One of the least glamorous parts of building a good tile shower happens before any tile goes on the wall.
The walls have to be flat and plumb.
That sounds simple until you open up an existing bathroom and discover that the framing has its own ideas. Studs can be bowed, twisted, pushed in, or sticking out. If we simply fasten tile backer board to whatever framing is there, all of those imperfections can show up in the finished tile.
That’s where methods like shimming—and wet shimming—come into the conversation.
In the video Rob is reacting to, the installer prefers a manufactured shim system and isn’t a big fan of wet shimming. His concerns are fair: it can be messy, and traditionally you may need to wait for the mortar behind the board to firm up before fully fastening everything.
Rob’s take is a little different.
Wet shimming can still be a very practical solution, especially if you adjust the process.
First, What Is Wet Shimming?
Wet shimming is a way to correct uneven framing while installing a foam tile backer board.
Instead of attaching the board directly against a stud that isn’t perfectly straight, mortar is placed between the framing and the back of the board. The board can then be pressed into position while a level is used to get the wall flat and plumb.
Once the mortar firms up, the board is secured according to the waterproofing system manufacturer’s requirements.
In simple terms, the mortar fills the inconsistencies behind the board.
The result is a much straighter surface for tile.
Why Not Just Follow the Crooked Wall?
Because large-format tile has very little patience for bad walls.
When a wall bows in and out, the installer has to fight that problem while setting every row of tile. You may end up using excessive mortar to compensate, struggling with lippage, or creating cuts that change size as they move up the wall.
It is much easier to solve the problem before the tile installation starts.
A straight wall gives us better corners, cleaner grout joints, easier niche details, and a more predictable tile layout.
Preparation may not be the part homeowners photograph when the project is finished, but it has a lot to do with why the finished shower looks good.
The Main Complaint: You Have to Wait
The installer in the original video points out one legitimate downside of wet shimming.
With standard mortar, you can’t necessarily position the board and immediately tighten every fastener. Doing that could pull the board back toward the uneven framing you were trying to correct.
So traditionally, you position the board, allow the mortar to cure, and come back later.
On a busy jobsite, that waiting period can make the method feel inefficient.
That’s the part Rob thinks can be handled differently.
Rapid-Setting Mortar Changes the Workflow
Instead of using a mortar that requires a long wait, Rob suggests using an appropriate rapid-setting mortar when the system and application allow it.
Get the board where you want it.
Check it with the level.
Push it into position until the wall is flat and plumb.
Then let it sit.
With a faster-curing product, that may mean roughly an hour rather than losing most of the day.
And you don’t have to stand there watching mortar dry.
There is always something else to do on a bathroom remodel.
Cut waterproofing banding. Organize materials. Prep another wall. Clean tools. Work on another part of the shower.
By the time those tasks are finished, you can return to the board and continue.
Suddenly, the “waiting” part of wet shimming isn’t such a big disadvantage.
Shims Are Still a Good Option
None of this means manufactured shims are wrong.
Shims can be a very clean and repeatable way to straighten framing. If the studs are consistently out of plane, a good shim system can make it easy to establish a flat surface.
Traditional carpentry methods work too. Depending on the situation, framing can sometimes be sistered, furred, or corrected before the wallboard is installed.
There isn’t one method that has to win every time.
The important part is the result:
We want a flat, plumb wall before we start setting tile.
Waterproofing Still Has to Be Done Correctly
At MannTile, we prefer Schluter waterproofing systems, including surface-applied waterproofing that keeps the waterproof layer directly behind the tile.
But even a great waterproofing system benefits from good preparation.
Getting the backer board straight first makes everything that follows easier—from waterproofing the seams to setting the tile and finishing the corners.
Whatever method is used to correct the framing also needs to follow the backer-board and waterproofing manufacturer’s installation requirements.
We’re not improvising the shower assembly. We’re simply choosing the best approved way to get the wall where it needs to be.
Sometimes the “Slow” Method Isn’t Actually Slower
That’s probably the biggest takeaway from this video.
Wet shimming can look inefficient if you picture installing a board and then doing nothing while it cures.
But that’s not how a well-organized job has to work.
Use the right materials, get the wall plumb, move on to another task, and come back when the mortar is ready.
If that gives us a straighter wall and a better tile installation, the extra step is worth considering.
Thank you for reading!
Interested in learning more about plumb walls? check out this article!