The Modern Home
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The Treatment of Damp . •
DAMP walls are very much more than a menace to the decorations ; they are perhaps the gravest domestic danger to health that we are liable to encounter in these days of Sanitary and Food Inspectors. Unfortunately, one is liable to estimate their disadvantages entirely in terms of dimaged wallpaper and to ignore the less obvious but far more serious possibilities of damage to ourselves. Rheumatism—to which are attributed many cases of heart disease in later life—and various pulmonary disorders can all be traced to their baneful influence ; in addition to which they produce a definitely depressing atmosphere in any house where their presence is tolerated. One can safely say that a cure is always possible in any house that is not actually falling to pieces. The cost must vary widely in different cases ; but a really careful investigation of the causes will often point to some remedy far less expensive than might have been anticipated.
In the first place, a clear distinction must be made between damp which is the result of condensation and that which has actually penetrated through walls or roof. Given certain atmospheric conditions, condensation must be looked for on any cold, imporous surface such as paint, washable distemper (which I dislike for this reason) and, of course, glass or marble —particularly in any room which is not constantly heated. In this respect flatted paint is preferable to oil-bound. Occa- sionally one finds instances where an attempt has been made to cure a genuinely damp wall by stripping the plaster away and replacing it with cement. When this is papered it is found to be as damp as before, and the cement is held to be at fault. This by no means follows. In all probability the cement is perfectly water-tight, and the damp now showing is the result of condensation on its cold, non-absorbent surface. A thin skimming of plasterers' lime putty should have been put on before papering for the cure to have been effective. Condensation is a natural process which can only be circum- vented by the avoidance of cold, impervious surfaces in our houses or by keeping rooms and passages warm and well- ventilated. The capacity of air to carry moisture varies according to its temperature : and this iS an explanation of those warm, damp days which are usually described as " muggy." As the temperature falls, it reaches a point (known as " dew-point ") at which the air can no longer hold its moisture, and this is deposited on any colder solid, where, if it cannot soak in, it becomes visible. It is obvious that the cure of dampness from this source calls for remedies no more drastic than those I have suggested.
Structural dampness may be a more serious matter. It is gratifying to reflect that modern building methods can achieve greater immunity from damp with four inches of concrete than was possible to our ancestors with walls three feet thick or more. The great flaw in their practice was their failure to use the damp-course ; for the most part they seem to have been ignorant of the law of capillary attraction, which recognizes the fact, among others, that if a porous body such as a brick is allowed to stand in a shallow dish of water it will gradually become saturated far above the level of the liquid. The damp-course, which is a thin layer of waterproof material laid between two of the lowest courses of bricks in a building to prevent this process of absorption, is rarely found in any building more than a hundred years old, and has only been in general use for a much shorter period. Any case in which the dump appears to spread upwards from the ground-level points to a faulty or absent damp-course, and nothing that can be done to the outside of the house is likely to effect a cure. The insertion of a damp-course in an existing house is an expensive and troublesome business, necessitating the gradual cutting-away and relaying of at least two courses of bricks right round the house below the floor-level. In such a ease it may well be less expensive to waterproof the walls inside to a height above which the damp will not rise. If the damp-course is there, but has some defect such as a crack due to some slight subsidence of the foundations, it should be no great matter to effect a local repair.
If one knows what to expect, it is usually possible .to tell the causes of damp from the situation of the patches in which it first appears, and so to prescribe a remedy. One frequent source of mischief, for which the damp-course itself may be wrongly blamed, is the presence of soil resting against the outer wall* above the level of this. Many gardeners will. hink nothing of banking up a bed quite six inches above it, with the result that the damp has free access to the wall well above the barrier that has been carefully provided to keep it down. There should really be six inches clearance in a downWards direction so that any splashes from the ground may strike the wall well below the line. Where these:-precautions have been neglected for 'many years the lower bricks may have become porous through the continued action of rain and frost, and it may then be necessary to run a cement plinth, perhaps twelve inches high, along the bottom of the wall affected. This should be tucked well between the bricks at the top and should be sharply bevelled. Before deciding that this is needed, however, several months should be allowed for the wall to dry out after the first remedial steps have been taken.
Odd patches of damp appearing on the inside of a wall, unconnected with the positions of windows, eaves or chinineys, must mean that re-pointing is needed or that the bricks have perished and become porous. In the latter case it is quite possible that re-pointing alone will enable them to fulfil their function. It is important that the pointing be done in such a way that the face of the mortar slopes downwards and out- wards. If it is done " over-arm," the result is a narrow, horizontal ledge along the top edge of every brick, on which the water can lie. Cement mortar may be used with advan- tage, but it is rather more expensive than lime. If, in spite of re-pointing (and the replacement of any obviously faulty bricks) the wall continues damp, the bricks themselves must be deemed no longer capable of keeping out the weather, and steps must be taken to render them less porous. These need be neither expensive nor noticeable. G. M. BOUMPIIREY.
(To be continued.)
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