When it comes to a traditionally installed slate roof, weights can vary from 650 to 2,500 lbs per square depending on your thickness requirements and design needs. New lightweight systems now offer installation alternatives to meet weight requirements of 550 lbs per square using real natural slate. If you prefer a traditional installation, you may want to consider a thinner, lightweight slate. When it comes to splitting the various thicknesses, not many quarries can split a 3/16” (5mm). The Glendyne quarry, in Quebec, Canada, which produces the North Country Unfading Black can split as thin as 3-4mm which is sold in Europe as La Canadienne and La Quebecoise.
A true 3/16” (5mm) slate weighs 650 pounds per square when installed with a 3” headlap. In some cases the decision to install a thinner natural slate may eliminate the need for structural modifications and will maintain the home’s resale value.
Some may question, will a 3/16” last as long as a ¼” or 3/8”? The answer is yes! Glendyne tests its slate every year, to ensure it passes the ASTM C406 (S1) in North America, EN12326-2 in the United Kingdom and ATGH768 in Belgium. Regardless of thickness, an S1 slate is tested for ASTM Flexure Testing of Slate (C120), Water Absorption of Slate (C121), Weather Resistance of Slate (C217) and Modulus of Rupture (C99) in order to pass the C406. When installed with a copper nail, this will ensure the slate stays in place for up to 100 years.
North Country Unfading Black slate has been a go to for many architects, home owners, universities and churches because of its quality, consistent thickness, availability and value. The 3/16” lightweight slate has been popular in Texas and California.
Standards 3/16” 650-800 lbs./square
Quarters ¼” – 3/8” 800-1200 lbs./square
Heavies 3/8” – ½” 1200-1800 lbs./square
Extra Heavies ½” – ¾” 1800-2500 lbs./square
North Country Slate has been a proud distributor of the North Country Unfading Black roofing slate for the past 20 years.