Head lap: Shortest distance from the butt edge of an overlapping shingle to the upper edge of a shingle in the second course below. The triple coverage portion of the top lap of strip shingles.
Interlayment is the installation of an underlayment (typically, felt paper) between each course of shingles. Interlayment is acceptable on a shake roof, but never on a wood shingle roof.
Skip-sheeting, or spaced sheathing, is just as it sounds: sheathing with gaps between. Traditionally, skip-sheathing consists of 1 inch by 4 inch boards nailed to the rafters with gaps between the boards. Spacing between boards is optimal for wood shakes but cannot support asphalt composite shingles.
Noun. interlayment (countable and uncountable, plural interlayments) (roofing) a felt, metal, or membrane sheet material used between courses of steep-slope roofing to improve the weather and water-shedding characteristics of the primary roof covering during times of wind-driven precipitation.
Cedar shingles should lap at least 18 cm (7 in.) over each side of valley flashing.
Both OSB and plywood panels can cut and installed on a roof using conventional roofing equipment. They have similar structural characteristics, and can be used interchangeably.
Spaced Sheathing, also called Skipped Decking, refers to the construction details of the substrate which the cedar gets nailed to and thus secured to your home.
Shingles should overlap the valley lining by at least 6 inches. With a roll roofing valley, keep the nails at least 6 inches from the valley centerline.