Page 176 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.65

FIGURE 3.56 Prefabricated drainage layer in sandwich application. Note the insulation is spaced to
permit drainage also. (Courtesy of TC MiraDRI)
It is imperative that termination detailing be adequately included to permit the drainage or
weeping of water at the edges or perimeter of the sandwich slab installation. This is usually
provided by installing an edge-weep system and counter-flashing, as shown in Fig. 3.60. Or
if the structural slab is sloped to drain towards the edges of the slab, a drain and gutter system
should be provided as shown in Fig. 3.61.
Note that in each of these details the drainage is designed to sweep water directly at the pre-
fabricated drainage board level. The drainage board should be installed so that the channels cre-
ated are all aligned and run towards the intended drainage. The entire purpose of the various
drainage systems in a sandwich-slab application (drainage mat, deck drains, and edge drainage
systems) can be entirely defeated if the pre-fabricated drainage board is not installed correctly.

DETAILING SANDWICH MEMBRANES

Expansion or control joints should be installed in both the structural slab portion and the pro-
tection layer. Providing for expansion only at the structural portion does not allow for thermal