A properly-installed roof that's in good condition is critical to the structural integrity of your flip. But if your roof needs work, in what instances should you patch it or replace it altogether? Consider these three reasons to replace your asphalt shingle roof. You Have Detached Sections of Shingles If you find shingles in your yard, or entire sections of shingles sliding from your roof, it's time for your roof to be replaced. This kind of damage indicates that the roof wasn’t installed using the proper techniques. When replacing your roof you should also verify that there is proper ventilation in the attic