This document provides information about roofing materials and their installation. It lists various types of clay, concrete, and asbestos-free cement roof tiles. It also lists different types of corrugated steel roof sheets specifying their widths, side laps, and wastage rates. Formulas are provided to calculate the percentage of laps and wastage for standard sheeting. Finally, it outlines the labor output hours required to install asbestos-free cement and steel roof sheets based on the maximum sheet length using one roofer and one unskilled laborer.