It is critical to keep a sharp eye on workmen.
Case in point. During hurricane Hugo, most of my shingles had blown off and FEMA gave me more than enough to have the job done.
Before the workmen arrived, I crawled up on the roof and examined the plywood. I found several pieces of plywood that needed to be replaced. When the workmen arrived I informed the foreman about the 3 sheets of plywood that needed to be replaced and he said he would do so. Sure enough, the workmen started to lay new tar paper and they rolled it right over the damaged 3 pieces of plywood. I called a HALT to the work and demanded that the job be done correctly. I made them remove the new tar paper and replace those 3 sheets of plywood. I watched every step.
So, you see, it pays to keep a sharp eye on workmen.