Slate Roof Headlap

For example a 10 inch by 20 inch slate requires 170 slates per square a square is 100 square feet of roof coverage when installed with a 3 inch headlap but requires 180 slates per square when installed with a 4 inch headlap.

Slate roof headlap.

Laying slate with appropriate headlap and offset helps to accommodate wind driven rain and the lateral movement of water below the slate shingles to prevent infiltration through the nail holes and side joints. Minimum headlap for fixing slates with nails or hooks the installation of a slate roof involves a number of aspects that must be considered in the design process. It describes not only the means of installing slates nailing or hook fixings but also the headlaps or lap required to ensure that the roof remains watertight even at pitches as low as 20 degrees. Generally speaking 20degrees is the lowest advisable pitch for a slate roof depending on the size of the slates and how much that the roof is exposed to moderate weather conditions.

Headlap and exposure are related to each other and the starting point for determining both is roof slope. Most significant is the environment with the two main factors being exposure to wind and rain. The primary aspects to be considered are. Headlap exposure and offset.

Headlap as defined in the national slate association s slate roofs design and installation manual 2010 edition is the length in inches of the upper portion of a roofing slate that is covered by the butt of the slate two course above. Furthermore you want to make sure the slates are manufactured with the nail holes in the right place. When slating with a shallow pitch a wide slate is highly recommended for maximum side lap or lateral lap side overlaps.