If you are installing tiles in your bathroom, tub, or kitchen, you will need to waterproof the walls. As you may already know, tiles are not water-resistant and will let water seep through.
For an area that experiences a lot of exposure to moisture, waterproofing is crucial to ensure the structures behind do not get damaged by water and mold doesn’t develop.
Kerdi and DensShield are some of the most popular waterproofing products. They are often used separately. But you can also use them together with the help of an unmodified thinset.
DensShield has a thinset-friendly surface, making it possible for you to lay Kerdi over it. As long as you use thinset, Kerdi will adhere to DensShield without any issues.
What is Kerdi?
Even though Kerdi will stick to DensShield when you use unmodified thinset, it’s crucial to learn more about both products and if it’s recommendable to use them together.
Kerdi is a waterproofing and vapor retardant membrane made by one of the leading manufacturers of construction products, Schluter.
Kerdi comprises pliable sheets used as a waterproofing membrane over a wall. If correctly installed, the Kerdi membrane guarantees no penetration of water over it.
Because of its excellent waterproofing capabilities, Kerdi is used in bathtubs, showers, and kitchens. Kerdi can be tiled over, and that’s an added advantage.
There are plenty of benefits to using Kerdi. It prevents the growth of mold. It also has an anchoring fleece on both sides to help promote adhesion with thinset mortar.
Kerdi creates a uniform finish on a surface which is crucial for aesthetics and tiling. Finally, the sheets are available at 6’7′, which ensures easy and quick installation.
What is DensShield?
DensShield is the first tile backer board that comes with a moisture barrier. As a result, when installed, DensShield minimizes the amount of water absorbed compared to a typical cement board.
One of the perks of using DensShield is that it’s easier to install since it cuts as effortlessly as drywall. You won’t require any special tools or skills.
Because DensShield contains a built-in moisture barrier, it can be used in bathrooms, kitchens, and any areas that experience high humidity.
Like Kerdi sheets, it’s sold in convenient sizes, which speeds up the installation process. This tile backer board can be used on floors, ceilings, and roofs because it’s pretty strong.
Should You Use Kerdi Over DensShield?
From the above, we have seen that Kerdi is a waterproofing membrane, and DensShield is a tile backer board with a built-in vapor barrier.
If you are interested in using both, you need to know that you will have a double moisture barrier and what benefits will there be from such an outcome.
Both are waterproofing solutions that can be tiled on. If you are interested in preventing moisture from soaking past the tiles, you can achieve that with either Kerdi or DensShield.
Using both would be a waste of money, time, and resources. Even though Kerdi will work by sticking to DensShield, it’s generally not a good idea to use a double moisture barrier.
Does Schluter Recommend Using Kerdi Over DensShield?
When you inquire from the manufacturers of Kerdi, they will not advise you to use two moisture barriers. They will ask you to stick only to their products. That’s also the same advice you will get from manufacturers of DensShield.
Indeed, there won’t be any incompatibility issues between these two, but it doesn’t make sense to use a double moisture barrier, yet one of either will be enough.
Can You Use DensShield on the Walls and Kerdi on the Floor?
Laying Kerdi over DensShield differs from using DensShield on the walls and Kerdi on the floor. Sometimes, you may be forced into creating a hybrid vapor barrier in your bathroom.
The above is a perfect example whereby the pan is covered with Kerdi, and the walls have DensShield. For such an application, it would be easier to use Kerdi over the shower. But you may have your reasons.
It’s also possible to combine DensShield with Kerdi. In this scenario, the walls will benefit from the DensShield waterproofing barrier, and the water-resistant Kerdi will cover your pan. The problem will only arise at the seams.
To ensure the seams between Kerdi and DensShield are watertight, you should overlap the Kerdi onto the DensShield board.
Since these two are compatible as long as you use an unmodified thinset, the overlap will cure into a water-resistant seam. However, expect some build-up on the seams, which can make it hard to achieve a uniform surface when tiling.
Will Kerdi Work on DensShield Seams?
Yes, it will. A lot of shower installation jobs use Kerdi on the seams of DensShield. As long as you use thinset mortar to attach the Kerdi to the DensShield, it should hold up for a considerably long period. It should also prevent moisture from seeping through.
On seams, the best Kerdi product to use is the waterproofing strips. These perform an excellent job of sealing joints or corners that are difficult for you to waterproof using DensShield.
How Does Kerdi Compare to DensShield?
If you contemplate using Kerdi and DensShield together, it’s also essential to know how they compare against one another. This information will help you know whether there is a need for a double vapor barrier.
First, DensShield waterproof layer becomes compromised when you nail or screw over it. That requires you to cover the openings with a waterproof membrane such as Kerdi or RedGard.
On the other hand, Kerdi doesn’t require any fasteners. It’s installed directly over a wall and creates a waterproof membrane without you having to nail or screw anything. That means it doesn’t need any support. Place it on top, and you should have a waterproof layer.
But DensShield is a tile backer board that has an in-built vapor barrier. Kerdi is just a plain waterproofing membrane that has to be applied on top of a substrate such as a cement board.
When you use DensShield, you get a strong substrate for your tiles to adhere to. And with Kerdi, there is no need for fasteners which creates perforations that moisture can leak through.
Both Kerdi and DensShield have advantages and disadvantages. Using both isn’t a good idea. You should evaluate which option seems most suitable for your project and settle on that.
At the end of the day, whether you choose Kerdi or DensShield, you are assured of having a water-resistant surface.
Which Should Go First? (In case you decide to use them together)
Should you decide to use Kerdi and DensShield, you should know which one should go first. You would want to place the DensShield at the bottom of such a project.
Being a backer board, it is more resilient and will give Kerdi something to bond to. Once the DensShield boards are installed, you can follow up with a waterproofing membrane such as Kerdi.
Laying Kerdi is pretty easy. Use thinset mortar to lay the sheets on top. On the seams, you can lap them or cover butt joints with the Kerdi strip band.
Is Using Kerdi Over DensShield Expensive?
Yes, it’s costly. For a homeowner looking to keep the costs of their waterproofing project low, you should consider either Kerdi or DensShield.
Using Kerdi over DensShield is like installing a door over another door. Yes, you may create a fully waterproof surface. But you will still be okay with just one waterproofing product.
Will Kerdi Over DensShield Affect Tiling?
The good news about using Kerdi over DensShield is that this waterproofing membrane is also an excellent tiling surface. Once Kerdi cures on a surface, it can adhere exceptionally well to tiles.
So, you don’t have to worry about tiles falling off a Kerdi waterproofing sheet. What you should be worried about is the extra thickness. If you must use both Kerdi and DensShield, you need to have a lot of wiggle room.
The Kerdi will add a few inches to the DensShield layer. If you only use Kerdi on the seams or corners, you may not have a uniform surface to work with.
Getting an aesthetically pleasing finish on the seams can be tricky if you are not a tiling expert. The tiles may be crooked, and that’s a recipe for disaster. This is something you have to keep in mind.
Will Kerdi Waterproof DensShield?
Most people considering using Kerdi over DensShield are unfamiliar with one crucial detail: DensShield has a built-in vapor barrier. You may only consider using Kerdi to waterproof DensShield if you only assume it’s a plain tile backer board.
When you visit the official site of DensShield, you will see that they clearly state it contains a water barrier. Therefore, there is no need to waterproof it.
Unlike ordinary tile backer boards that absorb and let water pass through, DensShield is waterproof, and it will protect any materials beneath from water damage and mold.