5/4"x6" treated, cedar, redwood and composite decking do not have the same degree of span strength that a 2"x6" treated or cedar board does. 5/4"x6" decking boards are thinner and typically have rounded edges, which decreases the overall strength of the board. For this reason, a narrower span of 16 inches on center is required between support boards. Thus the great number of blocks and support boards for the project.

Always check with your composite board manufacturer for the span support required for the board type you'll be using. Some composite boards can only span 12 inches on center, while some can span 20 inches. These spans are very uncommon.