Part 3 (1/2)
The presence of water in the soil has usually been considered to be unhealthy because of the impression that it led to certain fevers. The writer has heard, for instance, of an attack of malaria being caused by a short visit to a damp vegetable cellar; and it is one of the triumphs of the century that the malarial parasite has been discovered, and the old theory of the dangers of moisture been done away with. A damp cellar has always been considered to be undesirable, but just why n.o.body knows. A damp cellar causes molds to form rapidly, thus destroying vegetables and other material which might naturally be stored there, but that the presence of moisture in a cellar in itself produces any organic emanation leading to disease is not true, although dampness is essential to the growth of certain organisms.
In the latter part of the nineteenth century, Dr. Bowditch, of Boston, showed that consumption developed most where the surrounding soil was moist, and generally it is the impression that dry air is the only proper air for a consumptive person to breathe. This theory, however, is being rapidly exploded, and patients now remain outdoors in any weather, and no kind of air is objected to by physicians, provided it is outdoor air. Some little time ago the writer was called by a Board of Health to investigate a certain swamp which had some odor, was considered a blot on the landscape in an unusually picturesque village, and was said to be responsible for a long list of contagious diseases. A house-to-house inquiry in the vicinity showed that among some dozen families, only one illness in the last few years could be remembered, and that was an old lady who had been on the verge of the grave for forty years.
It is curious to note the many examples which are cited by the earlier sanitarians to prove the dangerous effect of damp soil. For example, Pettenkofer, a very prominent German hygienist, says that in two royal stables near Munich, with the same arrangements as to stalls, feed, and attendance, and the same cla.s.s of horses, fever affected the horses very unequally. In one stable, fever was continually prevalent; in the other, no fever was found. Horses sent from the unhealthful to the healthful stables did not communicate the disease. The difference between the two places, says Pettenkofer, was that in the healthful stables the ground water was five to six feet below the surface, while in the unhealthful ones it was only two and a half feet from the surface. A system of drainage by which the ground water was brought to the same level under both stables made them equally healthful. The writer cannot help but feel that some other factor was involved, and while he has no doubt that excessive dampness in stables or cellars is undesirable, he does not believe that such dampness can be directly the cause of fevers of any sort.
It is not desirable, however, to live over a wet cellar nor to maintain a house in a constant condition of dampness, partly on account of its bad effect on the house and partly because such dampness may, by reducing the vitality of the household, become a predisposing factor in disease.
_Drainage._
From whatever source dampness may come, it can be guarded against by giving to the surface of the ground in the vicinity of the house, on all sides, sufficient slope away from the walls so that there will be no tendency for water to acc.u.mulate against the cellar walls. On the top of a hill this is very easy to do, and the natural surface grade takes care of the surface water without difficulty. On a sidehill or in a valley artificial grading has to be resorted to, except on one side.
[Ill.u.s.tration: FIG. 3.--A grading that turns water away from the house.]
Too much emphasis cannot be laid on the necessity for grading the ground surface away from the house. In some cases it may be sufficient to dig a broad shallow trench protected from wash by sods (Fig. 3). In other cases it may be desirable to pave the ditch with cobble stones or to build a cement gutter. In constructing such a surface drain, proper allowance must be made for the acc.u.mulation of snow and the resulting amount of water in the spring, so that the distance in which the ground slopes away from the house ought to be, if possible, at least ten feet, so that there can be no standing water to penetrate the house walls. The slope necessary to carry surface water away need not be great. A fall of one foot in one hundred will be ample, even on gra.s.sy areas, and if the surface is that of a macadam road or the gutters of a drive, this grade may be cut in two. A slope of more than one foot in one hundred is permissible up to a maximum of seven or eight feet per hundred, more than this being aesthetically objectionable and tending to make the house appear too high. Whenever gutters are built in driveways or ditches to intercept water coming down the slopes, a suitable outlet must be provided to carry the water thus collected either into underground pipes, by which the water is led to some stream or gulley, or directly into some well-marked surface depression.
_Ground water._
The soil always contains water at a greater or less depth, and the elevation of this ”ground water,” as it is called, varies throughout the year partly with the rainfall and partly with the elevation of the water level in the near-by streams.
It is not at all unusual for this ground water to rise and fall six feet or more within the year, high levels coming usually in the spring and fall, and low levels in the late summer and winter. It is easily possible, then, that a house cellar may seem dry at the time of construction in summer and may develop water to a foot or more in depth after occupancy. The presence of such an amount of water in a cellar, whether injurious to health or not, is objectionable, and a subsoil trench should be provided in order to limit the height to which ground water may rise.
If a system of drainpipes is led around a house extending outward to include the surrounding yard, then the ground water will always be maintained at the level of those pipes, provided the system has a free outlet. Indeed, the question of an outlet for a drainage system is a most important factor, and no system of underdrains can be effective unless a stream or gulley or depression of some kind is available into which the drains may discharge. It is for this reason, quite as much as for any other, that the location of a house on a perfectly level bottom land is objectionable, since the ground there may be normally full of water with no existing depression into which it may be drained.
