Protected Membrane Roofs and Plaza Decks

A special type of low-slope roof system is the protected membrane roof (PMR). In this system, extruded polystyrene insulation boards are placed above the membrane.
The insulating boards are then covered with aggregate or concrete paver ballast. (If aggregate is used, a fabric mat is first placed over the insulation.) This construction protects the membrane from mechanical damage (dropped tools, wind-blown debris) and from direct exposure to the weather (UV, high and low temperatures). Figure 12.2 illustrates a PMR that incorporates a built-up membrane.
Plaza decks are similar to protected membrane roofs, except that they are designed for heavy traffic loads. Because of the difficulty in repairing these types of roof systems, they should be designed and constructed with care. If this is done, they can provide a long and successful service life.
Application of Roofing. If a roof has been adequately designed and quality materials have been specified and provided, the next step toward achieving a successful roof is to have it installed by a reputable roofing contractor. After a contractor has been retained to perform the work, the following items are of importance.