35 5 Supply Better What if all the materials on a construction site were used? The last step, from manufacturer to building, offers significant possibilities for reducing material use. How materials are handled on- site and how they reach the site could both be improved. Most construction materials are relatively inexpensive compared to the cost of transportation. Contractors in many different places use large overage estimates to ensure that the basic materials needed are readily available on-site. When extra material is not used, it often becomes waste. Improper storage, damage during transportation, cutting to size, and mixing materials like plaster on-site all contribute to construction-site waste, which is often estimated to be around 10 percent. For some projects, this figure is perhaps far higher: recent studies of Brazilian construction sites show that median wastage rates for cement and aggregates can be as high as 45 percent. 1 More accurate estimating practices and training to improve on- site handling of materials could significantly reduce the amount of waste created by delivery and construction. Reclaiming and reusing offcuts and excess would further improve material use on-site. 1 United Nations Environment Programme, Eco-efficient Cements: Potential Economically Viable Solutions for a Low-CO 2 Cement-Based Materials Industry (Paris: UNEP, 2016), 24.