PUR RIM vs. Wood in Building Products

After nearly a decade of testing, roofing shakes of RIM polyurethane microcellular rigid foam are making a commercial push to compete with traditional cedar shakes. Called Durathon, the patented PUR hybrid material is said to be more durable and longer lasting than wood while offering similar aesthetics. Durathon is the brainchild of Endur-All Technologies, Inc. (ETI), a Denver company started in 1996 to use new materials for innovative building products. Now that its molded PUR technology has gained some credibility in the cautious building-products industry, ETI aims to explore other wood-replacement applications.

According to ETI chairman and CEO Terry Lawson, it was the insurance industry that spurred the development of Durathon Ce-Dur Shake. Weary of millions of dollars of roof losses due to hail and wind in the states of Colorado, Wyoming, Nebraska, and Kansas, State Farm Insurance began to promote the development of a range of new roofing materials through a rigorous new performance test and a standard for impact resistance.

ETI’s Durathon is composed primarily of polyurethane from its strategic partner, Pittsburgh-based Bayer MaterialScience. Another important (and patented) ingredient is PVC resin powder—both a dispersion grade and a blending grade. Says Lawson, “PVC is a significant contributor to the functional characteristics of the product. It serves as seed sites for formation of the polyurethane foam cells.”

The patent also involves the use of a “structural” filler—in this case, recycled glass. It adds properties useful for roofing and serves as a significant cost reducer for the total system, notes Lawson.

ETI molds Ce-Dur shakes in tools created from real cedar shakes to produce a realistic replica. Like wood shakes, they are offered in 5-, 7-, and 12-in. widths. The tapered, 23 1/4-in.-long shakes taper from 5/8-in. or 1-in. thickness down to 1/8 in.

 

A cautious industry

The first field-test installation was made in 1997, and a total of 19 homes have Ce-Dur roofs in Rocky Mountain and Great Plains states, which have the most extreme temperature swings. “We’ve taken the risk out of the material with our extensive testing,” says Lawson. He says past failures with other replicas of cedar shakes have made the construction market wary of new materials. “The roofing industry insists on real-world proof before they will accept a new and innovative product. As we now begin to ramp up for full commercialization, we find ourselves with over $3 million in backlogged orders.”

Ce-Dur shakes reportedly provide Class A fire resistance, extreme impact/hail resistance and superior uv stability. They also have 110-mph wind certification and are impervious to freeze/thaw effects. Field tests have shown them to outperform wood shakes in resistance to fire, wind, hail, and freeze/thaw cycles, and also to have improved “walkability” and lighter weight when wet.

Besides looking like wood shakes, Ce-Dur shakes are installed in the same manner—hand nailing, power nailing, or power stapling. The cost of Ce-Dur shakes is currently about $5 to $10 per square (100 sq ft) higher than cedar wood shakes, while the installation cost is the same. Says Lawson, “There is a beginning of a trend that suggests we will be below the cost of wood, since the price of quality wood shake is on the increase.” The installed cost of Ce-Dur shakes also compares very favorably with concrete, metal, and other new material products, like trilaminate. “At this point, we are probably $20 per square higher than trilaminate, but our performance is typically superior in life expectancy, impact resistance, and moisture absorption,” Lawson claims.

Meanwhile, ETI is working with Bayer to broaden the scope of its technology. Says Lawson, “We are exploring licensing opportunities outside of residential roofing. With slight changes in formulation, anything in a building that looks like wood has potential, including window frames, shutters, and decking.”