Patent ID: 7617647

Claim:
A plank adapted to support tile comprising an elongated fiber-reinforced thermoset composite pultruded member having a thin base and a plurality of solid ridges extended up from said base; said base having a height of about 1/32 inch to about ¼ inch; said plank having a height measured form said base to a top surface of said solid ridges of 13/32 inch to about ¾ inch; first and second sides adapted to interfit with adjacent planks; wherein said ridges have a base portion and a distal portion wherein said base portion in narrower than said distal portion forming areas between adjacent ridges having generally trapezoidal cross sectional configurations; wherein said plank is capable of being fastened directly to floor joists and support a layer of tile adhered to said plank and provide a tile structure with a break strength of at least about 7,019 N.