A roofing company tossing supplies after a job is complete.
Scrap metal is thrown in the trash instead of scrapped. Extra shingles, underlayment, sheet metal, and nails are thrown in the trash instead of saved for future jobs.
Trowing away nails, shingles, underlayment, sheet metal. All of those things can be used on future jobs.
Other wastes would include; excessive supervision. A working supervisor is better than a person standing around watching. This will will drive up overhead costs. Excessive work hours also leads to waste, longer work hours are actually less productive per hour, having a larger crew to reduce the length of the day will accomplish more work.
Other wastes include wasted manpower due to lack of proper tools or sufficient quantity of tools. If people are waiting for tools or the air compressor is not sufficient then the roofing will take longer.
Then there is wasted fuel cost. Some companies will bring multiple vehicles to a job, not due to bringing tools but due to not car pooling.