Kerdi Board vs. Kerdi Membrane: What the Difference Is and How To Use It

When tiling surfaces susceptible to wet conditions, such as shower tubs and bathroom floors, you will need a high-quality waterproof substrate. This part of your project is crucial since improper paneling can lead to mold/mildew, cracked surfaces, and other underlying issues.

That’s where Kerdi board vs. Kerdi membrane comes into play.

Both are excellent building materials, albeit they serve quite similar functions. They’re so alike that it can be hard to distinguish their exact differences. As a result, many people are confused about which option is better.

Well, we’re here to clarify for those of you who are confused. In this informative guide, we’ll outline the exact specifications of each lining, including what materials comprise them, their uses, and installation measures. 

Overview

Here are some of the key features of each substrate:

Kerdi Board

The Kerdi board is a versatile tile substrate primarily used to create a flat surface for your tiles. It is waterproof and comes in various lengths and widths, making it suitable for all project sizes. Additionally, it’s easy to handle, and you can cut through it with a simple utility knife.

Kerdi Membrane

The Kerdi membrane is the underlying tile panel that’s, like the Kerdi board, waterproof and quite pliable. One of the membrane’s main features is that it’s vapor retardant, making it ideal for surfaces that are exposed to moderate to heavy amounts of water regularly.

Materials

When comparing the Kerdi board vs. the Kerdi membrane, you first need to consider their materials. 

Kerdi Board Materials

Kerdi boards consist of extruded polystyrene, which forms a foam panel. Along the sides are reinforcement features. Additionally, there is fleece webbing designed to anchor into the thin-set mortar.

Kerdi Membrane Materials

Soft polyethylene makes up most of the Kerdi membrane. Both sides are covered in fleece webbing. Like in Kerdi boards, this webbing anchors the membrane to the thin-set mortar. 

How To Use Kerdi Board vs. Kerdi Membrane

The Kerdi board is more versatile than the Kerdi membrane, although the Kerdi membrane is better at repelling water. Learn more about the differences below.

Kerdi Board Functions

When paired with tile coverings, Kerdi boards can form bonded waterproofing assemblies. You can place these pairings in showers, platforms around bathtubs, countertops, vanities, shelves, and other areas that may become damp. 

You can install the Kerdi board on any structure or use it to create partitions, even if there is no structural support. 

For example, you can use tile and Kerdi board to build a shower or vanity in an empty room.

Kerdi Membrane Functions

Though the Kerdi board is advertised for a wider array of functions, it appears that the Kerdi membrane is superior in vapor management. 

Both may be waterproof and adequate at repelling water, but this is where the membrane excels.

As such, you’re more likely to use the Kerdi membrane for areas subject to heavy amounts of water and vapors, such as residential bathrooms, saunas, bathtub surroundings, and steam rooms.

That’s not to say you can’t use the Kerdi board for your bathrooms, but the Kerdi membrane is slightly better at preventing cracks and mold.

Installation

While the basic installment is identical, the Kerdi board has many more applications and, thus, more installment procedures than the Kerdi membrane.

Installing The Kerdi Membrane

Installing the Kerdi membrane is quite simple. 

Ensure that the surface is clean and free of contaminants that could compromise the binding material.

Next, apply a thin layer of mortar with a V-shaped trowel and work it in until it’s smoothly and evenly spread out on the surface. It should be free of air bubbles and pressed in tightly on the surface.

Press the Kerdi membrane onto your walls and let it set. Apply another thin layer of mortar in a similar fashion.

Afterward, your building material can be applied to the surface. 

For complete instructions, go to the Kerdi membrane official installation procedures.

Installing The Kerdi Board

The Kerdi board can be installed similarly to the Kerdi membrane or in an assortment of other ways, depending on your construction needs.

For example, it can be used on a wood or metal frame or as the basis for a countertop in your kitchen. Waterproofing measures are generally the same for each application.

You can find a complete list of installation instructions on the Kerdi board main page.

Maintenance

The Kerdi board and Kerdi membrane have the same minimalistic maintenance procedures. First, they must not be exposed to direct sunlight. These materials are generally for internal usage only, so external applications should be avoided.  

Otherwise, once you correctly implement them, there are no other upkeep or maintenance procedures you have to uphold. 

The Bottom Line: Which One Should You Use?

Whether you use the Kerdi board or the Kerdi membrane is contingent on what you’re trying to accomplish. 

If you’re focusing on projects that require more complex shapes and build paths, such as tables, countertops, and shelves, then you’re probably going to go with the Kerdi board. It’s much easier to cut up and was made for all types of projects.

On the other hand, if your goal is to line your shower with tiling or install ceramic walls in your bathroom, we recommend using the Kerdi membrane. True, you could use either in this instance, but why not go for the one that was made specifically for waterproofing your siding? 

FAQs

Here are some commonly asked questions around the web about Kerdi membrane and Kerdi boards:

Do you need a cement board with a Kerdi membrane?

As with most other substrates, a cement backer board is the best option for the Kerdi membrane. It’s not the only option available; however, it is the most optimal.

Should you install drywall before Kerdi boards?

Yes, you should 100 percent install drywall before Kerdi boards. This will prevent water from damaging the inner lining of your walls and create more structural integrity. Like the Kerdi membrane, a cement backer is the best material you can use.

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