2018 Composite Decking Prices | Cost of Composite Decking.10 Oct 2017 . For solid polyvinyl chloride (PVC)-based decking, the average cost per square foot is $9.48, though buying this material in hollow slats can reduce the cost to around $7.50 per square foot. Overall . Despite being made of plastic, composite can warp or scratch and is thus, not indestructible. However.