Читать книгу Rural Hygiene - Henry N. Ogden - Страница 23

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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 accumulate 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.

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 coarse 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.

Fig. 6.—Interior cellar-drains.

Position of outfall.

There is always a question of where this drain shall end and into what it shall discharge, for in some soils this drainpipe may discharge continually. To allow the drain to empty on the ground means that its outer end will be broken; that if discharge takes place just before freezing weather, the drain will fill with ice and be broken, so that some other method must be devised. If the outer end can be laid into a brook where the velocity prevents the water from freezing, or where the outer end can be kept below water, a satisfactory disposal is found. Otherwise, it is better to discharge into a small covered cesspool, provided the soil is sufficiently porous to take care of the water, and provided the level of the ground water allows the construction of such a cesspool. In any case, it should be at some distance from the house, so that if it overflows, the water will not seep back to the cellar walls. By water-proofing the main wall and then backfilling against the wall with coarse gravel or broken stone, the same results as with open areaways are obtained and at a much smaller cost.

Dampness of masonry walls.

One fact peculiar to all kinds of masonry and known to all careful observers is that stone work, brick work, and concrete will allow dampness to permeate, whether it comes from water-bearing soil or a driving rain. One objection to concrete-block houses has been that a hard rain would cause moisture to form on the inside. Brick buildings have the same defect when the walls are built solid.

An air-space in the cellar walls is the only way of insuring a dry cellar, if the bottom of the cellar is below the level of the ground water. A four-inch course of hollow brick may be used on the inside, or the wall may be actually divided into two walls with a space between.

Fig. 7.—Wall modes of making air-space.

Figure 7 (after Warth) shows three different ways by which an air-space is secured and the two component parts of the wall held together. In the top view, the two walls, one eight-inch and one four-inch, are held together by wire ties, leaving an air-space of about four inches. In the middle drawing the walls are tied together by making the air-space three inches wide and then lapping the brick laid as headers over both walls. In the bottom view special terra-cotta blocks are used which pass through both walls. There can be no question of the value of such construction in eliminating dampness from the inside wall, but, it must be admitted, the cost of the walls is increased somewhat.

Use of tar or asphalt on the wall.

Instead of an open space, nowadays, it is more customary to thoroughly plaster the outside of the cellar wall, and then paint it with a tar paint put on hot, which will adhere fairly well to the cement or masonry. Asphalt cannot be very readily used for this purpose unless it is an asphalt oil with but little bitumen paste. A paving asphalt, for example, even applied hot, does not adhere to the masonry, but slides down the walls as fast as it is applied. A successful method, however, of using such asphalt is to build the cellar wall in two parts, separated about half an inch, and filling in the intervening space with liquid asphalt. In this way, the asphalt is held in position, and is an absolute prevention of dampness.

Another method used successfully in the construction of one of the large railroad stations in Boston consists in painting the outside of the wall with tar and then pressing into the hot tar several layers of tar paper, the separate sheets overlapping in a special coating of tar. These sheets are thus made continuous around the building and under the basement so that no water can enter the building.

Fig. 8.—Water-tight wall.

A cross-section of one of the depressed tracks entering the Boston Station is shown in Fig. 8. The heavy black line represents ten thicknesses of tar paper, each one thoroughly painted with a thick paint of hot tar. It should be noticed that this water-tight coating is inclosed between masonry walls, so that the coating cannot be injured.

It is possible theoretically by these methods to build an underground cellar so truly water-tight that it could be set down in a lake, where it might float like a boat and not leak a drop, and there may be some locations that require such construction, such as a low river valley or an old salt marsh or a city flat, where no adequate drainage is provided. But practically such construction will always be found expensive, and is, in most cases, unnecessary and ineffective, as already indicated, and where the percolating water cannot be tolerated, involves the installation of some kind of pump to throw out the water that will inevitably, in larger or small quantities, pass through the best water-proofing. It is, therefore, the part of wisdom to place reliance on draining the water away from the house rather than on water-proofing the cellar wall.

Dry masonry for cellar walls.

