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.