Slate Roof Headlap

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.

Slate roof headlap.

When slating with a shallow pitch a wide slate is highly recommended for maximum side lap or lateral lap side overlaps. Most significant is the environment with the two main factors being exposure to wind and rain. Bs 5534 2014 is the code of practice for slating and tiling. Headlap exposure and offset.

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. The part of the lapping system where there are three layers of slate. Furthermore you want to make sure the slates are manufactured with the nail holes in the right place. According to an identification guide on the slate roof central website some of the hardest heartiest types are purple slate non fading green slate and grayish black buckingham slate which can.

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. 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. 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.