The Next Generation

There are a number of artificial slate and shake products available that are manufactured using rubber and plastic materials. Products made with EPDM certainly have a sister product with a long-term performance history in single-ply roofing.

The products are offered in styles to imitate slate in all the colors found in natural slate, as well as all shapes and sizes of imitation wood shakes. Some of these products have been on the market for more than 10 years and reportedly have been installed throughout the U.S. All the products we reviewed are offered with 25- to 50- year warranties, a period of time that should be considered long-term relative to the products’ track records.

We have little experience with the performance of these products at this time. We suspect the reason is, in part, because we haven’t been called to look into any project failures. It is not the nature of our engineering consulting business to be hired to look at successful installations that continue to function as intended.

The installations we have seen are attractive and appear to achieve the desired look of slate or shake roofing. We hope these products will continue to perform and maintain their appearances for a long time.

However, based on our experiences in the roofing industry, we offer the following advice if you use any product that does not have a history of successful use that matches the intended life of a roof system:

• There is no test or group of tests that can predict a roof system’s service life except the test of time.
• Installing a roof system that has less of a track record than its expected life is an experiment; this is acceptable as long as its owner is a willing participant.
• There are different interpretations of “performance” and “failure.” Is the product that was selected to provide a desired appearance a failure when it quickly loses its applied finish even though it doesn’t leak?
• Try to get a clear, upfront understanding of the owner’s expectations. Explain the remedies available for poor performance.
• Investigate other installations, and talk to the owners regarding their experiences.
• Follow manufacturers’ installation instructions.
• Warranties are legal documents that are used as sales tools. Warranties provide more protection for roofing manufacturers than they provide purchasers. Do not rely on a warranty to ensure performance.

Author’s note: We wish to acknowledge the influence of our late friend, colleague and mentor Carl G. Cash on the preparation of this article. Carl was instrumental in many of the investigations and much of the research that went into the evolution of the information and the conclusions presented here. Much of this was written with Carl’s voice in the back of our heads, continuing to guide us in the present as he did when he was with us.