No matter what sort of roofing material is used, do not forget the great importance of the roofing foundation (Figs. [296] and [298]). If the foundation is poor or uneven the roofing will be poor and uneven, even if only the best roofing material is used. The sheathing boards should be matched if possible and of uniform thickness, laid close, and free from nails, protruding knots, and sharp edges. Do not use green lumber; the sun is almost certain to shrink and warp it. Sometimes it will even break the roofing material. On very particular work, where the rafters are wide apart, the best builders recommend laying a course of boards over the planking at right angles to it.
Valleys
If there are valleys in the roof ([Fig. 298]) use a long strip of roofing and lay it up and down in the direction of the valleys. Press the strip into the hollow so that it takes the shape of the valley itself. Allow the edges of the roofing to overlap the strip in the valley an equal distance on both sides of the valley ([Fig. 298]).
How to Lay the Roofing
Begin at the eaves to lay the roofing ([Fig. 299]). Always lay the roll of patent roofing with the inside surface to the weather and in the same direction that the boards run—not at right angles to them. Begin nailing at the centre of the edges of the strips and work both ways to the ends—never the reverse, as the roofing may become wrinkled, twisted, or crooked. Always set caps even with the edge of the laps about two inches apart between their centres.
Gutters
To finish gutters, fasten and carefully cement with the pitch or tar or prepared composition the edge of the strip about half-way to the gutter. Bring the other edge onto the roof, then lay the next strip over this strip so that it will overlap at least two inches. Proceed to lay the balance of the roofing in the same way. Never nail the middle of the strips; nail only along the edges. The end strips should always be lapped over the edges of the roof and fastened (Figs. [297] and [299]).
Before fastening laps paint a two-inch strip with the tar or pitch cement which comes with all patent roofing in order to stick it to the lower strip of roofing and to make a tight joint when put in place.
Do not drive nails carelessly or with too much force and be sure the cap fits snugly against the roofing. If nails go into holes or open cracks, do not remove them but thoroughly cement around them. Allow six inches for overlaps for joints where one strip joins another ([Fig. 299], B). Be sure that two strips of roofing never meet at the ridge leaving a joint to invite a leak over the ridge-pole. Examine the diagrams if you fail to understand the description.
