Producers A and B - Product 1

These products are unique in that they have the lowest density of the artificial shake or slate shingles that were offered to the industry because of the perlite (lightweight aggregate) incorporated in their formulations. Portland cement and expanded perlite are the principal ingredients. Minor additions include fibers from cardboard (thick paper), clay and tallow.

With water added, these materials are pressed into molds, dried, lightly coated for color, dried, packaged and sent to the field. Producer A started the production of shakes. The business was sold to Producer B, and a new product was announced. We compared the products manufactured by the two producers and found the products to be identical.

Our field investigations showed the top coating flakes off the shakes; the surfaces have a spider web of cracks, many extending through the body. The surfaces feel soft, powdery and eroded. Many shakes cup upward and support luxuriant growth of grass and weeds.

Laboratory data reveal these shakes have the lowest density of this group of manmade products, the highest water absorption (46 to 64 percent) and next to the lowest flexural strength (208 pounds per square inch [psi]). A 3.4-pound handleability index shows they are more brittle or friable than natural slate, which we have measured to have a minimum 8-pound index handleability.

Producer C - Products 2 and 3

Producer C provided two products to the market. Product 2 was shakelike with some corrugations or ridges down its face and a flat underside. Product 3 had a greater resemblance to tile and had reinforcing fins on its underside. Both had similar compositions: ground wood that had been previously treated to reduce soluble sugars mixed with Portland cement and water, pressed into molds, oven dried, sprayed with a surface coating, packaged and shipped.

During our field investigations, we found extensive surface erosion with many wood fibers exposed to the weather, frequent cupping of Product 2 and cracked shakes.

Product 3 had built-in gutters between the tiles that were often blocked by dirt and rooftop debris. These gutter dams caused water to drain over the edges of the gutters onto the underlying asphalt felt water-shedding membrane—in many cases eroding a path through the felts.

Laboratory tests showed these products to have a similar density (1.4 g/cm3) and flexural strength (617 psi), below the minimum saturated modulus of rupture (798 psi) listed in ASTM C1225, “Standard Specification for Fiber-Cement Roofing Shingles, Shakes, and Slates.”

The 4.2-pound handleability index shows the products are more friable than natural slate. Product 2 had a warp or cupping (see Photo) of 3⁄4 of an inch that is flattened by a modest 24-pound load on the front edge. Water absorption of 24 to 25 percent is consistent with many other fibercement shingles and shakes.