What are the signs of a bad roof?

When your roof gets old or starts to get bad, you may experience a couple of things happening to your roof. 

First, there may be several loose or missing shingles, you may also notice that your roof is sagging. Another thing you may observe is water spots, algae, moss growth, or even if your shingles are curling, dry, blistering, or cracking. You may even spot exposed or loose nail heads. All of these things can occur with weathering or simply just age. It's best to act immediately and call a professional.