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  • Writer's pictureJim Metzger

The Best Waterproofing Systems for Balconies, Decks and Walkways

Property owners and managers have plenty of options to choose from when it comes to waterproofing a deck or balcony. So how do you choose the best waterproofing product?


If you want to maximize the service life of your balcony or deck annual maintenance and a complete resurfacing every 5 years. Luckily several companies manufacture coatings and building materials that are used when waterproofing decks and balconies. Manufacturers have created code-compliant waterproofing systems for plywood subfloors and concrete deck surfaces. Each system offers impressive waterproofing performance when they are installed correctly. So how do homeowners and property managers know what system to choose? There are plenty of options to choose from so I’ve written this article to help you make a decision. In this article I will review products from Advance Flooring Products (AFP) of Benicia, CA, and why you should consider their products for your decking project.

The Best Waterproofing Systems

Flex-Dek

AFP’s Flex-Dek is a metal lath-reinforced deck system installed with a series of three separate applications. Flex-Dek combines a flexible, waterproofing, resin-bonding fiberglass between two cementitious applications. Flex-Dek is recommended where flexibility is essential during new construction settling, or where soft soil exists, to resist cracking. It is bonded together with specially formulated acrylic emulsion and sealed with Advance-Crete100% acrylic top coat.


Flex-Dek works only on plywood walking decks. It is recommended for the discriminating contractor or building owner who demands the finest in design, strength, and durability.

Flex-Dek is ideal for areas with heavy traffic or in cases where the elimination of plywood seams is essential. AFP’s Flex-Dek has been designed for balconies, corridors, stairs, and landings. It is regularly specified for hotels, condominiums, apartments, and office buildings. It can be stapled through most old deck systems to provide an excellent method for the rehabilitation of problem surfaces. Flex-Dek is low maintenance, economical, durable yet flexible, fast drying, and waterproof.


(Notice the 5-layers on this Flex-Dek PRO mock up)


The image above is a mock-up of the Flex-Dek system. Notice that new flashing has been installed along the wall and the perimeter of the deck. This means that the stucco on the wall will need to be repaired. All waterproofing replacement will cause the wall flashing to be replaced. Doors will have to be replaced and a new waterproof sheet metal pan installed under the new thresholds. This is the only way we can truly guarantee a fully sealed waterproofed layer.


Flex-Dek PRO

Like Flex-Dek, Flex-Dek PRO by AFP combines an acrylic fiber lath, with their superior resin base and concrete modifier. The difference between the two systems is that Flex-Dek PRO has two flexible slurry coats in the application process compared to one texture coat that Flex-Dek employs.


This system is one of the best products on the market because the layers offer redundancies in waterproofing. The metal lath also provides rigidity to the subfloor which helps prevent cracks over time. In the picture below you can see all the layers of the Flex-Deck PRO waterproof system including the lath, base coat, fiberglass mesh, first slurry coat, second slurry coat, and decorative finish. The base coat in Step 2 is a waterproof grout applied to the metal lath that bonds and seals the plywood. In Step 3, a fiber membrane is installed with a secondary waterproof resin to the base coat. Coats 5 and 6 are also waterproof coatings. The manufacturer warranty is a Joint Workmanship Warranty with applicators for up to 15 years.


The Flex-Dek PRO Waterproofing System is a premium product best suited for owners that want a product with best-in-class strength and durability. When installing from new, the Flex-Dek PRO system creates a strong system that is full of redundancies and decreases the likelihood of a leak. The fiberglass mesh gives the system unparalleled rigidity, a perfect solution for new decks and resurfacing preparations. The Waterproof mortar bed seeps into the metal lath and creates a waterproof barrier. For a second layer of protection, a fiber membrane is applied over the mortar bed with a special polymer that creates a secondary layer of waterproofing. The top layer is covered with lightweight mortar and deck paint is then tinted to the client’s color preference. The finish texture could be a broom finish which is easy to keep clean or a knockdown texture can be created for a decorative finish. This system comes with a Joint Workmanship Warranty with applicators for up to 15 years.


(Notice the 6-layers on this Flex-Dek PRO mock up)

The image above is a mock-up of the Flex-Dek PRO system. Notice that new flashing has been installed along the wall and the perimeter of the deck. This means that the stucco on the wall The image above is a mock-up of the Flex-Dek PRO system. Notice that new flashing has been installed along the wall and the perimeter of the deck. This means that the stucco on the wall will need to be repaired. All waterproofing replacement will cause the wall flashing to be replaced. Doors will have to be replaced and a new waterproof sheet metal pan installed under the new thresholds. This is the only way we can truly guarantee a fully sealed waterproofed layer.


What Causes Wood-Frame Damage on Balconies or Decks?


First let's discuss what causes leaks to manifest in the first place, more often than not flexion (or bending) is to blame. Flexion on the subfloor allows cracks to develop, and over time those cracks get large enough to allow water to penetrate down to the wood. So why does the subfloor flex? The subfloor flexes when people walk on it because the plywood is too thin. Plywood was relatively new in the 1960s and when those decks and walkways were built they used a 5/8 in. thick plywood for the subfloor. Now it is best practice to use a minimum of 3/4 in. CDX plywood, but we always recommend using a 1 1/8 in. tongue & groove CDX plywood if the budget allows. A rigid plywood will not allow the surface to flex, thus helping prevent cracks from developing.


(These two balconies have suffered years of neglect)

The other cause is the fact that the wear layer of the waterproofing system has been neglected and simply worn out. Evidence of this, is blistering surface, chipping of the mortar, and in some cases a hole. See the picture below captures the wear layer blistering and surface cracks forming where the deck surface meets the stair riser. The perimeter flashing shows rust. This type of rusting indicated that the flashing has corroded and is no longer waterproof. The dark staining on the wear layer shows where water pools and surface mold along with debris have darkened the wear layer.


Types of Decks that Require Waterproofing


The following decks are built out of wood frame construction. If the wood frame members are exposed to moisture, they will begin to rot. Structural engineers have designed 3 main types of decks detailed below. They all require a waterproof surface for protection from the elements.


Cantilever Walkways - this type of walkway is suspending with no post supporting. They depend on cantilever force of the lumber extending 3x the width of the walkway into the building. If the structural framing is damaged, the unit must be vacated to replace the damaged floor framing system. These are some of the most expensive walkways to repair.



Roof Top Decks - most commonly have living space directly below them. When the deck leaks, water enters the ceiling of the unit below. This type of waterproof deck can be repaired fairly easily. The repairs can be costly because the decks are commonly large ranging from 300 -600 square feet. Some rooftop decks are more than 1,000 square feet in size.



Balconies - Balconies can be cantilevered or supported by traditional framing methods. They are easy to fix but can be disruptive to the inhabitants because the materials must be brought in by the front door of the unit.


You Can't Go Wrong With AFP


To sum it all up, you can't go wrong with either the Flex-Dek or Flex-Dek PRO waterproofing systems from Advance Flooring Products. They are all excellent choices for waterproofing your balconies and decks. Even at a premium price point, these systems offer unsurpassed performance, benefits, and the best warranty in the industry.


The key to increasing a waterproof system’s lifespan is regular maintenance. Keeping the surface layer sealed is critical. Ultraviolet light is brutal and that exposure to the sun can cause fading to all system topcoats. I always encourage property owners and managers to establish a timely schedule and set a financial budget for yearly maintenance. Any damage caused by moving items over the surface should be promptly repaired to prevent water intrusion and prevent thousands in potential repairs.


For more information on AFP’s products, visit AFPFloors.us or call 707.742.5360

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