Our front porch roof is a black material over galvanized steel. We have not had leaks but the steel is showing through and we need to cover it. It is about 25 ' by 14'. Two proposals from roofers have been to scrape and cover with some kind of gunk ($525) or cover with shingles ($1150). I could scrape and put some gunk on myself. What is the covering that is commonly used? I am worried that moving my 240 pounds around up there around could be a problem.