Dictionary of Moisture Protection & Restoration

3. Wind / air currents

When wind is present in a rainstorm, envelopes or cladding become increasingly subject to water infiltration. Besides the water being directly driven into the cladding by the wind currents, sufficient air pressure can cause hydrostatic pressure on the façade and force the water upward and over the components. Again, proper flashings should be designed and used to prevent this phenomenon from causing water penetration into the structure.

The cleat will at the bottom prevents uplift of the system.

Flashing used to prevent water under pressure from entering.

The height of the flashing is determined by the expected maximum speed and wind pressure. All too often the height is not adequate because of aesthetic conflicts. This detail is too important to take a back seat to design consideration.

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