Roofing Slate Thickness

Posted By On 2 Aug 2017

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”.

Light weight roofing slate, 3/16" thick North Country Unfading Black
North Country Unfading Black slate, 3/16″

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.

North Country Unfading Black slate, 1/4" thick roofing slate
North Country Unfading Black slate 1/4″

When ordering the various slate thicknesses a 3/16” is called “Standards”, ¼” is “quarters”, 3/8” is “Heavies” and ½” is “extra heavies.

Heavy North Country Unfading Black roofing slate 3/8" thickness
North Country Unfading Black slate 3/8″

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.

Slate roof design and installation information for architects is available on our website, or feel free to call our office at Toll Free 1-800-975-2835.


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