Producer D - Product 4

Producer D manufactured its products outside the U.S., and details of the manufacturing process are not known. These products are characterized by a strong—almost baked—enamel top coating. At one time, we considered Producer D the only one with a good performance record. Then, we began getting reports of cupping and top coating delamination.

Product 4 was reported to us to be reinforced with polymeric fiber reinforcement. The main problem with this product was color instability and curling, not extensive product breakage. Producer D has discontinued distribution in the U.S.

Producer E - Product 5

Producer E manufactured a cellulosecement product using a cylinder machine similar to the equipment used to make asbestos-cement sheets and shingles where the thickness was made of relatively thin sheets laminated together. Product 5 curled and became embrittled—probably because of carbonation of the free alkalis present—and frequently delaminated after weathering (see Photo 2). Walking on the roof broke the shakes (see Photo 3).

The 4.2-pound handleability index illustrates the products are more friable than natural slate. The 31 percent water absorption is much too high for a weather-durable product. Frequent wetting and drying in tropical environments caused the product to soften to the point that it could easily be broken by hand.

Producer F - Product 6

Producer F manufactured shakes made from Portland cement and ground wood with various additives, including fly ash, aluminum hydrate, aluminum sulfate and water. The mixture was pressed into molds, dried, lightly painted and shipped after curing.

The principal negative field observation is a constant tendency for the bottom edges of these shakes to cup upward. Many broken shakes were recorded. Any rooftop traffic caused the shakes to crack—often near the fasteners—where the crack is covered by the higher row of shakes.

The shakes’ flexural strength at 1,000 psi is the second highest of the shakes tested. The water absorption is 22 percent. The handleability index is 1.9 pounds—the second lowest in this group. The distance between the shakes’ bottom of the front edge and a flat reference table averaged 0.3 of an inch. A modest 44 pounds cracked the shakes and pressed them flat. These cupping and fracturing tendencies make maintaining a roof system with these products difficult if not impossible.

Producer G - Product 7

Product 7 is composed of about 35 percent wood fiber and about 65 percent hydrated cement. The shakes’ top surfaces are quite porous, and many shingle samples were cracked.

The average water absorption was 35 to 51 percent of the shingles’ dry weight. We found weathered surfaces absorbed water up to 16 times faster than unexposed surfaces. Wetting and drying of the fibers causes cycles of the fibers swelling and shrinking. In addition, soluble alkali salts migrated into the fibers and were converted to calcium carbonate—a well-known process of carbonation that embrittles shingles.