You can let the worker to mount solar panels on a purpose-built aluminum rail system that is fastened about every four feet by penetrations into roof rafters. On a standing seam metal roof, these attachments are made directly to the standing seams, with no roof penetrations. On asphalt roofs, each mount is sealed with a 50-year Tripolymer sealant to prevent any leaks. We guarantee all roof work will be free from leaks. As for the weight of the array, it is less than 5 pounds per square foot, so a typically framed roof is more than adequate to carry the weight.