A characteristic of mechanically attached roof membranes is they are subject to:

A characteristic of mechanically attached roof membranes is they are subject to:

• A. Thermal expansion
• B. Vertical displacement
• C. Moisture migration
• D. Wind uplift

Answer: (B)

Mechanically attached roof membranes are secured to the deck at discrete points with fasteners or clips, not bonded over the entire area. Because of this, the membrane can move vertically relative to the deck between those attachment points when subject to loads. Wind forces and temperature changes can cause the sheet to lift and settle between fasteners, so vertical movement is a defining behavior of this type of system. This vertical displacement is the practical outcome designers must account for with proper fastener spacing, edge detailing, and layout to maintain performance.

Mechanically attached roof membranes are secured to the deck at discrete points with fasteners or clips, not bonded over the entire area. Because of this, the membrane can move vertically relative to the deck between those attachment points when subject to loads. Wind forces and temperature changes can cause the sheet to lift and settle between fasteners, so vertical movement is a defining behavior of this type of system. This vertical displacement is the practical outcome designers must account for with proper fastener spacing, edge detailing, and layout to maintain performance.