Roofing Glossary

Thermal Splitting

Thermal splitting is the cracking of shingles caused by years of expansion and contraction as the roof heats and cools. As asphalt ages and loses flexibility, it can no longer absorb the daily movement — so it splits, usually in straight vertical cracks through the shingle.

Splits typically run vertically through the exposed portion of the shingle, following the path of maximum stress. They are most common on older organic-mat shingles and on roofs with extreme temperature swings — dark roofs on poorly ventilated attics see the widest daily temperature range.

A split shingle is a direct leak path: water runs into the crack and under the shingle. Unlike surface wear, splitting is structural failure of the individual shingle.

Why It Matters

Thermal splits are not cosmetic — each one is an open channel for water. Widespread splitting means the shingle stock is exhausted and patching individual splits is futile.

What to Watch For

• Straight vertical cracks through shingle tabs
• Splits concentrated on the hottest, sunniest slopes
• Cracks that extend through the full shingle thickness

Questions about your own roof? Request a free estimate or call Nucci Brothers Roofing at (301) 458-1003.