House wrap, also known as a weather-resistive barrier (WRB), is a synthetic material installed over the exterior sheathing before the final siding is applied. Its primary function is to act as a secondary defense against moisture intrusion, preventing water that penetrates the siding from reaching the wall assembly. The wrap also serves as an air barrier, which helps reduce drafts and improves the home’s energy performance.
The Typical Lifespan
The expected lifespan of house wrap, when properly installed and protected by exterior cladding, is comparable to the life of the home itself. Under ideal conditions, a high-quality synthetic house wrap should last for 20 to 30 years or more. This longevity depends entirely on the wrap remaining shielded by the siding, which acts as the primary protective layer. The material is engineered to function as a permanent part of the wall system, provided it is not exposed to ultraviolet (UV) radiation.
The house wrap’s durability is linked to the maintenance of the exterior siding. If the siding is well-maintained and replaced when necessary, the house wrap beneath it is likely to remain intact and functional for decades. Its long-term performance relies on it being sealed within the wall cavity, protected from physical damage and UV light.
Factors Influencing Longevity
Exposure to ultraviolet (UV) radiation is the single most significant factor that shortens a house wrap’s lifespan. Synthetic wraps, typically made from polyolefin materials, begin to degrade when exposed to sunlight, leading to a loss of tensile strength and reduced water resistance. Manufacturers specify a maximum exposure time, often between 120 days (four months) and nine months, depending on the product’s UV inhibitors. Leaving the wrap exposed beyond this limit can compromise its ability to repel water and air.
The quality of the installation also heavily influences the wrap’s long-term effectiveness. Improperly lapped seams, where the upper layer does not overlap the lower layer, can allow water to bypass the barrier and reach the sheathing. Tears, wrinkles, or insufficient taping of seams and penetrations create pathways for air and moisture infiltration, which accelerates the degradation of the wall assembly.
The type of material used also plays a role in durability. Modern synthetic wraps, such as spun-bonded polyolefin, are generally more durable and water-resistant than traditional asphalt-saturated felt paper. Some advanced wraps incorporate UV stabilizers or are self-adhering, which eliminates the need for mechanical fasteners and seals around nail penetrations. Climate conditions, such as extreme temperature fluctuations or constant wind-driven rain, can also stress the material and accelerate wear.
Signs of Failure and Replacement
Identifying a failing house wrap is challenging because it is concealed behind the exterior siding. Homeowners must look for indirect symptoms indicating moisture has breached the wall assembly. These signs include water stains on interior walls, peeling exterior paint, or the presence of mold and mildew growth inside the wall cavities. Rot in the sheathing or framing, often discovered during a renovation, is a definitive sign that the barrier has failed.
If the house wrap is visible during a renovation or siding replacement, physical signs of degradation include a chalky surface, discoloration, or the material becoming brittle and easily torn. Crumbling dust behind the siding is a clear indication of long-term failure, often due to excessive UV exposure before the siding was installed.
The most practical time to inspect and replace the house wrap is when the exterior siding is being removed for maintenance or replacement. If the siding is off, it is an opportune moment to upgrade the barrier to a modern, high-performance product. Replacing the house wrap ensures the new siding is installed over a fully functional moisture and air barrier, maximizing the life of the entire wall system.
Maximizing Durability
The most important step in maximizing house wrap durability is ensuring the exterior siding is installed promptly. The wrap must be covered within the manufacturer’s specified UV exposure limit, which is typically a window of four to nine months, to prevent photo-degradation. This immediate protection shields the synthetic material from the sun’s damaging UV rays, preserving its tensile strength and water-repellency.
Proper flashing around all penetrations, such as windows, doors, and utility lines, is also necessary for long-term performance. These areas are common failure points, and using specialized flashing tapes to seal the wrap to the window and door frames prevents water from migrating behind the barrier. The installation must follow the principle of shingling, where upper layers overlap lower layers, directing water downward and away from the structure.
Maintaining the exterior siding is the best way to protect the underlying house wrap from premature failure. Regular maintenance, such as repairing cracks or replacing damaged sections of siding, prevents bulk water from constantly saturating the wall assembly. Furthermore, incorporating a drainage plane, such as a rain screen system or a drainable house wrap, allows any incidental water that penetrates the siding to quickly drain away instead of sitting against the wrap.