Dictionary of Moisture Protection & Restoration

2. Surface tension. Water adheres to the surface of an opening and travels inward along it.

3. Capillary action. Water travels inward because its adhesion to the walls of an opening is stronger than the cohesive forces between the liquid molecules. This occurs in very porous substrates.

4. Wind / air currents. The wind currents can create sufficient air pressure to force the water upward and over the components.

5. Hydrostatic pressure. Pressure applied to the building envelope materials by various heights of water at rest.

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