In a mechanically attached roofing system, how is the roof load primarily carried?

• A. By adhesive bonds between membrane and deck
• B. By the membrane's own weight only
• C. Through fasteners anchoring the membrane to the deck
• D. By drainage and water weight

Answer: (C)

In a mechanically attached roof, the main way the roof loads are carried is through the fasteners that anchor the membrane to the deck. When wind uplift tries to lift the roof, those fasteners pull the membrane down into the deck, transferring the forces into the structural substrate. The membrane’s own weight is a small constant dead load and doesn’t provide the primary uplift resistance, and adhesive bonds aren’t the primary load path in this system (they’re more central in fully adhered systems). Water weight and drainage contribute to overall roof load, but they don’t serve as the primary mechanism for resisting uplift.