What does the allowance factor account for in material estimation?

The allowance factor plays a crucial role in material estimation, specifically accounting for variables that can affect the quantity of materials needed for a roofing project. When it comes to this context, over cutting and lapping are significant factors that must be considered.

During the installation process, materials often require cutting to fit properly, especially when working with various shapes, angles, and dimensions of a roof. This cutting can lead to waste, which is why the allowance factor accounts for that additional amount. Similarly, when materials are lapped—overlapped for waterproofing or for aesthetic purposes—this process can add to the material requirements. By factoring in over cutting and lapping, estimators ensure that sufficient material is ordered to avoid shortages during the project.

The other options, while relevant to construction projects, deal with separate aspects that do not directly relate to the specific material estimation process involved with roofing. Labor costs, design changes, and shipping fees pertain more to different considerations in project management and budgeting rather than the inherent material usage and wastage during installation.