House wrap is a critical component of any high-performance building envelope. When installed correctly, it helps manage moisture, improve energy efficiency, and prevent air leaks that can compromise the structural integrity of a home. However, achieving an optimal installation requires attention to detail, adherence to best practices, and an understanding of the materials involved. This article outlines the key techniques and considerations for installing house wrap effectively, drawing from expert advice and installation guidelines provided by authoritative sources.
Understanding the Role of House Wrap
House wrap functions as a weather-resistant barrier (WRB) between the exterior sheathing and the cladding. Its primary purpose is to allow moisture vapor to escape while preventing liquid water from entering the wall cavity. This dual functionality makes it essential in protecting the home from internal condensation and external water intrusion. The effectiveness of house wrap is contingent on proper installation, which includes selecting the right material, preparing the wall assembly, and sealing all seams and penetrations.
Choosing the Right House Wrap Material
Selecting the appropriate house wrap begins with understanding the local climate and the type of cladding used on the structure. In colder regions or older homes, it is advisable to choose a high-perm house wrap, such as Tyvek, which has a perm rating of around 54. This rating indicates the material's ability to allow water vapor to escape, reducing the risk of condensation and moisture buildup within the wall cavity. Lower-perm house wraps, typically rated between 8 and 12, may not perform as well in these conditions and can lead to issues such as frost formation and damp sheathing.
In addition to perm ratings, it is important to consider the durability and breathability of the house wrap. A high-perm product not only facilitates moisture management but also contributes to long-term energy efficiency by maintaining dry and well-insulated walls. When making a selection, consult with manufacturers' guidelines and, if possible, use tools such as a system selector tool to ensure compatibility with the chosen cladding and climate conditions.
Preparing for Installation
Before unrolling the house wrap, it is essential to prepare the wall assembly to ensure a smooth and effective installation. One key step is priming or sealing the back of wood siding boards before they are installed. This helps prevent water from wicking into the wood and peeling the paint or finish. Although this step may seem minor, it plays a critical role in protecting the longevity of the siding and the overall aesthetic of the home.
Another important consideration is the coordination with subcontractors. If you are the general contractor, it is advisable to have an extra roll of house wrap on site for use by framers, electricians, and other subcontractors who may attach objects to the wall. This includes soffit stringers, trim boards, and electrical meters. Providing clear instructions for installing the house wrap in these areas helps prevent gaps and ensures a continuous barrier.
Installation Techniques and Best Practices
Cutting and Handling the House Wrap
A practical tip for handling house wrap is to cut full rolls into more manageable sizes, particularly on windy days. Using a circular saw to cut the roll as deeply as possible and then twisting the roll until the cut is complete can make the material easier to handle. While this process results in more tape being used for horizontal seams, the labor savings and reduced frustration during installation make it worthwhile.
For smaller sections and tight corners, a sharp utility knife is effective for cutting house wrap. However, care must be taken to avoid crumpling the roll during the final cut. A recommended technique is to start the cut in the middle of the roll, cut one half while leaving a 1-inch hinge, and then cut the other half. This method allows for a smoother edge and reduces the likelihood of wrinkles, which can trap water and lead to moisture issues.
Securing and Fastening the House Wrap
The use of cap nails or cap staples is now a standard requirement for house wrap installation. Unlike traditional staples, capped fasteners hold the house wrap to the wall up to 25 times better, ensuring that it remains in place even during strong winds. This is particularly important in high-wind zones where the risk of the material being blown loose is higher.
To install capped fasteners efficiently, a Stinger® Cap Staple Hammer is recommended. This tool functions similarly to a standard hammer-tacker and allows for quick and consistent fastening. While the initial setup may require a few practice shots to master, the speed and reliability of the tool make it a preferred option for most DIY house wrap projects.
Sealing Seams and Penetrations
Sealing seams is a critical step in ensuring the effectiveness of the house wrap. Each joint should be overlapped by at least 6 inches, with 8 inches being the recommended overlap in high-wind areas. This overlap mimics the way shingles are laid, directing water downward and away from the wall assembly. The use of 3-inch tape is recommended for sealing these seams, as it provides a wider bonding surface and ensures a more secure and weather-tight seal.
In addition to sealing vertical and horizontal seams, it is important to tape around every wall penetration. This includes pipes, vents, and other objects that pass through the wall. The process involves cutting the house wrap around the penetration, angling the cuts to allow for flexibility, and then applying tape to secure the material in place. Regular house wrap tape is typically sufficient for these applications, though it is essential to ensure that the tape extends at least 1 inch on each side of the penetration.
Handling Window and Door Openings
Window and door openings require special attention during house wrap installation. The traditional method of cutting out the opening and moving on may seem efficient, but it can lead to gaps and poor sealing. A more effective approach is to make a central vertical cut, followed by cuts at the top and bottom of the opening to create two flaps. These flaps should be wrapped inside the building, past the jack stud, before cutting off the excess. At the top, an angled cut should be made, and the flap can be temporarily held in place with tape. This method not only meets the requirements of most window manufacturers but also ensures that the inspector will be satisfied with the installation.
For existing windows and doors, it is necessary to apply butyl-style tape directly to the edge of the brick mold or window itself. This process can be time-consuming, especially when using super-sticky tape, but it is essential for creating a continuous and sealed barrier. A useful tip is to apply the tape in sections rather than peeling off the entire backing at once, which can help reduce the risk of the tape slipping or misaligning during installation.
Addressing Common Mistakes
One of the most common mistakes in house wrap installation is the presence of wrinkles. These not only look unprofessional but also create areas where water can be trapped, leading to moisture issues over time. To avoid this, it is recommended to start a new course by tacking a few capped fasteners in the center of the roll, then rolling out several feet and adjusting the sheet as needed before securing the rest. This method ensures a smooth and wrinkle-free installation.
Another mistake to avoid is cutting out window openings in the traditional manner. While this may be quicker, it often results in gaps that can allow water to enter the wall cavity. By following the recommended method of creating flaps and angling the cuts, the risk of water infiltration is significantly reduced, and the overall performance of the building envelope is improved.
Conclusion
Proper installation of house wrap is essential for achieving an energy-efficient and moisture-resistant building envelope. By selecting the right material, preparing the wall assembly, and following best practices for cutting, fastening, and sealing, homeowners and contractors can ensure that their homes are protected from the elements. Attention to detail, especially around window and door openings and wall penetrations, can make a significant difference in the long-term performance of the structure. With the right approach and tools, house wrap installation can be both efficient and effective, contributing to a durable and comfortable living environment.