A.Jeff Keisling, vice president of research and development for Azek, responds: While Azek isn't rated for structural applications, it does have a limited amount of strength. For example, 1/2-inch-thick Azek has a compressive strength of about 1,000 pounds per square inch, which is much less than the compressive strength of wood.

If you're confident that you've accurately calculated the actual loads and the surface area of your supporting columns, and that you've detailed the bearing surfaces so that there is full contact across the total surface area (rather than point loading), it may be safe to use a cellular PVC product like Azek this way. But it would be best if structural members bore directly on one another, with the trim material cut to fit around the structural bearing points.

For situations where larger laminated support beams, columns, and joists need to be covered, Azek now offers trim boards as wide as 16 inches, in addition to a full line of sheet goods.