House wrap is a protective material used on the exterior walls of a building to prevent air and moisture infiltration into the structure. It acts as a secondary defense against the elements and helps improve the energy efficiency of a home. While house wrap is commonly installed on walls, there may be instances when you wonder if it is possible to install it under a roof. In this article, we will explore whether installing house wrap under a roof is a viable option.
Understanding House Wrap:
Before discussing whether house wrap can be installed under a roof, let’s take a closer look at what house wrap is and its purpose. House wrap is typically made of a polyethylene or polypropylene material that is permeable to allow air and water vapor to escape while keeping water out. It is designed to prevent moisture accumulation within the wall cavity, which can lead to mold growth and damage to the structure.
The Role of House Wrap:
House wrap is an essential component in home construction as it helps to create a weather-resistant barrier. It is typically installed directly over the sheathing and under the exterior cladding, such as siding or brick. Its primary function is to protect the building envelope from moisture, wind, and drafts, while remaining breathable to allow any trapped moisture to escape.
The Purpose of Roofing Underlayment:
To understand whether house wrap can be installed under a roof, we need to consider the purposes of the roofing underlayment. Roofing underlayment is a material installed directly onto the roof deck before the final roofing material is applied. It serves as an extra layer of protection against water infiltration and ice dams. Additionally, it can also provide temporary weather protection during the construction process.
Different Types of Roofing Underlayment:
There are various types of roofing underlayment available, including asphalt-saturated felt, synthetic underlayment, and rubberized asphalt underlayment. Each type serves the same primary purpose, which is to prevent water intrusion. The choice of underlayment depends on factors such as climate, cost, and local building codes.
Potential Issues with Installing House Wrap Under a Roof:
While house wrap has proven effective as an exterior wall covering, there are several reasons why it is not typically used as an underlayment for roofs.
- Water Resistance: Unlike roofing underlayment, house wrap is not specifically designed to resist prolonged exposure to water. Roofing underlayment, especially those made of rubberized asphalt, are more capable of withstanding extreme weather conditions and ensuring that water does not penetrate the roof deck.
- Wind Uplift: Roofing underlayment is engineered to resist wind uplift. It is installed in a manner that integrates with the rest of the roof system, providing increased structural stability during high winds. House wrap, on the other hand, is not designed or tested for this specific purpose, and its performance may be compromised if used under a roof.
- Breathability: While house wrap allows moisture inside a wall to escape, it is not designed to allow trapped moisture in the attic or roof space to ventilate properly. Roofing underlayment, such as synthetic materials, are specifically engineered to allow vapor transmission while still providing a barrier against liquid water intrusion.While house wrap is an essential barrier against moisture and air infiltration in wall construction, it is not typically recommended or designed to be used as an underlayment for roofs. Roofing underlayment is specifically engineered to withstand the unique challenges of roofing applications, including water resistance, wind uplift, and proper ventilation. Therefore, it is best to utilize appropriate roofing underlayment materials that are designed and tested for optimal performance under various weather conditions.