Which of the following conditions can lead to slippage of a built-up roof membrane?

The correct answer revolves around the impact of using the wrong type of asphalt, as it directly influences the adhesion and stability of the built-up roof membrane. Built-up roofs rely on asphalt as a bonding agent that holds the various layers of the membrane together. If a type of asphalt that does not match the specifications for the membrane is used, it can lead to insufficient adhesion between layers. This compromised bond can cause slippage, where the roofing layers shift out of position due to inadequate grip, especially under dynamic conditions such as temperature changes or physical stress.

Understanding why other conditions do not lead to slippage is also essential. High temperatures and humidity can affect the roofing materials, potentially softening them, but they do not inherently cause slippage if the materials are specified and applied correctly. Exposure to sunlight can lead to degradation over time, but it does not immediately lead to slippage; rather, it could potentially weaken the materials in the long term. Insufficient overlapping of membranes can lead to water ingress and may compromise the roof’s integrity, but it is the type of asphalt that fundamentally affects the bonding strength of the layers, making the wrong type the key factor in slippage.