Page 116 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.5
small cracks, to high-strength, quick-set cementitious patching compounds for repairing
spalled substrate areas.

HORIZONTAL APPLICATIONS

Several types of systems and products are available for horizontal above-grade applica-
tions, such as parking garages and plaza decks. Surface coatings, which apply directly to
exposed surfaces of horizontal substrates, are available in clear siloxane types or solid
coatings of urethane or epoxy. Clear horizontal sealers, as with vertical applications, do not
change existing substrate aesthetics to which they are applied. They are, however, not in
themselves completely waterproof but only water-resistant.
Clear coatings are often specified for applications, to prevent chloride ion penetration
into concrete substrates from such materials as road salts. These pollutants attack rein-
forcing steel in concrete substrates and cause spalling and structural deterioration.
Urethane, epoxy, or acrylic coatings change the aesthetics of a substrate but have elas-
tomeric properties that allow bridging of minor cracking or substrate movement. Typically,
these coatings have a “wearing coat” that contains silicon sand or carbide, which allows
vehicle or foot traffic while protecting the waterproof base coat.
Subjecting coatings to foot or vehicular wear requires maintenance at regular frequency
and completion of necessary repairs. The frequency and repairs are dependent on the
type and quantity of traffic occurring over the envelope coating.
As with vertical materials, attention to detailing is necessary to ensure watertightness.
Expansion or control joints must be properly sealed, cracks or spalls in the concrete must
be repaired before application, and allowances for drainage must be created.
Several types of waterproof membranes are available for covered decks such as sand-
wich slab construction or tile-topped decks. These membranes are similar to those used in
below-grade applications, including liquid-applied and sheet-good membranes. Such
applications are also used as modified roofing systems.

ABOVE-GRADE EXPOSURE PROBLEMS

All above-grade waterproof systems are vulnerable to a host of detrimental conditions due
to their exposure to weathering elements and substrate performance under these condi-
tions. Exposure of the entire above-grade building envelope requires resistance from many
severe effects, including the following:
● Ultraviolet weathering
● Wind loading
● Structural loading due to snow or water
● Freeze–thaw cycles
● Thermal movement