The Best Waterproofing System 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 five (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 give you an honest review of products from Life Specialty Coatings of Los Angeles, CA, and why you should consider their products for your decking project.

The Best Waterproofing Systems

WATERPROOFING AMAC Deck System

(AMAC System - a premium waterproofing product)

This AMAC Waterproofing System by Life Specialty Coatings combined an acrylic fiber lath, with its superior resin base and concrete modifier. This system represents 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 AMAC waterproof system including the lath, base coat, fiberglass mesh, first coat slurry, second coat slurry, 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 warranties the system for 20 years if the decorative coat is maintained.

(AMAC demonstration by Life Specialty Coating)

The AMAC 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 AMAC 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 repairs.

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 10-year plus 10-year warranty (or what they call a "Five + Five" Warranty) if the deck surface is re-painted with Life System paint every 5 years.

(Notice the 5-layers on this AMAC mock-up)

The image above is a mock-up of the AMAC system we trained on at a Life Specialty Coating certification course. 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. 

WATERPROOFING FM and MC Deck System

(The FM System uses a 4-layer system)

The FM Waterproof decking system is a cost-effective yet durable all-acrylic waterproofing system. It utilizes a fiberglass mat with an acrylic coating applied in steps for maximum performance.

This FM system is perfect for site conditions where a flexible waterproof membrane is required. As you can see in the image below, this product offers tremendous flexibility.

This picture below was taken at a product demonstration event and it shows the FM system installed on a piece of melamine board and then being flexed. Life System FM is less expensive to install because it offers fewer steps and materials.

(Notice the flexibility of the FM System - despite a 4 layer installation)

This system is less susceptible to cracking because the product offers 6,000 PSI of force resistance. It remains flexible and will not get crystalized and brittle.

This system can be installed over a surface that is stable and has been properly prepared. The manufacturer recommends this product for low pedestrian-traffic areas like balconies, and rooftop decks.

Additionally, Life Specialty Coatings offers a 5-year manufacturer's warranty if the surface is properly maintained. We highly recommend the FM system because it is easy to install, easy to repair, and easy to maintain. 

(Our team installing MC System in Redondo Beach, CA)

The MC Waterproof decking system is a fiber-reinforced system using water-based acrylic sealants. This system also uses a fiber mesh to further increase its overall strength.

One of the biggest benefits offered by the MC system is that it can be installed directly over existing concrete surfaces when using an epoxy primer. Benefiting from a total of 4 layers, the MC system is ideal for areas with heavy foot traffic like walkways, corridors, exterior stairs & landings.

A very versatile system, it can be used in both residential and commercial applications, in fact, it is frequently used in hotels and office buildings. In the picture above you can see one of our pros installing the first layer of modified slurry coat, directly above the fiber mesh that had been previously epoxy primed.

If your balcony has developed small cracks and has no major damage, the MC system is the best solution for your project. 

What is a Balcony, Deck, or Walkway?

(This is the typical balcony found in the South Bay)

The Los Angeles housing boom of the 1950s and 60s was heavily influenced by Tiki architecture that incorporates balconies, decks, and open walkways.

This is especially true in multifamily apartment buildings, a common sight in the San Fernando Valley. You can also find balconies and decks in Single-Family homes and large condo complexes built in the 1960s and 70s.

Many of these structures are made of wood (or wood-framed). But wood has one weakness, water. Continuous exposure to water can cause wood to rot, grow mold, and decompose. This is exactly why balconies and decks need to be protected (waterproofed) against moisture and water.

A balcony or deck layer consists of the wood frame, covered by a wood subfloor (typically plywood), a metal flashing or drip edge is applied, followed by a diamond metal lathe, a base coat of lightweight concrete, a base of slurry, a second coat of slurry, and a final decorative layer.

All of these layers work together to keep water and moisture out to protect the wood frame underneath.

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.

(An exterior cantilevered walkway or "catwalk" in Los Angeles, CA)

Cantilever Walkways - this type of walkway is suspended with no post supporting it. They depend on the 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.

(Rooftop decks are quite common in the South Bay)

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.

(Enjoy the outdoors from the comfort of your home)

Balconies - or “Lani” as they are called in Hawaii. 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

To sum it all up, you can't go wrong with either the AMAC, FM, or MC waterproofing systems from Life Specialty Coatings. They are all excellent choices for waterproofing your balconies and decks. Even at a premium price point, these systems offer unsurpassed performance and benefits. 

The key in 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.

Want to Learn More?

You can learn even more about balconies, decks, waterproofing, and resurfacing by reading these articles. Our blog has hundreds of articles to help you learn about remodeling and home improvement. 

• Everything You Need to Know About Waterproof Balcony & Deck Repairs
• Balcony Inspection Laws: What is SB326 & SB721?
• Waterproofing Services That Really Work