Slate Technical Specifications
Thickness, weight and grading determine what a slate roof can do and what your structure needs to carry. These are the numbers, without the marketing.
What are the thickness options for roofing slate?
Roofing slate thickness varies, with standard options typically ranging from 1/4" to 3/8". Some slates are available in 3/16"-1/4" or up to 1"-1 1/4" thickness. The availability of different thicknesses depends on the specific slate and quarry.
How much does slate weigh?
The weight of slate varies depending on its size and thickness. While traditional slate is heavier than some roofing materials, our SLATE2 system offers genuine slate at under 6 lbs. per square foot for 1/4"-3/8" thick slate and under 9 lbs. per square foot for 3/8"-1/2" thick slate, significantly reducing structural considerations. Our technical specifications provide detailed weight information for each product.
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Is slate too heavy for my home?
Traditional slate requires structural capacity. SLATE2 is 100% natural slate at under 6 lbs per square foot for standard applications, which usually eliminates the need for structural reinforcement and opens genuine slate to homes and re-roofs that could not carry the traditional weight.​
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What are ASTM standards for slate roofing?
Slate roofing is rigorously graded according to ASTM C406 standards. S1 is the highest grade, indicating the highest quality slate with the longest projected lifespan, which is the standard we uphold for our premium products.
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How much of the slate shows?
The portion of the slate that is exposed to the weather is called the "exposure." This is determined by the length of the slate tile and the headlap. For instance, an 18-inch slate with a 3-inch headlap would have a 7.5-inch exposure. The exposure contributes significantly to the visual pattern and aesthetic of the installed slate roof.​​
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What makes slate brown?
The natural color of slate, including shades of brown, is determined by its specific mineral composition and the geological conditions under which it formed. Iron oxides and other minerals within the clay or volcanic ash can impart unique brown, tan, or even multi-colored hues to the slate. The characteristics of weathering are specific to Vermont slates and not Spanish or Brazilian slates, which are unfading. Vermont semi-weathering and weathering slates will yield, over time, a variety of rich earth tones. When extracted from the quarry they are monochromatic. For semi-weathering slates, about 10-25% will gradually change to soft tones of buffs and tans after exposure to the weather. The degree of change for weathering slates can range from less than 30% to more than 90%. For either type of slate this process begins 1-2 years after exposure to the climate. This weathering continues to some degree throughout the life of the slate but does not diminish the longevity of the material. The weathering process is unpredictable and not guaranteed. These slates have been quarried since the mid-19th century.​​
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