Usually, when we are building a shower into a bathroom, we need to use a lot of products to complete the build: wallboard, tiles, shower benches, pipe seals, grout and caulk, just to name a few.
We can then combine these to create the shower, which (hopefully) has a watertight end finish.
While this approach can work, Schluter has conveniently taken all the components you need to make a genuinely waterproof shower environment and put them together as a single product called the Schluter shower system.
While many users are pleased with their Schluter System installation, a few issues have been reported which you should be aware of as a potential buyer.
Most Common Schluter Shower System Problems
This system is designed from the ground up to work together to create the most watertight shower installation possible.
This includes their KERDI bond and KERDI boards, which are completely waterproof and the KERDI drain and line products, ensuring all the plumping connections are secure.
Many people are pleased with their installation and swear by it as the most watertight shower pan installation they have ever used.
With that being said, in order for this system to work properly it needs to be installed correctly and this is where people run into problems with issues such as misaligning the studs or laying the kerdi bond too heavily, which causes a buildup in the corners.
Let’s go through all these installation errors people run into so you can be sure that yours is built correctly and will be as secure and reliable as possible.
Misaligned foam board studs
Schluter claims that their Kerdi board is better for mounting onto shower wall studs than more common boards, such as regular gypsum or backer boards, which need additional sealing to prevent water from returning.
While the Kerdi board certainly does a good job, it’s essential that you use the correct thickness of the board and that it’s correctly mounted to the studs.
For studs spaced at 16″ on center, you should use ½” (12.5mm) size board and for the larger 24″ spaced studs, you should use a thicker board at ¾” (19mm) to provide that extra rigidity due to less stud support.
When your stud spacing exceeds this requirement, you will need to place additional horizontal studs to use the correct attachment spacing.
In addition to that, you should use Kerdi’s screws and washers to ensure they make a solid connection.
Finally, you may wish to take additional steps and wet shim the kerdi board over the studs to provide as clean of a connection as possible.
The goal here is to create the flattest surface possible for tiling, including correct stud spacing and height, using the right thickness of the board and the right screws.
Not enough screws
A Schluter shower pan installation kit uses its proprietary screw type and washer, which is designed to give as solid of a connection as possible.
The number of screws you require to complete an installation can often be more than you expect.
Their kits only come with 40 screws and washers, so for larger installations, it’s possible to run out, at which point people will usually either be more liberal with their screw spacing to ‘make it work’ or use another type of screw so that they don’t need to go and buy more of Schluter’s own (and rather expensive) proprietary washers.
Don’t skimp here.
KERDI board is quite different from gypsum board and should be installed according to their specifications.
Consider purchasing a box of 100 screws and washers so you can be sure that you have enough.
Wrong trowel size
While we all might trust our skillset with a towel to not think using an improper size would affect the installation.
Still, because Schulter relies on a precise and correct application of kerdi bond to ensure a watertight fixture, it’s more important than ever that we use the right tools.
What commonly happens when the wrong tool is being you is the bond will build up in the corners, meaning the seams are not nice and flush, which results in gaps once tiled over.
Incorrectly mixed thin set mortar
Schluter boards have a unique waterproof resistant membrane that requires a unique mortar product to seal the seams and make things watertight.
This is called ‘Thin-set’ or ‘all-set’.
While they offer other products designed for faster setting times, we recommend sticking with the trusted thin-set mortar.
However, a common user error that occurs when using thin-set mortar is that an incorrect amount of water is used during mixing, which results in an uneven application and thus poor water sealing qualities.
Pay careful attention to the amount of water required, the thickness in which the mortar should be set and curing times to get the best possible results.
Still not completely waterproof (even after correct installation)
This problem comes down to the use of the kerdi membrane.
While by and large, these are great waterproof cement boards and any standard testing of their water-repelling qualities will yield good results.
The reality is when these boards are submerged for long periods (ie, continuous shower use from a large family), people have reported the system not being 100% waterproof, which, over time and with consistent exposure, can end up causing all kinds of problems such as mold growth, drywall bulge or other home damage.
Voids between the tiles and kerdi membrane
If you don’t keep a solid connection when installing the waterproofing system and ‘spot bond’ the tiles to the boards, voids can appear where water can collect, which over time will weaken the tiles’ bond to the wall.
Grout issues
If gaps between the boards or the edges are not correctly sealed up, any grout that sits over them will have a hard time staying in place.
Over time it may crack and break away.
Ensure all grout is backed up correctly by boards to ensure good adhesion.
How to fix Schluter shower system problems
The common theme here is that most issues you will run into with the Schluter Shower System are fundamentally caused by installation errors.
Here’s a rundown of essential things to keep in mind during your installation so you can ensure everything is as tight as possible and performs flawlessly.
1. Ensure mounting instructions are adhered to
The first step to a perfect Werner schlüter Shower system installation is to ensure you use the correct cement board thickness based on your shower wall stud spacing.
And to use any additional horizontal support where needed (for example, when the studs are too far apart).
2. Use Schluter’s own screws and washers
These screws and washers are designed to work specifically for the KERDI board.
Both the length of the screw and how the washer adheres to the board are very important.
Make sure you’re stocked up on them, so you don’t have to substitute screws for another brand.
3. Use a good trowel
The recommended tool for applying the mortar correctly is a U-notch or ¼ by ⅜ inch square trowel.
Use this tool for the best mortar seal and water resistance possible.
4. Mix the thin-set mortar correctly
When mixing the mortar, be sure to follow the instructions detailed on the packet as closely as possible.
There are also guides online and on the official Werner Schlüter YouTube channel which will help with applying the mortar correctly.
5. Take care when submerging boards
While KERDI boards have excellent water-resisting properties, when subjected to water submersion for a prolonged period it’s still possible for water to damage the Schluter system.
Be mindful of extended or sequential shower use and give the shower some time to dry out.
6. Ensure good tile adhesion
Spot tile adhesion tends to leave voids between the boards and tiles which can accumulate water.
Ensure the tiles are solid and adhered to the board and there are no possible gaps for water to get through.
7. Secure grout
Grout must always have backing behind it; if there are gaps between the boards or drywall seam where the grout is unsupported, it will inevitably weaken and eventually break away.
Make sure all grouting has a surface behind it to adhere to and create that super secure connection needed for a waterproof shower.
Paul Wilson is a highly skilled plumber with over ten years of experience in the industry. He holds an IDPH license and takes pride in his ability to tackle many plumbing issues and successfully complete even the most challenging projects.
