While metal roofing is generally known for its durability and secure fastening to the roof deck, it may not be suitable for low slope roofs due to certain factors that can affect its performance and longevity. Here are some reasons why some metal roofs are not rated for low slope roofs:
Water Accumulation: On low slope roofs, water has a tendency to accumulate and stand for longer periods, especially during heavy rain or snow. If water pools on the metal roof for an extended time, it can lead to corrosion and the breakdown of protective coatings, potentially causing leaks and premature deterioration.
Increased Stress on Fasteners: Low slope roofs experience higher wind uplift forces and may be subject to greater thermal movement compared to steeper roofs. The increased stress on the fasteners holding the metal panels in place can lead to loosening over time, potentially causing leaks and reducing the roof's overall integrity.
Improper Water Drainage: Metal roofs are designed to shed water efficiently. On steep-slope roofs, gravity helps water flow downward and away from the roof. However, on low slope roofs, water drainage may be less effective, leading to water infiltration and potential water-related issues.
Manufacturer Specifications: Some metal roofing manufacturers provide specific guidelines for the minimum slope at which their roofing products should be installed. Deviating from these recommendations can void warranties and compromise the roof's performance.
Roofing Material and Design: Not all metal roofing materials are suitable for low slope roofs. Some metal roofing profiles and materials may not have the necessary design features or seam systems to effectively shed water on low slope installations.
Code and Safety Compliance: Building codes and safety standards may have specific requirements for roofing materials based on the roof's slope. Installing a metal roof on a low slope may not meet these requirements and could lead to potential legal and insurance issues.
Ice and Snow Buildup: On low slope roofs, ice and snow can accumulate, causing ice dams and snow drifts. These conditions can lead to additional stress on the metal roof and its fasteners, potentially causing damage.
It's important to consult with a professional roofing contractor who can assess your specific roof design and local weather conditions. They can recommend the most suitable roofing material and slope for your home to ensure long-term performance and protection. In some cases, there are metal roofing products specifically designed for low slope applications, so it's essential to choose the appropriate material that matches your roof's characteristics.