A hydrophobic material or non porous material (such as glass, plastic, or metal) or gap between parallel layers of material (often less than ¹/₁₆” or 1.5 mm) sufficient to stop capillary action.

Related terms: Capillary Action, Hydrophobic

Related resource: BSI-011: Capillarity—Small Sacrifices, BSI-041: Rubble Foundations