Deck Coating Formulations: Acrylics, Cementitious coatings, Epoxy, Asphalt overlay, Latex, Neoprene, Hypalon, Urethane
Acrylics are not waterproof coatings, but act as water-repellent sealers. Their use is primarily aesthetic, to cover surface defects and cracking in decks. These coatings have low elastomeric capabilities; silica aggregate is premixed directly into their formulations, which further lowers their elastic properties. These two characteristics prevent acrylics from being true waterproof coatings.
The inherent properties of acrylics protect areas such as walkways or balconies with no occupied areas beneath from water and chloride penetration. In addition to concrete sub- strates, acrylics are used over wood or metal substrates, provided that recommended primers are installed. Acrylics are also used at slab-on-grade areas where urethane coatings are not recommended.
Sand added in acrylic deck coatings provides excellent antislip finishes. As such, they are used around pools or areas subject to wet conditions that require protection against slips and falls. Acrylics are not recommended for areas subject to vehicular traffic. Some manufacturers allow their use over asphaltic pavement subject only to foot traffic, for aesthetics and a skid-resistant finish. (See Table 3.14.)
Cementitious deck coatings are used for applications over concrete substrates and include an abrasive aggregate for exposure to traffic. These materials are supplied in prepacked and premixed formulations requiring only water for mixing. Cementitious coatings are applied by trowel, spray, or squeegee, the latter being a self-leveling method.
Cementitious systems contain proprietary chemicals to provide necessary bonding and waterproofing characteristics. These are applied to a thickness of approximately 1 8 in and will fill minor voids in a substrate. A disadvantage of cementitious coatings, like below- grade cementitious systems, is their inability to withstand substrate movement or cracking.
They are one-step applications, with integral wearing surfaces, which require no primers and are applicable over damp concrete surfaces.
Modified acrylic cementitious coatings are also available. Such systems typically include a reinforcing mesh embedded into the first coat to improve crack-bridging capabilities. Acrylics are added to the basic cement and sand mixture to improve bonding and performance characteristics.
Cementitious membrane applications include the dry-shake and power-trowel methods previously discussed in Chap. 2. Successful applications depend on properly designed, detailed, and installed allowances for movement, both thermal and differential. For cementitious membranes to be integrated into a building envelope, installations should include manufacturer-supplied products for cants, patching, penetrations, and terminations. (See Table 3.15.)
As with acrylics, epoxy coatings are generally not considered true waterproof coatings.
They are not recommended for exterior installations due to their poor resistance to ultraviolet weathering. Epoxy floor coatings have very high tensile strengths, resulting in low elastomeric capabilities. These coatings are very brittle and will crack under any movement, including thermal and structural.
Epoxy coatings are used primarily for interior applications subject to chemicals or harsh conditions such as waste and water treatment plants, hospitals, and manufacturing facilities. For interior applications not subject to movement, epoxy floor coatings provide effective waterproofing at mechanical room floor, shower, and locker room applications.
Epoxy coatings are available in a variety of finishes, colors, and textures, and may be roller- or trowel-applied.
Epoxy deck coatings are also used as top coats over a base-coat waterproof membrane of urethane or latex. However, low-movement capabilities and brittleness of epoxy coatings limit elastomeric qualities of waterproof top coats. (See Table 3.16.)
Asphalt overlay systems provide an asphalt wearing surface over a liquid-applied membrane. The waterproofing base coat is a rubberized asphalt or latex membrane that can withstand the heat created during installation of the asphalt protective course. Both the waterproof membrane and the asphalt layers are hot-applied systems.
Asphalt layers are approximately 2 in thick. These systems have better wearing capabilities due to the asphaltic overlay protecting the waterproof base coating.
The additional weight added to a structure by these systems must be calculated to ensure that an existing parking garage can withstand the additional dead loads that are created.
Asphalt severely restricts the capability of the waterproof membrane coating to bridge cracks or to adjust to thermal movement. Additionally, it is difficult to repair the waterproofing membrane layers once the asphalt is installed. There is no way to remove overlays without destroying the base coat membrane. Asphaltic systems are not recoatable. For maintenance, they must be completely removed and reinstalled. (See Table 3.17.)
Latex, neoprene, hypalon
Deck coatings are available in synthetic rubber formulations, including latex, neoprene, neoprene cement, and hypalon. These formulations include proprietary extenders, pigments, and stabilizers. Neoprene derivatives are soft, low-tensile materials and require the addition of a fabric or fiberglass reinforcing mesh. For traffic-wear resistance, this reinforcing mesh enhances in-place performance properties such as elongation and crack-bridging capabilities.
Reinforcing requires that the products be trowel applied rather than roller or squeegee applied.
Trowel application and a finish product thickness of approximately 1 4 in increase the in-place costs of these membranes. They also require experienced mechanics to install the rubber derivative systems. Trowel applications, various derivatives, and proprietary formulations provide designers with a wide range of textures, finishes, and colors.
Rubber compound coatings have better chemical resistance than most other deck-coating systems. They are manufactured for installation in harsh environmental conditions such as manufacturing plants, hospitals, and mechanical rooms. They are appropriate in both exterior and interior applications.
Design allowances must be provided for finished application thickness. Deck protrusions, joints, wall-to-floor details, and equipment supports must be flashed and reinforced for membrane continuity and watertightness. Certain derivatives of synthetic rubbers become brittle under aging and ultraviolet weathering, which hinders waterproofing capabilities after installation. Manufacturer’s literature and applicable test results should be reviewed for appropriate coating selection. (See Table 3.18.)
Urethane deck coatings are frequently used for exterior deck waterproofing. These are available for both pedestrian and vehicular areas in a variety of colors and finishes. Urethane systems include aromatic, aliphatic, and epoxy-modified derivatives and formulations.
Aliphatic materials have up to three times the tensile strength of aromatics but only 50 percent of aromatic elongation capability. Many manufacturers use combinations of these two materials for their deck-coating systems. Aromatic materials are installed as base coats for better movement and recovery capabilities; aliphatic urethane top coats make for better weathering, impact resistance, and ultraviolet resistance.
Epoxy urethane systems are also used as top coat materials. These modified urethane systems provide additional weathering and wear, while still maintaining necessary waterproofing capabilities.
Urethane coatings are applied in two or more coats, depending upon the expected traffic wear. Aggregate is added in the final coating for a nonslip wearing surface. An installation advantage with urethane systems is their self-flashing capability. Liquid-applied coatings by brush application are turned up adjoining areas at wall-to-floor junctions, piping penetrations, and equipment supports and into drains.
Urethane coatings are manufactured in self-leveling formulations for applications control of millage on horizontal surfaces. Nonflow or detailing grades are available for vertical or sloped areas. The uncured self-leveling coating is applied by notched squeegees to control thickness on horizontal areas. At sloped areas, such as the up and down ramps of parking garages or vertical risers of stairways, nonflow material application ensures proper millage. If self-leveling grade is used in these situations, material will flow downward and insufficient millage at upper areas of the vertical or sloped portions will occur.
Nonflow liquid material is used to detail cracks in concrete decks before deck-coating application. Cracks wider than 1 /16 in, which is the maximum width that urethane materials bridge without failure, are sawn out and sealed with a urethane sealant. This area is then detailed 4 in wide with nonflow coating.
In addition, urethane coatings are compatible with urethane sealants used for cants between vertical and horizontal junctions, providing a smooth transition in these and other changes of plane. This is similar to using wood cants for roof perimeter details (see Table 3.19).