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 elastomeric 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.