Deck Waterproofing Systems & Coatings for Long-Term Protection

Where Waterproof Deck Systems Are Used

Waterproof deck systems are used anywhere an exterior walking surface must resist moisture while protecting the construction below. Common applications include:

• Apartment, condominium, and hotel balconies.
• Roof decks and decks located over occupied living space.
• Exterior corridors, breezeways, and pedestrian walkways.
• Stairs, landings, entryways, and plazas.
• Pool decks and walkways around spas.
• Parking structures and elevated concrete decks.
• Residential, multifamily, hospitality, office, and other commercial properties.
• New construction, renovation, and qualified deck-restoration projects.

The location alone does not determine the right system. Substrate type, structural condition, drainage, traffic, exposure, local code requirements, and the desired finish must also be considered.

Key Benefits of Waterproof Deck Systems

A complete deck waterproofing system can offer several advantages over relying on a standalone coating or surface finish:

• Long-term moisture protection: A coordinated assembly helps prevent water from reaching vulnerable seams, substrates, and spaces below.
• Durable walking surfaces: Reinforced layers and compatible topcoats help withstand pedestrian traffic, weather, and ultraviolet exposure.
• Substrate-specific performance: Systems are engineered for plywood, concrete, or underlayment applications rather than used as one-size-fits-all solutions.
• Seamless coverage: Monolithic and reinforced assemblies reduce weak points across the finished deck surface.
• Design flexibility: Color, texture, decorative, skid-resistant, and solar-reflective options are available for selected systems.
• Restoration potential: Certain systems may be suitable for rehabilitating existing deck surfaces after professional inspection and preparation.
• Code and project support: Selected Westcoat systems have published evaluations, fire ratings, and specification resources to support project planning.
• Coordinated maintenance: Routine inspection, cleaning, and scheduled recoating can help preserve appearance and waterproofing performance.

How to Choose the Right Waterproof Deck System

Choosing the right waterproof deck system depends on:

• Whether the substrate is plywood, reinforced plywood, or concrete.
• Whether the deck is new construction or an existing surface being restored.
• Whether the waterproof layer will be the finished walking surface or an underlayment beneath tile, stone, or concrete.
• The expected level of pedestrian or vehicular traffic.
• Exposure to sun, rain, temperature changes, pool water, and other site conditions.
• The deck’s slope, drainage layout, flashing, railings, penetrations, and transitions.
• Required fire ratings, evaluation reports, building codes, and project specifications.
• Desired color, texture, slip resistance, decorative appearance, or solar reflectivity.
• Warranty requirements and the qualifications required of the installer.
• The inspection and maintenance plan for the completed deck.

A qualified professional should inspect the substrate and project details before a system is specified. Westcoat waterproof deck systems are for professional use and should be installed according to the current system specification by a properly trained, equipped, and licensed applicator.

Waterproof Decking Systems for Plywood

Plywood deck waterproofing systems are designed for balconies, roof decks, walkways, and other elevated walking surfaces framed with exterior-grade plywood. Reinforcement helps bridge plywood seams and creates a unified surface, while the membrane, cementitious layers, and topcoat work together to resist water intrusion and wear.

• ALX™: One-hour fire-rated and wildland-urban interface compliant, recommended for balcony and roofway decks and on walkways.
• ALX Solar Reflective Finish: Beautiful, with a reflective finish that lowers temperatures, excellent for balcony decks, roof decks, and walkways.
• ALX Pro: With a reinforced membrane and an optional 20-year warranty, best on balcony decks, roof decks, and walkways.
• ALX Pro Solar Reflective Finish: With a reflective finish that lowers temperatures and an additional reinforced membrane layer, best for balcony decks, roof decks, and walkways.
• Shur Deck™ and Shur Deck Pro: seamless, monolithic membrane that protects from water intrusion and long-term wear, recommended for balcony decks, walkways, and other elevated surfaces.
• Mer-ko: A floating, slip-sheet waterproofing solution designed for exterior decks, balconies, and walking surfaces.

Waterproof Deck Coating Systems for Concrete

Concrete deck waterproofing systems are designed for elevated concrete surfaces where moisture, weather, and regular foot traffic can lead to cracking, wear, or water intrusion. Depending on the application, a reinforced system can be installed on a new deck or used to rehabilitate an existing surface after proper evaluation and preparation.

• MACoat™: Flexible, with color and skid-resistant texture options, recommended for balcony decks, as well as garages and walkways.
• MACoat Solar Reflective Finish: Lowers surface temperature and resists the urban heat island effect, best for balcony and roof decks, garages, and walkways.
• Shur Deck Over Concrete: Designed to protect and enhance exterior concrete surfaces, excellent for balconies, rooftop decks, and walkways.
• Mer-ko: A floating, slip-sheet waterproofing solution designed for exterior decks, balconies, and walking surfaces.

Under Deck Waterproofing Systems

The phrase “under deck waterproofing system” can describe two different solutions. Some products are drainage panels installed beneath an open deck. Westcoat systems instead waterproof the walking surface above or serve as an underlayment beneath tile, stone, or concrete. By stopping water at the deck surface, these assemblies help protect the substrate, supporting structure, and occupied area below.

• ALX™ Waterproofing Underlayment: Designed for plywood decks that will receive tile, stone, or concrete, including exterior balconies and decks over living space.

• MACoat™ Waterproofing Underlayment: Designed for under-tile and between-slab applications on suitable concrete surfaces, including balconies, entryways, walkways, and parking structures.

For waterproof under deck systems to perform as intended, the entire assembly must account for the substrate, slope, drains, flashing, penetrations, transitions, and final finish. A Westcoat representative or qualified applicator can help identify the appropriate system and details for the project.