House Wrap Importance
House wrap is defined as all synthetic materials replacing sheathing paper. House wraps are a lightweight material and wider than asphalt designs, allowing a faster installation procedure by builders and contractors. This material forms a weather-resistant barrier minimizing moisture intrusion and improving a building's energy efficiency. This type of material will also permit the transfer of water vapor to the outside of the protected structure. This is an important characteristic of a house wrap, because if water vapor is allowed to build up within stud or walls, moisture and mold will likely decrease and reduce the insulation characteristic or the R-value. All houses that are framed with lumber need protection. Most newer house wrap materials do not perform well against nails or staples like asphalt products.Participate on our House Wrap Poll Here.
House Wrap Purpose
The purpose of using house wrap is to prevent the entry of moisture, or rain into the wall cavity. Some sidings are now available that can perform this function, eliminating the need for sheathing paper. House wraps also provide a continuous membrane protection covering all cracks, gaps, and orifices between the exterior sheathing and the rigid foam insulation.
In certain instances house wrap can also act as air barriers if it is sealed at every seam. House wrap can be resistant to abuse by construction workers because sometimes is left exposed for some time awaiting siding installation to be completed. A good house wrap material must provide waterproof protection and have a high moisture vapor transmission rate to be considered effective. Some newer house wrap designs must be handled carefully to avoid rip or tear from the material.
House wrap is intended to be installed over the sheathing and behind the siding, no matter what siding you are using: brick, vinyl, concrete or any other material used. The house wrap will stop or reduce moisture inside the house and reduce the water condensation or mold problems getting into the studs or wall cavity.
House Wrap Types
Asphalt-impregnated paper or fiberglass (also known as Asphalt Saturated Felt, heavier and slower installation)
Micro-perforated, cross-lapped films
Films laminated to spunbond nonwovens
Films laminated or coated to polypropylene wovens
Supercalendered, wetlaid polyethylene fibril non-woven (most commonly used)
House Wrap Benefits
Most house wrap exceed code requirements for air and water barriers.
Provide U.V. Protection.
Available as translucent material for easier installation of the wrap itself and the exterior siding.
Save homeowner money on heating and cooling costs.
Some house wrap material offers tear resistance.
Reduce air infiltration.
Excellent moisture control on humid climates.
Allows vapor to flow out of the building.
House Wrap Disadvantages
If house wrap is not installed properly, it will cause more damage than benefits.
It is not a vapor retarder, and should not be treated as one.
Improper lapping of house wrap will cause mold and moisture problems.
If exposed during long periods of time, wind and construction debris can damage the house wrap surface.
Abuse or rough handling by employees can cause serious damage to the house wrap.
Gaps or seams not sealed effectively, will allow water to penetrate building's interior.
House Wrap InstallationTips
Follow these simple tips when installing house wrap:
All seams must be properly sealed with a special tape provided by the house wrap manufacturer.
Start from the bottom, and overlap the lower ones.
Install house wrap before doors and windows.
Wrap the fabric around the edges of windows and doors to the inside of the frame.
If possible install house wrap before the second top wall plate is installed.
Install the house wrap between the double top wall plate.
Avoid chemicals to be in contact with the fabric as they will adversely affect the house wrap’s water resistance.
Extend the house wrap over the footing top at least 2 inches.
It is recommended to install a drainage provision at the bottom of the external siding material.
Use specific stapling nails or nails designed to hold down house wrap material. Nails should be at least 1 inch ling and spaced 12 to 18 inches on-center
Horizontal joints should be lapped 6 inches minimum
Vertical joints should be lapped 6 inches minimum and 12 inches maximum, depending on the severity of the area's weather conditions.
Lap house wrap over the entire top of any step-flashed areas.
When porous siding is being installed, it is recommended to install a protective rain-screen to control moisture movement.