Damp-courses, or damp-proof courses, as they are correctly termed, are inserted in buildings to prevent the damp from entering the upper portion of the walls. The wet can get into walls in three ways, namely, (1) from the top, this being avoided by building a coping of hard bricks set in cement, and a course of tile creasing.

(2) From the front, this being prevented by rendering with cement, hanging with tiles, and by other methods.

(3) By capillary attraction from the foundations, w hen these are laid in wet or damp soil, or when the top soil becomes soaked by rain. It is to the last-men-tioned conditions that damp-proof courses are applicable. Water is prevented from getting, by means of capillary attraction, into the upperportion of buildings, by inserting a layer of some impervious material about 3 in. above the ground level. Asphalt is the bast material that can be employed, as if any slight settlement should occur asphalteasily conforms to it without cracking; it should be used in two layers, making altogether about Jin. in thickness, so that any joins or faults in one layer may be covered over by the next. Sheet-lead makes a very good damp-proof course, as it entirely prevents any moisture from getting higher up the building: besides, it is pliable, and does not crack if any part of the wall should settle slightly more than another part. It is, however, too expensive for general use, and must belaid in cement. as ordinary lime mortar corrodes it very quickly. A stoneware damp-course of about 3 in. thick can be obtained with holes perforated through it so that it can also be used for ventilation purposes.

It costs more than asphalt, but it has the advantage of raising the building 3 in., thus saving one course of bricks; this may be deducted from the cost. Slates laid in cement are often employed as a damp-proof course; this, if the slates are laid in double courses so that each joint is covered by a slate, forms a very good damp-preventer, and is very cheap. It has the disadvantage, however, of being easily cracked, and this lessens its efficiency. A course of Staffordshire blue bricks can be built in the wall as the work proceeds, and these, if laid in Portland cement, make a very durable, permanent, and cheap damp-proof course.