Section 14: PLAZA WATERPROOFING
System Description. Since it is impossible to keep all
the water out all the time, the basic plaza waterproofing system
must be designed to excrete water that does get in, without
damage to the interior spaces below.
Options. Plaza waterproofing basic membrane options
include hot-applied built-up roof membrane, elastomeric sheet,
and liquid-applied waterproofing.
Materials. Of the three basic membrane types, the hot
applied built-up bituminous offers the most advantages:
Multiple lines of waterproofing defense (via
alternating layers of felt and bitumen);
Adaptability to hot-applied protection boards;
Excellent adhesion to concrete substrates;
Familiarity to waterproofing mechanics;
Known performance criteria.
Planters. Planters are notorious for leakage. Whether
precast or poured-in-place, they should not interrupt the main
deck waterproofing. If poured-in-place planters are selected,
they must be handled as a perimeter flashing. Precast planters
are recommended. Never locate a planter across an expansion
Minimum Slope. Provide minimum 1/4 inch
per foot (2
percent) slope, built into base slab (1/2 inch per
percent) is preferred). Do not rely on additional
provide slope. Provide crickets between drains at
Joint Construction. Specify all joint construction
with "watershed" concept in base slab (refer to ASTM C 981).
These raised sections keep water freely drained from these very
critical areas. All perimeter construction and expansion joints
should be provided with appropriately shaped preformed joint
formers flashed into adjoining membrane.