of the gratings, of course, being made very small in order to keep out vermin.
3. By lining the inside with a thin brick wall in cement, with a small cavity left between it and the main outer wall, as shown in fig. 187. This also takes up room, but otherwise is a good remedy. It is usually adopted for thick nibble stone walls, which are sometimes tarred before the brick-lining is built up securely, and free from ventilation. This method has the advantage also of being applicable to rooms above the ground floor line. The heading and bonding bricks should have their ends (which go into the stone wall) well tarred before being built in.
4. Another method is to run Hygean Rock asphalte, while hot, within the vertical joints of the enclosing thick walls. This is usually done about half a brick or 4 1/2 inches from the external face, the first vertical joint inwards, longitudinally, being left open, as shown in fig. 188. The asphalte is poured in at every three or four courses, filling up the crevice, and forming a complete coating inside the wall. This is a cheap method, but it is only applicable with advantage to brick walls; still, it is very effectual, and also very convenient and useful for the upper part of the wall.
5. To face the wall externally with blue-brick work, built and bonded in cement. This has been proved to be a simple and effectual remedy against the penetration of damp.
6. To render the external face over with cement and sand, about one inch thick. This is another simple remedy, which can be used both above and below the ground floor line; the upper portion admitting of treatment ornamentally, without any great expense.
7. The outer faces of the basement walls can also be coated with asphalte, laid on hot, about three-quarters of an inch thick; which, though very expensive, is the most effectual method of preventing the penetration of damp. Seysell and Val-de-travers asphaltes are the best for this purpose, and should be laid on by the company's own men.