In the next chapter the proper method of laying drains close to the cellar wall, for the purpose of taking away the dampness from those walls, is described, but another system of drains is desirable, covering more area and more thoroughly drying the ground, provided the ground water needs attention at all. These drains should be laid like all agricultural drainage; and while subst.i.tution of broken stone, bundles of twigs, wooden boxes, or flat stone may be made, the only proper material to be used is burnt clay in the form of tile. These tiles are made in a variety of patterns, but the most common in use to-day is one which is octagonal outside and circular inside. They are about one foot in length and may be had from two to six inches inside diameter. The ordinary size for laterals is four-inch diameter, while the mains into which these laterals discharge are generally of six-inch diameter. These tiles are laid in trenches about fifteen feet apart, although in porous soil, such as coa.r.s.e sand or gravel, this distance may be increased to twenty feet. If the tiles are laid more than four feet below the surface, this distance may be increased, and if the tiles are five feet deep, the distance apart of the several lines may be fifty feet.
The grade of the line must be carefully taken care of, and while it is possible to lay a line of tile with a carpenter's level and a sixteen-foot straightedge, it is much safer to have an engineer's or architect's level and set grade stakes, as in regular sewer work. A fall of one fourth of an inch to the foot is a proper grade, although a greater slope is not objectionable. It is sometimes desirable in soft ground to lay down a board six inches wide in the bottom of a trench on which to rest the tile, but, unless the ground is very soft, this is not necessary. Care must be taken, however, if the board is not used, to have the bottom of the trench very carefully smoothed so that a perfectly even grade in the tile is maintained. There are three ways of laying out a line of trench as shown in the following sketches (Fig. 4).
It is usually sufficient to run parallel lines of tile from fifteen to fifty feet apart over the area which it is desired to drain, and let the ends of these lines enter a cross line which shall carry off the water led into it. This cross line should be six inches in diameter as a general rule, unless there is more than a mile of small drains, in which case the size of the cross pipe ought to be increased to eight inches.
This cross line then becomes the main outlet, and great care must be taken to see that it has a perfectly free delivery at all times of the year. In cities and sometimes in small villages it is possible to discharge this outlet pipe into a regular public sewer, provided the sewer is deep enough, and provided the munic.i.p.al ordinances allow such a connection. Otherwise, the outfall must be carried to a natural depression.
[Ill.u.s.tration: FIG. 4.--Modes of laying out drains.]
In level ground, the problem of finding a suitable outlet is a serious one, and in many cases impossible of solution, so that the householder, being unable to find an outlet, must put up with the ground water and be as patient as possible during its prevalence. It does not do to trust one's eye to find a practicable outlet, since even a trained eye is easily deceived. An engineer with a level can tell in a few moments where a proper point of discharge may be found, and it is absurd to begrudge the small amount which it will cost, in view of the large expense involved in digging a long trench to no purpose.
Some years ago the writer was able to note the conditions in a house where the cellar excavation went three feet into limestone rock. The strata were perfectly level and the cellar floor of natural rock was apparently all that could be desired, smooth and flat, without involving any expense for concrete. One wall came where a vertical seam in the rock existed, and since this natural rock face was smooth and vertical and just where the cellar wall should go, it seemed unnecessary to dig it out and lay up masonry in its place. So it was left and the house built. When the spring rains came, however, the cellar was turned into a pond, water dripping everywhere from the vertical rock face, and coming up through the cellar bottom like springs. It cost a great deal more then to make the changes and improvements necessary in order to secure a dry cellar than it would have done at the outset. This serves as an ill.u.s.tration of the need of taking every precaution at the beginning to insure a dry and well-drained soil around and below the cellar walls.
CHAPTER III
_CONSTRUCTION OF HOUSES AND BARNS WITH REFERENCE TO HEALTHFULNESS_
Any liability to disease that may come from faulty construction of habitations is likely to spring from a polluted subsoil. Such pollution vitiates the air drawn from that soil and is a source of danger on account of the resulting impurity of the whole atmosphere within the house.
_Shutting out soil air._
We have already seen (Chapter II) how it is possible for soil charged with organic matter to deliver, either through suction from a heated house or on account of a rising ground water, soil air into the cellar, and also that moist air may enter the house in the same way. In order to prevent this, it is plainly necessary to interpose some air-tight or water-tight layer between the house and the soil, and also, since perfection in this layer is impossible, to make provision for draining away any water which may acc.u.mulate against the walls. Ordinary builders do not lay much emphasis on the importance of either of these precautions, and while one may often see cellar walls roughly and carelessly coated on the outside, with tar or asphalt, a thoroughly water-tight coating is not a common practice. Similarly, while draintile are often laid around a house, they are either laid so near the surface as to be useless or else they have no porous filling.
[Ill.u.s.tration: FIG. 5.--Exterior wall-drains.]
To prevent moisture from entering the cellar, the first provision should be a tile drain (not less than four inches in diameter) laid completely around the house (see Fig. 5) on a grade of not less than six inches in one hundred feet. This drain at its highest point ought to be one foot below the bottom of the concrete floor of the cellar, and more than this, of course, at the lower end. This should be laid before or at the time the foundations for the house are being built, although it is possible to dig the necessary trenches and lay the tile after the house is built. If the available grade is small, this drain may be laid in two lines directly under the cellar floor as shown in Fig. 6. At the points _A_ the bottom of the tile should be at least a foot below the dirt on which the cellar floor will be laid, and at the point _B_, about two feet. This drainpipe is best laid with regular sewer pipe and without cement in the joints. Then coa.r.s.e gravel should be filled in around this tile so as to allow water to enter the pipe without carrying soil that later might settle in the pipe.