The ridges of the roof may be finished in two ways, either with the combed ridge or the saddle ridge. The combed ridge is formed by projecting a finishing course and a combing course of slate on the north or east side of the roof 1½ inches beyond the top and combing course on the opposite side of the roof. Both courses are laid with slate set lengthwise, the length being twice the width of the slate used on the roof. This last course is laid in elastic roofing cement, and the nails are also covered with it.
The saddle ridge is formed by alternately butting the ends of the top course on one side with the top course on the other, and then doing the same with the combing course. This makes a zigzag joint which is closed by the elastic cement used in setting.
The Boston hip is the best. Each course is brought at its upper or nailing edge to within 2 inches of the hip line. A small strip of slate then finishes this off by fitting to a mitre cut made on a slate set parallel with the line of the hip. These hip slates have the lower corner of their butt ends on a line with the next lower course, and they are lapped with the opposite hip slate and made tight with roofing cement.
SLATE ROOF
Hips may also be finished by bringing each course up to the hip line, and mitring them with the opposite courses on the other side of the hip.
Valleys should be lined with 16 ounces copper, 4 pounds lead, IX tin, or a prepared roofing roll weighing 37 pounds per 108 square feet. Measuring from the centre of the valley to the edge of the slate along the valley, this distance should be 2 inches at the top and increase ½ inch in every 8 feet length of valley, to widen it out toward the bottom. The flashing should extend up under the slate on either side about two-thirds the width of the slate used. If 8-inch by 16-inch slates are used, this means that the distance should be about 5 inches. If the slopes of the two intersecting roofs are different, and there is a chance that the volume of water sweeping down the larger and steeper incline may be forced up under the slate at the valleys, the metal lining should be crimped up (inverted V-shape) at the centre, 1 inch, to form a little dam against the rush of the flood.
SLATE DETAILS
Flashing used against chimneys, dormers, or other vertical walls should be bent up 4 inches and extend into the slate courses 4 inches. All vertical flashings against masonry should be cap-flashed and made tight with elastic cement. The cap-flashing should extend down over the flashing 3 inches, and be inserted into the masonry at least 2 inches.