The use of lightweight concrete as a roof decking and insulation system has expanded in the past five years. Increased usage can be attributed to the recent industry-wide insulation shortages and delamination deficiencies. The increase can also be attributed to the economic and environmental advantages that lightweight insulating concrete (LWIC) provides in roof assemblies. The increased use in specific regions of the country has spawned new technology to meet the demands of the market from the economic and environmental standpoints. Advances in pumping equipment and mixing ratios have provided materials that are consistent in compressive strength and density.