Roof Sheathing and Moisture Management Considerations for Slope

While many homeowners focus on the roof as an extension of the home’s design and curb appeal, builders know a roofing system is the first line of defense against all the elements Mother Nature throws our way. As you work with your homebuyers, let’s explore the primary factors you need to consider for roof sheathing and moisture management based on roofing type and slope.  

Challenges in Roof Slope Water Drainage

“Roofs have become complicated,” says Neil Freidberg, Building Science Manager at LP Building Solutions. “The standard gable roof that sheds in two directions no longer exists in most new home builds.” This is one of the reasons why roofing systems require careful thought in regard to moisture management for longer-lasting protection. 

One of the biggest challenges of modern roof designs is that one area will be exposed to the sun and another will not. 

While multiple edges and slopes create visual interest, it also produces an opportunity for moisture to collect on the surface. With these architectural and design styles the western and southern slopes often dry out quickly while other roof areas may see prolonged exposure to any accumulated moisture. 

“If a roof structure is incorrectly designed or chopped up some areas might never see sun or experience air movement, which causes condensation on the surface,” says Freidberg. “Depending on the climate, sun exposure dries moisture from underneath. But moisture can remain on the north side of the attic.” 

Since maintaining proper airflow is one of the best ways to combat moisture collection, Freidberg recommends attic ventilation: “You can do that mechanically with an attic fan or passively with soffit.” LP® SmartSide® Soffit resists fungal decay and is an excellent choice for areas where high humidity, sun, snow or termites can take a toll on a home.

“Without protection or a means to remove bulk condensation, sooner or later it could make its way into the OSB and cause failure,” cautions Freidberg. “This is why we want a properly designed building.”

Water-Resistant Roof Sheathing for Sloped Roof

Builders may want to consider upgrading to a product, like LP WeatherLogic® Air & Water Barrier, that simplifies the process of installing a water-resistive roof underlayment by combining roof sheathing and underlayment. 

“Another one of the great benefits of LP WeatherLogic sheathing is that it can be installed under composite shingles, tiles, standing seam metal roofs––almost anything permitted in the code,” says Freidberg. Keep in mind that LP WeatherLogic panels cannot be used as the roof underlayment on low-slope roofs (< 2:12 roof pitch). 

For builders in climate zones 1-4, builders can use LP® TechShield® Radiant Barrier with an underlayment on top. LP TechShield sheathing has no limitations on roof type either––it can be installed under a variety of roofing materials and degrees of slope. 

For optimum water drainage, be sure to review the installation guidelines for roof transitions and eaves when installing LP Structural Solutions products.  

Review more ways roofing materials can deliver strength and keep moisture out.