Waterproofing: What It Is, and Why We Recommend It During Cladding Installation

The damage that water can wreak on your home or commercial property can be mitigated by modern cladding solutions that are effectively waterproofed during installation. Water should be on every property owner’s mind, as the mass of snow we have accumulated this winter starts to melt, and sleet and rain falls from the sky.

If you have chosen a modern material to clad your building, you already have taken steps to protect it from the elements. Waterproofing cladding is the final step to suring up its defenses against water damage. Here are the reasons why we recommend waterproofing during cladding installation, and how it is most commonly done.

Why Waterproof?

For the most common modern cladding materials, such as Aluminum Composite Material (ACM), Aluminum Siding, and High Pressure Laminate (HPL), waterproofing is optional, but highly recommended during the installation phase of your cladding project.

Why Waterproof?

The most popular materials for modern facades are on their own weatherproof, but by nature they are installed in panels that leave small gaps between them. These slight canyons may seem marginal, but they are significant enough to allow rain behind the paneling, which leaves the base wall–often composed of rot prone materials such as wood–vulnerable to water damage.

When thinking about waterproofing, we have a tendency to focus our thoughts, efforts, and resources on roofing, as we typically consider rain falling vertically. This is important, but it is critical not to neglect a building’s siding.

More often than not, the rain arrives with strong winds, causing the walls of your home or commercial property to bear the brunt of the precipitation. It is important to note that there is no silver bullet when it comes to rain and its impact.

Keeping building’s dry is a continued effort, at least until John Fogerty finally figures out “Who’ll Stop the Rain.” That said, careful installation of modern cladding–paired with proper waterproofing techniques–can abate the risk that water poses to your building or home.

Why Waterproof?


Air Vapor Barrier

Waterproofing your next cladding project should begin before the paneling is installed on the building’s exterior. An Air Vapor Barrier (AVB), often called “blueskin” after a popular version of the product, is central to the waterproofing process.

AVB is a compound of rubber and asphalt that is laminated and adhesive so it can be wrapped around the base wall of your building. As the name would suggest, this grants the base wall a skin that is water, air, and vapor tight.

When waterproofing, the slightest error can lead to a small ocean of trouble down the line, so AVB must be installed carefully. To account for this, AVB is designed to be forgiving to installers.

It is malleable to the curves and contortions a building might take, and is adhesive to the most commonly found materials in base walls, such as concrete and aluminum. Should self-tapping screws be needed to further fasten the barrier to the wall, AVB’s skin will seal around it.

AVB is considered a dry joint solution to waterproofing, and is highly recommended for working with ACM, HPL, or similar rainscreen cladding methods. Having AVB membrane wrapped across your base wall grants peace of mind when rain is shooting into the reveals between cladding panels.

One of the best traits of a material such as ACM is the way that its panels form a neat puzzle around your building. The reveals from one piece to the next add depth, texture, and shadowed accents to the look of the facade.

AVB waterproofing allows us to lean into this feature by leaving these reveals free, while still providing for a facade that will limit water damage to the building.



One method installers use for waterproofing is flashing. This is a common solution for ensuring that water is kept out of exterior points of entry such as windows, doors, and ventilation. Flashing involves fashioning metal into runways that will catch water over vulnerable areas of siding, and direct it away from such points.

Flashing is a centuries-old and ingeniously conceived process. At a time before modern materials, builders had to use structure in order to mitigate water, using careful angling to allow their projects to shrug off rain. These processes carry over today, as modern cladding solutions, weatherproof in their own right, sure up their defense of weak spots by way of flashing.

The benefit of flashing is greatly seen in the use of cladding constructed with Aluminum Siding. Aluminum is a common material used for creating flashing, pairing this waterproofing well with siding made from the same metal.

Done skillfully, end users to a commercial property or homeowners will think of exterior aluminum flashing as a design feature, an accent over windows and doorways that compliments the glossy look of the building’s facade.

When rain hits your building, you do not want it hanging around long. Flashing pushes water off and away from the facade, and is a great method for waterproofing modern cladding.

Caulking Cladding Panels

As mentioned, modern cladding solutions are often installed in panels that leave slight reveals between them. We spoke about dry joint waterproofing earlier, but another solution to suring up these openings is wet joint sealing.

Wet joint waterproofing, especially for ACM panels, is often done using caulk. Of the many caulking options, silicone is recommended for application with building siding.

Silicone has a reputation for resisting mildew and has a notable strength against distortion that can occur when the metal it seals expands slightly in hot weather. Caulk is dispensed quickly and easily with the use of a caulking gun, and the material is malleable to small corrections and adjustments before it sets and dries.

Skilled installers will run a thin spatula down the groove of the caulk, creating a concave that looks great, while allowing for water to run smoothly down the building. To save on materials where the gaps run deep, installers put a backing rod in the reveals before caulking the cavern.

For laymen, the backing rod is typically a foam rope that can be manipulated to fit in these gaps between paneling.

Caulk is modern cladding’s friend, and works in synergy with the already weatherproof nature of ACM. Like the cladding solutions that it is wrapped around, Caulk does not just repel water. It also adds to the heat insulation and noise dampening of your home or commercial property.


As spring nears, we all know the importance of waterproofing our buildings. Modern Cladding solutions, such as ACM, HPL, and Aluminum Siding, are renowned for their weatherproof composition, but that alone is not enough to be fully protected.

Maximizing the protection of a building’s cladding means waterproofing during the installation process. 

From caulking to flashing, contemporary installers of modern cladding know all the tricks for getting the job done right. Waterproofing can be a finicky process, and correcting work done poorly ranges from nuisance to catastrophe.

Wiedehopf has partnerships with some of the most skilled installers in the business, and we want you to get the most out of your modern cladding by ensuring that the waterproofing process is done well, the first time.

While we trade our parkas for rain jackets and head into march, we will stay on the topic of precipitation. In our next article, we will discuss rain-screen cladding, what it is, and how it can protect your building further. In the meantime, stay dry out there!

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