Roofing Slate Thickness
The most common thickness is ¼” and weighs approximately 935 pounds per square when installed with a 3” headlap. Some quarries such as Glendyne, which produces our North Country Unfading Black slate can be split consistently and sold 3/16”, ¼”, 3/8” and ½”.
When selecting a slate thickness, there are a few things you should consider such as the weight per square. A 3/16” thick slate weighs approximately 700 pounds per square whereas a ½” thick slate weighs approximately 1870 pounds per square. Thicker slates are also more expensive and have more texture to the face of the slate.
When ordering the various slate thicknesses a 3/16” is called “Standards”, ¼” is “quarters”, 3/8” is “Heavies” and ½” is “extra heavies.
When a roof has several slate thicknesses installed, this is called a graduated slate roof. The thicker slates are installed at the eave and the thinner slates at the ridge.