Mystic Grey

What to Consider When Planning a Slate Roof

When a homeowner is considering a natural slate roof, several important factors should be reviewed. Two of the most important ones are the quality of the roofing slate used on the new roof and the quality of the installation.

The quality of any roofing material is an important consideration for any roofing project. Natural slate is no exception to this rule. Many individuals may not know that natural slate roofing is available in three distinct levels of quality—S1, S2, and S3. As can be expected, the highest-quality slate provides the longest service life with regard to resistance to water absorption, having the highest break strength and the highest resistance to weathering. Slate quality is determined by a standardized set of tests that are defined by ASTM International (formally known as the American Society of Testing and Materials). These tests are performed by a third party, which is most often a certified testing laboratory that has been approved to perform the tests. The highest and best grade of slate available today is Grade S1 slate. S1 slates can be found in upstate New York, Vermont, Canada, and Virginia, as well as through some overseas sources. To achieve an S1 rating, the slate must pass all the tests. If a slate supplier cannot provide you with Grade S1 slate, you may want to consider another slate supplier. At GAF, we are proud to offer only Grade S1 slate on all colors offered in our TruSlate® Genuine Slate collections. Our slate is sourced from the New York & Vermont quarries, as well as from Canada and overseas quarries.

Another important consideration is having the experience to do the job correctly. Using the best roofing materials available does not ensure that the slate roof will perform as expected.  Having the installation completed by an experienced slate installer is absolutely critical. Many contractors are part of GAF’s Certified Contractor Program, which helps homeowners take the guesswork out of choosing the right contractor. In order to become a certified TruSlate® installer (i.e., a Certified SlateCrafter™ Specialist), a contractor must pass practical and classroom testing. Thereafter, the contractor’s status is reviewed on a regular basis to determine if their SlateCrafter™ certification will remain in effect. If slate roofs are popular in your area, it may be worth it to become a Certified SlateCrafter™ Specialist. In the past, it took years to become a qualified slate installer.  But with the unique TruSlate system, any competent roofing contractor can learn how to become a fully qualified installer in days, not years. This will open up a whole new market for your business, including commercial jobs that use slate, like churches, office buildings, etc.

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  1. Black Diamond Slate

    Great post. So true that quality roofing slate should be used on a new roof along with a quality slate roofing installer; not everyone knows how to install slate tile. Thank you for sharing this blog post about slate – please keep it up!!


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