In roofing assemblies for low-slope concrete roof decks, Protected Membrane Roofs set the bar for cost savings, labor efficiency, and roof life span among other advantages. These, advantages may appear counterintuitive: common sense suggests the roof's waterproofing covering needs to be on top, protecting all the other components of the assembly from the elements of nature, including the insulation. Nonetheless, the primary moisture barrier (or waterproof roof covering) itself tends to be the weak link when exposed to environmental stress. 

When the waterproof membrane is on top of insulation, the relative expansion and contraction of the roofing assembly due to thermal cycling can be detrimental to roof longevity. Conversely, on a 'typical' roof, hailstorms and maintenance foot traffic both bear potential of mechanically damaging an exposed roof membrane. Additionally, the waterproofing membrane on top of the insulation can act as a vapor barrier, allowing moisture to accumulate in and around the insulation beneath the membrane, causing a whole different set of problems. For these and many other reasons, Protected Membrane Roofing Assemblies are beneficial and desirable in modern building and construction.