Before installing roll roofing, what should you do first?

Snapping a chalk line 18-3/4" above the eaves is an essential first step before installing roll roofing because it provides a clear guide for laying the roofing material evenly and accurately. This measurement helps ensure that the roofing is applied at the right angle and position, which is crucial for proper water drainage and preventing leaks. Having a reference line promotes a neat and professional appearance, as well as helping to avoid misalignment during installation.

The other options do not address critical preparatory steps needed for a successful roofing installation. Installing the roof covering immediately would likely lead to complications or mistakes, as the roofer would not have a guide for alignment. Laying all sheets at once could result in uneven installation and is typically not practical or effective without proper planning and measurement. Waiting for dry weather is important for ensuring proper adhesion and application, but this should come after establishing the necessary guidelines and preparing the work area. Thus, snapping the chalk line is the logical and foundational step that sets the stage for effective roofing installation.