With certain designs, horizontal above-grade decks require the same waterproofing protection as below-grade areas subjected to water table conditions. At these areas, membranes are chosen in much the same way as below-grade applications. These installations require a protection layer, since these materials cannot be subjected to traffic wear or direct expo- sure to the elements. As such, a concrete topping slab is installed over the membrane, sandwiching the membrane between two layers of concrete; hence the name sandwich-slab membrane. Figure 3.51 details a typical sandwich-slab membrane.

FIGURE 3.51 Typical sandwich-slab membrane detailing. (Courtesy of TC MiraDRI)

In addition to concrete layers, other forms of protection are used, including wood decking, concrete pavers (Fig. 3.52), natural stone pavers (Fig. 3.53), and brick pavers (3.54). Protected membranes are chosen for areas subjected to wear that deck coatings are not able to withstand, for areas of excessive movement, and to prevent the need for excess maintenance. Although they cost more initially due to the protection layer and other detailing required, sandwich membranes do not require the in-place maintenance of deck coatings or sealers.

FIGURE 3.52 Protected membrane application using concrete pavers. (Courtesy of American Hydrotech)
FIGURE 3.53 Protected membrane application using stone pavers. (Courtesy of TC MiraDRI)
FIGURE 3.55 Insulation layer in protected membrane application. (Courtesy of American Hydrotech)
Protected membranes allow for installation of insulation over waterproof membranes and beneath the topping layer (Fig. 3.55). This allows occupied areas beneath a deck to be insulated for environmental control. All below-grade waterproofing systems, with the exception of hydros clay and vapor barriers, are used for protected membranes above grade. These include cementitious, fluid-applied, and sheet-good systems, both adhering and loose-laid. Additionally, hydros clay systems have been manufactured attached tosheet-good membranes, applicable for use as protected membrane installations.

FIGURE 3.55 Insulation layer in protected membrane application. (Courtesy of American Hydrotech)

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