The first course of shingles at the eaves should be a double course with the upper layer breaking joints with the lower, and the shingles should project about 2 inches beyond the mouldings of the eaves and about 1½ inches beyond the edge of the gable ends of the roof.
Hips may be finished either with the saddle-board or with a row of shingles running parallel to the line of the ridge. Hips are best finished with a row of shingles running parallel with their edges, which treatment is called the Boston hip. If the courses are carried to the hip line and mitred, then the joint must be waterproofed by using tin shingles underneath the wooden ones, these tin shingles being folded over the hip. The method of flashing around chimneys, at the base of dormers, and in open valleys will be more fully discussed in connection with slate roofs, and, since the principles are the same, what is said for slate roofs in this connection is true for wooden-shingle roofs.
Method of Laying Roofs
SLATE
There has been much made of the so-called European method of laying slate roofs in recent years, but this type of roof costs more than the ordinary slate roof, since special heavy slate is used at the eaves, and the weathering is reduced as the courses approach the ridge, and special care is taken in blending colored slates. While this type of roof is very beautiful, it is really, from a point of view of cost, rather out of the race when applied to the small house, for it will be hard enough to stretch the estimates of the small house to include even the ordinary slate roof.
In the preparation of the ordinary slate roof, the rafters should be covered with ⅞-inch thick, tongued-and-grooved roofing-boards. In order to prevent buckling, if they should swell with dampness, it is essential not to drive the joints between boards up too tight. As these boards are surfaced only on one side, this side is laid against the rafters and the tongues are placed upward so that a better shedding of water is secured. Good nailing with tenpenny nails is important, and all joints at ends of boards should be made over rafters. A cheaper but not so good a bed for the slate can be made with common, unsurfaced sheathing-boards. In the cheapest kind of work sheathing-boards are not used, but only shingles lath.
Over the top of this rough boarding should be tacked 11 pounds per 100 square feet slater’s roofing felt, laid horizontally and lapping joints 3 inches.
The usual commercial sizes of slates are ³/₁₆ inch thick, and of the following standard sizes: 6 by 12 inches, 7 by 12 inches, 8 by 12 inches, 7 by 14 inches, 8 by 14 inches, 10 by 14 inches, 8 by 16 inches, 9 by 16 inches, 10 by 16 inches, 12 by 16 inches, 9 by 18 inches, 10 by 18 inches, 12 by 18 inches, 10 by 20 inches, 12 by 20 inches, 11 by 22 inches, 12 by 22 inches, and 12 by 24 inches. They have two holes in each piece for nails, which nails should be 1-inch copper slater’s nails, or 3d galvanized slater’s nails for cheaper work.
The first course should be started 2 inches below the line of the sheathing-boards at the eaves, and the necessary tilt is given with a ³/₁₆ by 1 inch cant strip. A double thickness of slate is used for the first course, the upper layer breaking joints with the lower. At the gable ends the slate should not overhang more than 1½ inches.
The exposure to the weather for courses of slate is determined by taking one-half of the length of the slate minus 3 inches.