Flashing. Flashing is the term applied to the process of making a joint water-tight, by fitting tin, lead, zinc, or copper in such a way as to prevent the water from running into the joint. The flashing of slate roofs should be of copper, as the slate will, if laid properly, outwear all other sheet metals.
Fig. 123. - Repairing a Shin-gled Roof.
Fig. 124. - Shingle Nail Cuter.
Fig. 125. - Flashing a Dormer Window.
Figure 125 shows two methods of flashing around a dormer window, or any place where shingles or clapboards join a shingle roof. At a the flashing runs under the roof shingles and carries the water under the course of shingles above, causing them to decay more quickly than they otherwise would, while if flashed as at b the water will run onto the roof and away; a makes the better looking job, but b is the more satisfactory.
For flashing around a skylight, or any smooth wooden work, the sheet metal should be cut into the vertical side of the joint, as shown at a, in Fig. 126, and the top bedded in white lead, and nailed into the cut securely. At the upper side of the frame there should be a cricket, or saddle; this is a board, covered with sheet metal, for the purpose of shedding the water, as shown in Fig. 127. This saddle also should be placed behind chimneys, and all other places where a roof pitches toward a vertical or perpendicular surface. A brick chimney always should be counter flashed, as in Fig. 128. The flashing, a, should be carried under the course above, and nailed well under the butt of the next course, but not nailed to the chimney at all, as there is a certain amount of shrinking and swelling of the timbers of the house, as well as of expansion and contraction of the chimney, as it alternately heats and cools, besides the settling which always takes place in a new house. If the flashing is fastened rigidly to the chimney, a leak will probably occur sooner or later.
Fig. 126. - Skylight Flashing.
Fig. 127. - Saddle or Cricket Flashing.
In putting the counter flashing, b, in brick work, the mortar should be raked out, and the flashing metal entered at least ¾", and held in place by a metal wedge, or a hook-shaped tack made especially for that purpose. A 10d. common nail is sometimes used for the same purpose, the head holding the flashing in place, after which the joint is well pointed with elastic roofing cement.
At c is shown a third method, with the flashing resting upon the shingles. To repair the roof, the counter flashing may be lifted up, and the flashings easily removed, while by the other methods the flashing would be destroyed.
Flashing should extend not less than 3" above the roof in its lowest place, and in a pocket or place where snow is apt to accumulate, it should be high enough to insure that there will never be any trouble. Bo shingles should be laid over the metal, as the nail holes will cause a leak, though the flashing should extend under the shingles to the first row of nails,
Fig. 128. - Counter Flashing.
In fishing any but a very simple roof, there generally will be places where the soldering iron will have to be used, and the carpenter who neglects to have the work done properly will find that his reputation will suffer; the architect or owner may make him pay for any damage to the inside of the house resulting from a leak.