How Weather Can Affect Your Roof

Weather does not damage roofs. It finds weaknesses

A sound roof shrugs off decades of everything the sky offers. The same roof with one lifted shingle or one badly flashed chimney will fail in a single season, because weather is relentless rather than powerful.

Understanding which conditions attack which parts of the roof tells you where to look after each kind of weather, which is far more useful than a general instruction to keep an eye on things.

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Sun is the slowest and the most certain

UV is what ends most asphalt roofs, and it does it quietly over twenty years by drying out the mat and loosening the granules that protect it. South and west-facing slopes always age first, which is why a roof can look fine from the street and be finished on the other side.

Heat compounds it. A poorly ventilated attic can run far hotter than the outside air, and that heat cooks the shingle from below at the same time the sun works on it from above.

What to check after each kind of weather

Different conditions leave different fingerprints, and knowing them saves a lot of pointless worrying.

• After wind: ridges, hips and windward edges for lifted or missing tabs
• After hail: gutters and soft metals — bruises rarely show from the ground
• After heavy rain: ceilings, upstairs corners and the attic on a bright day
• After snow: the eaves, for ice building where the rest of the roof is clear

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Wind damage starts at the edges

Wind does not lift a roof from the middle. It gets under an edge — a ridge cap, a rake, a tab that never sealed properly in a cold installation — and works from there. That is why perimeter detailing matters far more than the wind rating printed on the packet.

A shingle rated for 130 mph is rated for that only if it sealed. Installed on a cold day and never warmed through, it is rated for considerably less.

After any serious gale, look along the ridge line from the garden. A single displaced cap is a cheap morning’s work and an expensive winter if it is left.

Freeze and thaw is the quiet destroyer

Water that gets into a hairline crack expands when it freezes and makes the crack larger, then does it again the next night. Over a winter that turns a cosmetic flaw in mortar or flashing into a genuine entry point.

It is also why autumn is the right time for repairs. The same fix costs the same money in October and December, but only one of them happens before the freezing starts.