Short Answer
House wrap is commonly used as a weather-resistive barrier in wall assemblies. It is part of a water-management strategy and should be installed according to its specific requirements.
Detailed Explanation
House wrap is a thin, breathable membrane installed over the wall sheathing and beneath the siding. Its primary function is to act as a weather-resistive barrier — it allows water vapor to pass through (letting the wall dry out) while blocking liquid water from entering. It also helps reduce air infiltration through the wall assembly. Proper installation is critical: house wrap must be properly lapped (like shingles, so water sheds downward), properly flashed at window and door openings, and properly sealed at penetrations. If house wrap is installed improperly — with reverse laps, unsealed penetrations, or missing flashing integration — it can actually trap water rather than shedding it.
Why It Matters
House wrap is the secondary water-management layer behind siding. Its proper installation is as important as the siding itself for preventing water intrusion.