Why frost is the main risk

Question

Accepted Answer

Water expands by around nine percent when it freezes. On coping stones, the risk is not the freezing temperature itself but what happens when water that has been absorbed into the stone or its mortar joints freezes and then thaws repeatedly. Each cycle forces the material apart fractionally. Over multiple winters, this produces spalling (where the surface of the stone flakes away), cracked mortar joints and, eventually, loose or shifted stones.

How to Protect Coping Stones During Winter and Frost