Trapped water is easily prevented.

A slight separation

A slight separation between slates is all that is required to break or weaken capillary action, free trapped water and dramatically speed drying.

Testing shows that a 1.2 mm (< 1/16") gap lets slates dry 8X more quickly than unspaced slates, drying in minutes instead of hours.

Known for long life, slate can last even longer — if it is permitted to dry at an unimpeded, natural rate. Comprehensive cost is reduced. Energy is saved, as less is required to produce and deliver replacement roofs. And quarry life is extended.