Slate roofs have been utilized in Europe for nearly 1000 years. They adorn most of Europe’s historical buildings and have helped define many European architectural styles. In fact, slate is well known to outlast the fasteners holding it and the roofs are taken up and re-fixed using new nails, ensuring that the building remains watertight while keeping its historical aesthetics. Today, an ASTM S1 slate roof is rated to last at least 75 years and Greenstone Slate® has a 100 year warranty. It is a lifetime investment that adds to the value of a property for its aesthetics, durability and anticipated low maintenance.

Not all slate is the same. Fortunately, there are engineering standards that create clear performance ratings for slate sourced worldwide. Greenstone is located in the Slate Valley of Vermont—known for its top quality slate. Vermont slate is the basis for the Greenstone roofing slate’s S1 (best) rating by ASTM International, an independent organization that sets standards for building materials. S1 roofing slate is rated to last 75 years. Greenstone provides a 100-year warranty for its slate. Slate’s durability alone plays a key role in enhancing your property.

From cold to heat, dry to wet, it does not curl, shrink or deform. Slate’s physical stability protects your home better than any man-made material.

Greenstone Vermont slates absorb less than .0025% of their weight when submerged for 72 hours, giving them the prestigious ASTM S1 classification, the highest rating available.

Vermont S1 rated slates are exceedingly strong at a mere 1/4″ inch thickness. At 3/8″ thickness or more, Vermont slates have received a Class 4 hail rating for Architectural Grade as confirmed in independent laboratory testing. For Standard Grade Rough Texture (between 1/4” to 5/16” thick) a Class 3 hail rating was achieved. This can benefit homeowners by lowering their insurance premiums and/or in some cases assuring insurance coverage (check with your insurance agent about slate roof coverage). The increased material cost of better grade slates is often offset by the insurance benefits. As well, thicker slates have an even the longer life expectancy.

Slate is natural stone so it simply does not burn. It exceeds all fire resistance standards. Some roofing materials that might not technically burn are still affected by the intense heat of a house fire. It is because they can contain a percentage of water as the result of absorption. As the water inside is heated, it expands, causing the roofing tiles to crack or even explode! A Greenstone S-1 slate roof, with virtually no water absorption, is automatically deemed a Class A fire proof roof in some locales.

Solar panels are usually mounted on an elevated metal framework and many agree that the installation interrupts the roofline and is inconsistent with the aesthetics of the building design—especially when installed on a slate roof.

Imagine solar panels integrated flush into an elegant slate roof and you’ve just imagined a slate roof installed using SlateTec™ and Certainteed’s Solstice® high-performance solar panels.

Slate’s longevity does more than save the cost of installing five or more replacement roofs. The reduction of construction waste is an important goal for the improvement of the environment and should be a factor when considering a sustainable roof. A slate roof better protects the building reducing potential cost of repair from water leaks and storm damage which also contributes to slate’s sustainability.