waterimpermeable

Water-impermeable describes materials and structures that resist water penetration under defined conditions. It denotes a higher level of protection than simple water resistance and is related to, but not identical with, waterproof or watertight. The exact meaning depends on test conditions such as duration, water pressure, and temperature, and performance is never guaranteed under all possible circumstances.

Measurement and standards: Impermeability is demonstrated through standardized tests that specify water pressure (hydrostatic head), duration, and allowable defects. In textiles, hydrostatic head tests determine the maximum water pressure a fabric can withstand. Building envelopes use water intrusion tests, while packaging and electronics may rely on moisture-barrier tests. Rating systems such as IP codes and regional standards quantify impermeability for particular environments.

Applications: Waterproof membranes (EPDM, PVC, bituminous sheets), coatings and laminates are used in roofs, basements, and walls to create water-impermeable layers. Water-impermeable fabrics use coatings or laminates to keep out rain. Moisture-barrier packaging uses metalized films, foil, or multilayer plastics to protect contents from water vapor.

Limitations: No material is perfectly impermeable. Integrity depends on thickness, installation, and condition. Damage, aging, punctures, or high pressure can compromise impermeability, and extreme temperatures or prolonged exposure may degrade performance. Designers specify tests and maintain warranties based on real-world use.

See also: waterproof, water resistance, moisture barrier, vapor barrier, hydrostatic head, IP rating.