When new roof coverings are applied and a combustive concealed space is created, which material must cover the existing surface?

When new roof coverings are applied over an existing surface that creates a combustive concealed space, it is essential to cover that existing surface with a non-combustible material to mitigate fire risks. Gypsum board is particularly suitable for this purpose due to its inherent properties.

Gypsum board is made from non-combustible materials and has a high fire-resistance rating, which helps to inhibit the spread of flames and protects the underlying structure from heat. This characteristic is critically important in concealed spaces, as these areas can be difficult to access and are susceptible to fires if not properly protected.

While other materials like plywood, fiberboard, and OSB board may have their own applications in roofing, they do not provide the same level of fire resistance as gypsum board. Therefore, using gypsum board ensures compliance with safety regulations and enhances the fire safety of the roofing system.