It may not be out of place to add a word of caution against the practice of building cellar walls of loose stone, without mortar. They make no pretense of being water-tight, they offer no resistance to the entrance of rats, and they soon yield to the pressure of the earth and present that wobbly, uncertain appearance of cellar walls seen in rural districts. Nor should the idea that the interior is to be visible and the exterior invisible blind the builder to the fact that it is far more important to have the outside smooth. If smooth, there are no projecting surfaces for water to collect in, no edges for the frozen earth to cling to and by expansion tear off from the wall. If smooth, the joints in the masonry can be pointed or filled with mortar, and thus a suitable surface for the tar or asphalt is provided.

Fig. 9.—Rough-backed wall.

In Fig. 9 (after Brown) is shown a cellar wall with rough, irregular back, and it is easy to see how water would readily find its way down to one of the projecting stones and then along such a stone, through the wall into the cellar. With such a wall the action of the frost is more severe than with a wall with a smooth back, so that the wall in Fig. 9 is gradually pulled apart by alternate freezings and thawings. Figure 10 (after Brown), on the other hand, shows the cellar wall as it should be with smooth, even exterior, along which the water passes easily, with gravel backing, through which the water escapes to the drainpipe.

Fig. 10.—Even-backed wall.

Damp courses in walls.

Fig. 11.—Four modes of making water-proof cellar walls.

Another important means of keeping moisture from the cellar walls is to provide what is called a damp course at about a level with the top of the cellar floor. Where the soil is naturally damp, and where the cellar wells are not adequately water-proof, a second damp course should be provided at the level of the ground so that moisture from the damp cellar walls may not pass up into the above ground portion, which is naturally dry. These damp courses, in their simplest form, consist in bringing the masonry level around the building, and painting the top surface with liquid coal tar.

Fig. 12.—Waterproofing of cellar walls.

Another method is to paint the masonry with liquid asphalt, and then imbed in this paint a thickness of asphalt-covered building paper which is again painted with asphalt. This may be done in the horizontal layer where it could not conveniently be done vertically.

Four different ways used in France for securing dry cellar walls are shown in Fig. 11. The heavy black line represents the damp course, which, when added to the effect of the interwall space, which is shown in all the drawings but the first, and there replaced by a deep drain, insures absolute freedom from all moisture within the cellar. Figure 12 shows sections recommended by Dr. George M. Price, and indicates clearly the location of the damp course.

The cellar floor.

The floor of the cellar, in the same way, must be kept from dampness, and this is best done by covering the cellar floor with a layer of concrete, one part cement, three parts sand, and six parts broken stone; or, one part cement and eight parts gravel may be used. Care should be taken, however, that the gravel does not contain an excess of sand, and it is always well in using gravel for concrete to check the proportion of these two materials. This may be done as follows: Sift the gravel through an ash sieve so that it is free from sand; fill a ten-quart pail even full with the gravel and then pour in water to the top of the pail, keeping account of the amount of water poured in. This volume of water gives the proper amount of sand to use with the gravel for concrete, and if more sand than this was present in the original gravel, it should be sifted out until the proper proportion is reached.

Concrete is not water-tight, and the concrete floor of the cellar must be treated in some way to prevent water or moisture rising through this floor. One method is to cover the concrete thus laid with a denser mixture of cement and sand, put on three fourths of an inch thick, and made by mixing equal parts of sand and cement; or the asphalt layer already referred to in the cellar walls may be carried across the cellar, putting, as before, a paint layer on the concrete, then paper, then another paint layer, making it continuous and without a break from outside to outside. On top of this, to prevent wear and tear, a floor of brick, laid flat, or a two-inch layer of concrete may be laid.

Cellar ventilation.

The great importance of the cellar as that part of the house where, if anywhere, unhealthy conditions exist, justifies this prolonged discussion, and before leaving the subject, ventilation in the cellar should receive a word of encouragement. Too many cellars are damper than need be, are musty and close, full of odors of decaying vegetables and rotting wood, entirely from lack of ventilation. The cellar windows are small and always, closed. The cellar door is seldom opened, and never with the idea of admitting air. The impression on entering such a cellar is of a tomb.

