If your roof isn’t very old and you spot a few loose or damaged shingles, you may be able to just replace them. But for broader or more extensive damage, it may be time for a new roof. The key is a regular roof inspection so you know what’s going on up there.

Attic leaks

Check your attic after severe weather. A leak could mean some shingles are damaged, the underlayment — a protective barrier between your shingles and the plywood of your roof — has failed, or flashing — the material that seals joints on your roof — has deteriorated.

Blistering or peeling paint

Poor ventilation may cause moisture to get trapped in your house, which may cause exterior paint to peel and blister.

Ceiling and wall stains

Leaks from outside the house or moisture trapped inside it can cause stains and possibly mold or mildew.

Sheathing decay

Another issue with poor ventilation and moisture in your layers of roofing materials is the decay of sheathing — also called decking — which is the layer of plywood that forms the foundation of your roof. If you notice a sagging ceiling, broken gutters, leaks or missing patches of shingles, your sheathing may be damaged.

Shingle damage

When shingles reach the end of their useful life, you may notice they fall off or become cracked, brittle or curled, which means it may be time for a new roof.

Dark streaks

It may look like dirt, but dark stains on your shingles may be moss, lichen, or blue-green algae.