What is required over a solid deck for structural metal roofing installation?

Underlayment is required over a solid deck for structural metal roofing installation because it serves several essential functions that enhance the performance and longevity of the roofing system.

First, underlayment acts as a secondary line of defense against water infiltration. It provides a waterproof barrier beneath the metal roof, protecting the underlying structure, insulation, and living spaces from potential leaks or moisture. This is particularly important in areas prone to rain or snow, where water penetration can cause significant damage over time.

Second, the underlayment helps to control temperature fluctuations and condensation. In metal roofing, which can heat up quickly when exposed to sunlight, there is a risk of condensation forming on the underside of the roof. Underlayment can help manage this condensation, preventing it from dripping onto the decking or into the building.

Finally, underlayment provides a smoother surface for the metal panels to be installed over, reducing potential issues that could arise from irregularities in the solid deck. This assists in ensuring a proper seal and alignment during the installation process.

Overall, underlayment is a critical component in optimizing the durability and performance of metal roofing systems when installed over solid decks.