The cellar, even in that part devoted to storing vegetables, needs ventilation as much as the house does, for the cellar air finds its way up into the house, and an unventilated cellar means a house with air deficient in oxygen and overloaded with carbonic acid, a condition which causes pale faces and anæmic bodies. Far better and healthier is it to open all the cellar windows, covering them with coarse netting to keep out animals and with fine netting to keep out insects, and let the disease-killing oxygen and sunlight in. Malaria comes from the cellar, whenever the malarial mosquito can find there a breeding place. The writer has seen many cellars in which mosquitoes were living the year through in entire comfort, utilizing the moisture and warmth of the cellar to enjoy the winter months and up and ready for their mission at the first sign of spring. A cistern in the cellar is objectionable on this account, and if one exists, it should be covered with mosquito netting.

The old-fashioned privy.

Another source of ill-health as well as of temporary discomfort is the typical construction and continued use of an outside closet or privy. The physical shrinking from the use of the ordinary building is most reasonable. As generally constructed, great draughts of air (presumably for ventilation) are continually passing through the small building, and when the temperature of the outside air is at zero, or thereabouts, only the strongest physique can withstand the exposure involved without serious danger of consumption, influenza, and pneumonia, or at least inviting those diseases by reducing the vitality of the body. Two improvements suggest themselves and should be put into effect wherever this primitive construction must continue to be used.

In the first place, the building itself should not be fifty or a hundred feet away from the house, so that every one is exposed to rain, snow, slush, and ice in making the journey thither. But some corner of the woodshed or barn should be utilized or the small building should be moved up by the back door and connected therewith by a roofed passage. The barn location is objectionable if it involves outdoor exposure in going from the house to the barn. A liberal use of earth in the privy vault will eliminate odors, and a water-tight box or bucket makes a frequent removal of the night soil practicable.

In the second place, a small stove ought to be provided to warm the closet in the coldest weather. Then the dislike to suffer from the cold, which leads so many to postpone nature's call, will be avoided, and the consequent digestive disorders which come from constipation and intestinal fermentations prevented.

Cow stables.

In matters of health, aside from ventilation, which is discussed in the next chapter, there is little to be said concerning the other buildings on the farm. Barns for hay are not involved. A few words may profitably be devoted to barns for stock, involving, as they do, by their construction, the health of the stock. One enthusiastic farmer writes that it is possible for farmers to keep their stock at all times under conditions which are an improvement upon the month of June. He believes that the cow stable should be as comfortable for the cows as the house is for the owner, subject to no fluctuations of temperature, and that, in this way, the health as well as the comfort and milk production of the cows would be maintained.

Light should be listed as the first essential of healthy stables, light to kill disease-producing bacteria, to make dirty corners and holes impossible, and to react on the vitality of the animals. Compare this with some stables where fifteen, twenty, or thirty head are stabled in an underground dugout with two or three small windows not giving more than four square feet in all. Stable windows should be set, like house windows, in two sashes and capable of being raised or lowered at will. In winter a large sash may be screwed over the regular window to keep out frost and moisture, provided there is some independent method of ventilation.

For good healthy conditions, a cow needs about 500 cubic feet of space, with active ventilation. In old stables, with poor construction, as little as 200 cubic feet per cow was allowed, and when stables were made tight with matched boards and building paper, 200 cubic feet was found to be too small, and it was recommended that one cubic foot be allowed for each pound of cow. But when tried by wealthy amateurs, it was found that this was too large; the stables were damp and cold in winter and became a predisposing factor in the development of tuberculosis. Between the two extremes, 200 and 1000, is the practical average named above, namely, 500 cubic feet of air space for each cow.

For the health of the cow as well as for the good quality of the milk the stable should be built with special reference to being kept clean. The ceiling should be dust-tight, so that if hay is stored above, it will not sift through. The part of the barn where the cows are kept should be separated from the rest of the barn by tight partitions and a door into the cow stable. Nothing dusty or dirty should accumulate. The floor of all stables for cows, horses, hens, and pigs should be of concrete to insure the most sanitary construction. Planks absorb liquids and wear out rapidly under the feet of the stock. Concrete can be kept clean, is nonabsorptive, and if covered with some non-conducting material, like sawdust, shavings, or straw, is a perfectly comfortable floor for the animals.

Use of concrete.

