Shingle wear will almost always be greater on a south-facing roof because that side gets the most sun. If shingle ends are cupping and splitting, plan to reroof soon.
Mossy shingles or shakes are common in wet climates and on shady roof sections. Although moss-covered shingles can be relatively sound, the condition will induce rot because moss retains water.
If the house is in a fire-risk area, insurers may refuse to give a policy on a wood-shingle or wood-shake roof. In this case, replace it with noncombustible roofing.
Do not attempt to walk on slate roofs. Even when dry, they’re slippery. They’re also brittle and so break easily.
Off-color areas may indicate replacement shingles for those that suffered damage from a tree branch. Later, when you are in the attic, check for water stains on supporting lumber.
If you see rust-colored streaks or cockeyed slates, the installer may have used nails that weren’t galvanized, which by now have rusted through. Although it’s possible to remove and renail slate, the job requires a costly specialist. However, if many nails have rusted through, the roof is dangerous, and the slate should be removed.
Stay off tile roofs. Even when the roof slope isn’t steep, your weight could damage the tiles.
Inspect them from an extension ladder and with binoculars.
Look for odd-colored tiles from earlier repairs. Obviously cracked or broken tiles can be replaced, but the job is costly. In the attic, check for water stains.
Look closely at the ridge. Sagging ridge and rafters suggest too much weight on the framing. It’s a big expense to remove the tile, bolster or replace sagging rafters, replace sheathing, and then replace tiles.
Stay off metal roofs. They are slippery, whether wet or dry.
Even though a rusty roof may not look great, it could be watertight with a lot of years left. Roofs with superficial rust can be sanded and repainted. In the attic, check for evidence of leaks.
Note: Roofing panels should be nailed at the high point of metal folds. If you see many nails in the roofing channels themselves—where the water runs—the installation was inept, and you’ll need a new roof.
