Copper Flashings - A Manual - 1925 - Page 12
Fig. 32. When forming a "closed" valley with small sheets of copper the method shown in Fig. 32 is used. The size of sheet used is determined by the length of shingle and the pitch of the adjoining slopes. Each sheet should extend at least 2 inches above the top of the shingle on which it rests so that it may be nailed along the upper edge to the roof sheathing and not through the shingles. Each sheet should be long enough so that it will lap the one below at least 3 inches, but always set back of the butt of the shingle above so that the copper will not be visible. Each sheet will then be separated from the sheet below by a course of shingles. (See Section A-A.) The sheets must be wide enough so that the vertical distance from the bottom of the valley to a line connecting the top of the sheets (see Section B-B) will be at least 4 inches. The sheets should be nailed only at the upper edge with copper nails, and laid at the same time as the shingles. Some roofers prefer to bend these sheets with a center "crimp" (see D-D, Fig. 33) thereby stiffening the sheet, forming a straight line to which to set the shingles, and preventing the possibility of water from one slope being forced above the flashing on the opposite slope when the drainage from one slope is greater.
Fig. 33. Another method of forming a "closed" valley is shown in Fig. 33. In this method the copper is laid in long narrow sheets directly on the paper or felt covering the roof sheathing and before any of the shingles are laid, except the first course at the eaves. The copper sheets may be of any length desired but the upper sheet should lap the one below at least 4 inches, unless the lap is soldered, in which case the lap may be reduced to 1 inch. Each sheet should be nailed about every 18 inches along the outer edge of its long dimension, and be wide enough so that the vertical distance from the bottom of the valley to a line connecting the tops of the sheets (see Section D-D) is at least 4 inches. In laying the shingles on top of this flashing great care must be taken not to drive any nails through the flashing. The "crimp," as shown in Section D-D, Fig. 33, has its uses as explained in Fig. 32, but the flashing may also be made in the shape shown in Section B-B, Fig. 32.
Fig. 34. A factory saw-tooth roof presents many problems. In order to obtain maximum light and at the same time avoid direct sunlight, the roof windows are placed facing in a northerly direction. This means that the gutter is always in shadow, which, in northerly localities, permits the snow to gather and remain in the gutter for long periods. The "line of minimum shadow" shown in Fig. 34, indicates the point down to which the sun shines on the slope of the roof. The area to the left of this line receives more or less sunlight according to the hour, and the area to the right receives none. This line as well as the angle of the face containing the windows varies with the design of the building and the latitude in which it is built. In every case the copper flashing should be carried up the slope at least 1 foot beyond the minimum-shadow line and be fastened to the roof by cleats and also be carried up under the sills of the windows. All sharp angles should be avoided in the construction of gutters, and in those over 24 inches wide a soldered lock seam should be formed length- wise down the center to allow for expansion and contraction.
Gutters of this type are usually subject to hard treatment as it is often necessary to shovel out the accumulated snow. When this is done the metal is often broken by the shovels or punctured by the heels of the workmen. To overcome this different schemes have been tried. Steam coils for melting the snow are probably the best. In every case there should be provision for quick drainage. Small electric heaters are sometimes placed at outlets. Sometimes a steel angle, about 5 inches by 5 inches, with edge notches, is placed inverted in the middle of the gutter. The water from melting snow flows through the small notches to the outlets, and the snow is kept thoroughly drained.
If the gutters are to be cleared of snow by workmen with shovels, snow boards are absolutely necessary.
Two methods of flashing the ridge of a saw-tooth roof are shown in Fig. 34. The one at the left is for a shingle roof above a copper-sheathed wall and the one at the right for a shingle roof over a shingle wall. In each case the edge is turned back ½ inch to provide stiffness.
Fig. 35. In building a gutter for a saw-tooth roof it is very important to avoid all sharp bends of the copper, to avoid sudden drops, provide an easy flow for the roof water, and to carry the flashing high enough to avoid chance of overflowing behind it. Fig. 35 shows a gutter where many of these important features have been omitted. The short distance that the flashing has been carried up on the roof and walls is a constant source of leakage in case of the temporary stoppage of the gutter outlet. The sharp angles at the bottom of the gutter will be a likely place for a crack in the copper to occur through expansion, and the vertical drop of several inches from the sloping roof to the bottom of the gutter will cause wear by erosion. All these points may be avoided by proper design.
Fig. 36. Another correct method of forming a gutter for a saw-tooth roof is shown in Fig. 36. Note that the course of the drainage water is changed gradually instead of abruptly as in Fig. 35, that all sharp angles in the copper are avoided and that the flashing is carried up on the walls and roof high enough to avoid any chance of an overflow caused by stoppage of the leader outlets of the gutter.
Scuppers should be provided at the ends of gutters of this type. They provide an overflow in case the leaders become obstructed, and give timely notice of a stoppage before any material damage has been done.
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