1-Hour vs 2-Hour Fire Rated Drywall Assemblies: What Specifiers Need to Know A fire rated drywall wall is only as good as the assembly it forms. The same board can deliver a one-hour or a two-hour rating depending on layers, thickness, framing, insulation and fastening. The rating is a property of the system — never of the panel alone. How Each Rating Is Achieved Assembly Typical Build-Up Approx. Rating Single layer, one face 15.9 mm Type X 30–60 min Single layer, both faces