ection 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.

[Illustration: 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.

[Illustration: 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
pro