Thermal shock is the expansion and contraction of roofing materials due to temperature fluctuations. It affects all kinds of roofs, although to different degrees. Roof thermal shock is one of the reasons your roof will age and need to be replaced one day, even if you maintain it well. You know your roof is experiencing thermal shock-related damage if it is exhibiting:
Cracking of Shingles
The asphalt mix, the main material used in the manufacture of asphalt shingles, is both stiff and water permeable. Therefore, manufacturers add chemicals known as volatiles that give the shingles a flexible and waterproofing nature. This is why the shingles aren't usually affected by temperature fluctuations; the flexibility allows them to expand and contract without permanent damage.
Unfortunately, these volatiles do not stay in the shingles forever; they evaporate in the atmosphere due to the action of weather elements on the shingles. Therefore, old shingles are likely to be stiffer than relatively newer ones. Such shingles expand and develop cracks on their surfaces when heated.
Buckling of Shingles
Just like other solids, individual shingles expand when heated. Buckling occurs when a line of shingles are heated and expand at the same time. This creates a problem because there is no room, which each shingle piece needs, for the expansion. The result is that the shingles push against each other, and the weaker ones get pushed up. This is why you may notice buckling shingles on some parts of the roof, but not all.
Loosening of Flashing
A good roof must be watertight. This is achieved by the use of flashing to seal the small gaps that exist between adjacent roofing materials. However, the flashing are also subject to thermal expansion and contraction. When this happens, gaps may open up in the sections of the roof that the flashing were supposed to seal, and moisture may start seeping into the roof structures.
Loosening of Fasteners
Fasteners are used to hold roofing materials securely in place. Obviously, this only works if the fasteners are immobile, which means they should fit tightly in their holes. This is usually the case when a new roof is installed. However, the temperature-occasioned expansion and contraction of the roof materials also affect the fasteners and their holes. After several cycles of expansions and contractions, the holes widen and loosen the fasteners.
There are several ways of reducing roof thermal shock. For example, you can have the roof coated with a reflective coating so that most of the heat is reflected away rather than absorbed by the roof materials. Talk to your roofing contractor about further maintenance practices to mitigate the effects of thermal shock on your roof.