No development of recent times has tended more toward the improvement and greater comfort of house building than the use of concrete. In the earlier houses, the cellar walls were so badly built and the connection between the top of the cellar wall and the timber sill of the house was so poor that the winter's wind blew through above to the manifest discomfort of those in the house. The writer remembers sitting in the best room of a well-to-do farmer, and watching, with great interest, the carpet rise and fall with the gusts of wind outside. To avoid such unhappy consequences, farmers have been accustomed to bank up the house outdoors in the fall with dry leaves, spruce-boughs, or manure, usually to a point on the woodwork. This, of course, closes the cellar windows for the winter for the sake of keeping out the wind. A concrete wall, at the present price of cement, using gravel for the mixture instead of stone, need cost but little more than the price of the cement and the labor involved, and a tight cellar wall may thereby be obtained.

If the soil in which the cellar is dug is firm enough, the outside of the excavation can be made so that no form on that side will be required, but it is always better to make the excavation about two feet more than necessary, to put forms inside and outside, and, after their removal, plaster or wash the wall with a thick cream of cement and water. In carrying the wall above the ground, forms must be used with great care to secure a smooth surface, and Fig. 13 shows two methods suggested by the Atlas Cement Company.

Fig. 13.—Cellar-wall forms.

There are so many forms of construction where concrete is not merely a convenience but a great advantage in the matter of health around the house, and particularly a house in the country, that there would be no end if one once began enumerating and describing the various methods and processes involved. Besides the cellar walls and cellar floor, there are outside the house, silos, manure bins, walks, curbing, steps, horse-blocks, hitching and other posts, watering troughs, and drainpipe, all successfully made of this useful material. In the barn, the barn floor, the gutters, the manger and watering troughs, cooling tanks, and sinks are also made of cement. While it is possible to differentiate between the methods and the mixtures for these various purposes, it will not be greatly in error if the construction always follows the following principle.

Use enough cement to fill the voids in the gravel or in the sand and stone mixture employed, and have enough sand in the gravel or with the stone to fill the voids in the stone. This is readily determined, as already suggested, by the use of water. The water, which will occupy the voids in the stone, represents the necessary sand. When this amount of sand and stone is well mixed, the water then permeating the interstices represents the necessary cement, though it is a good plan to add about 10 per cent extra to allow for imperfect mixtures.

The mixing should always be done so thoroughly that when put together dry, no variation can be seen in the color of the mixture. It is surprising to see how readily a streak of unmixed dirt or of unmixed cement can be detected in a pile by the difference in the color which it presents. Such mixtures should always be made dry first and then the water added and again mixed until the result is of a perfectly firm consistency. Such a mixture can be applied to any of the purposes mentioned, and, in general, it is better to have too much water than not enough. The only difficulty with a very wet mixture is that the forms require to be made nearly water-tight, whereas with dry mixtures the same attention to the forms is not necessary.

If the concrete is to be used in thin layers, as in pipe or watering trough, where a smooth surface is wanted, better results are usually obtained by using a dry mixture and fine gravel and tamping the mixture with unusual thoroughness. It is always unsafe to smooth up or re-surface a piece of concrete. The difference in texture of the surface coat causes it to expand and contract differently from the mass of concrete underneath, and inevitably a separation occurs. If it is desired to put on a sidewalk, for instance, a smooth top coat, the consistency of the two kinds of concrete should be alike, and the top coat should be applied almost immediately after the bottom layer is put in place. Where concrete is used to hold water, a coat of neat cement should always be put on with a broom or a whitewash brush, mixing the neat cement with water in a pail, and it does no harm to go over the surface three or four times, the object being to thoroughly close the pores in the concrete.

For floors of cellars or barns, the dirt should be evened off and tamped and then the cement concrete should be spread evenly over it, and tamped just enough to bring the water to the surface. When partially dry, a better finish is obtained by lightly troweling the concrete. In a cellar or barn, it is not necessary to divide up the area into squares or blocks as is done with sidewalk work, but the entire area may be laid in one piece. In order to keep the surface level, however, it may be found convenient to lay down pieces of 2" x 4" scantling, the tops of which shall be on the desired level of the finished floor. By filling in behind these scantlings, which can be moved ahead as the filling progresses, the exact level desired can be obtained. Usually four inches thick will be a proper depth of concrete for this purpose.