Water can find the smallest space in a bathtub or shower space and create a big stinky problem over time. Unfortunately we’ve been the recipient of many aspirins because of water leaks not only in our own houses but in multiple rental homes.
But it doesn’t have to be this way, especially if you’re thinking of remodeling your bathroom.
If you’ve been reading our blog you know that we’ve been helping my brother-in-law install a new bathroom. He decided to completely remove the existing blue bathtub (this blue must have been a popular color in 1975!) in favor of a tiled space.
The last post we put up about this project dealt with how we installed cement board. Today we’re going to share how we made the cement panels completely waterproof using RedGard (1 gallon costs $50). We’ve discussed this product before because it prevents water from seeping into walls & serves as a crack prevention membrane for the tiles adhered on top of it.
We’re sharing our experience so that either you can waterproof your cement board or instruct your contractor to do what we did. Like we’ve said before, even if you don’t do this type of work it’s always a good idea to familiarize yourself with the process so that you know a good job is being performed on your behalf. Being your own advocate is a smart thing in any endeavor and especially so in home remodeling 🙂
We know this post will guide your bathroom renovation project in the right direction. If at any point you have a question or tip of your own, please type it in the comment section below. We love hearing about your projects!
Table of Contents
Add Cement Board Tape to All Seams
The last few posts about this bathroom remodeling project discussed hanging cement boards to the bathtub wood studs. Cement board is the cheapest backer board for showers.
We also like Wedi and KERDI-BOARD because they’re faster to install. Whether you’re doing a small bathroom remodel or a large project, the tips in this tutorial are great.
Adding self-adhesive alkali-resistant fiberglass tape to all the cement board seams is a really important step. This tape needs to be applied to every area where the cement board panels butt against each other or other sections of drywall/plaster.
We added tape to all the seams and then used a thin layer of thin-set to embed it onto the cement board.
The thin-set was the same kind used to adhere the tiles to the cement board panels and the consistency should allow it to just barely hang off a margin trowel or putty knife.
Smooth out the thin-set before it dries. We used a drywall sanding sponge to feather the thin-set because any ridges or bumps will cause the tile to lay unevenly. Use a level to check and fix any peaks or valleys.
We also applied a thin layer of thin-set to all the screw heads in the cement board. By the time you’re done with doing all this your bathtub space will look like the following picture.
The thin-set will need to dry for about a day. Once it’s rock solid take a level and make sure all areas where the tile will be placed on the cement board don’t have any peaks or valleys.
This is especially true at the seams between two cement board panels or a cement board panel and existing drywall.
If you encounter a peak/valley problem between cement boards and drywalluse lightweight setting-type joint compound to level the transition.
If you have a peak/valley issue within the cement board field use thin-set mortar to level the area.
On this project it took a few passes with both joint compound and thin-set to get the cement board area suitable for tile.
Prep Work for RedGard
The prep work for RedGard is straightforward. Since it does have a thick texture, RedGard should be applied only on the areas where there will be tile. Hydro Ban is also another option to waterproof cement board.
Otherwise, the paint job of the adjacent wall next to the tile will look less than crappy (and we mean this in the nicest sense). You can either snap chalk lines or use a pencil & level to mark the area where the tiles will go.
Don’t get RedGard on the tub. We used blue tape along the edge of the tub where it met up with a cement board.
Then, we placed a piece of cardboard on top of the tub to further protect it from any drips.
The last step for RedGard prep is to dampen the area where it will be applied. We used a bucket of water and a sponge. Take special care to get the corners of the cement board damp as this is the location where you want the RedGard to really adhere.
Now the RedGard is ready to be applied. It’s actually a pretty fun process, but make sure to wear a respirator because it is stinky stuff.
RedGard Creates a Waterproof and Crack Resistant Membrane
Applying RedGard to any surface is super easy. If you can paint a wall you can use RedGard no problem. And for this shower, we only needed one gallon.
There are two ways to get RedGardon cement board panels:
- Roll it on the wall with a 3/4 inch nap roller
- Trowel it on the wall
In this bathtub example, we rolled the RedGard onto the cement panels using a Purdy brand 3/4 inch roller.
Use a good roller that won’t shed too much lint into the RedGard. Otherwise, you’ll have red boogers to remove from the wall.
The first application was put on vertically.
Use a paintbrush for areas that are unreachable with the roller. We paid close attention to applying a good coat of RedGard to all the corners and spaces adjacent to the tub since these are the areas that water likes to penetrate the most.
Let this first coat of RedGard dry until the panels appear red in color. This took about 1 to 1.5 hours.
Drying time depends mostly on temperature & humidity levels and the surface will appear pink until the RedGard has completely dried.
When the RedGard appeared red and wasn’t tacky we applied a second coat horizontal to the first. Again, as you roll it on the walls check to make sure there are no bumps or small lint boogers in the coating.
The end result should be a bathtub surround that is red in color.
The bathtub walls are now completely waterproof and the RedGard also serves as a crack isolation membrane. This means RedGard will expand and contract ever so slightly to prevent cracks from forming in the shower tile.
Keep in mind, the thickness of RedGard should factor into how far to set a shower valve like Moen’s Posi-Temp or Hansgrohe’s iBox.
What’s Next
There are many ways to waterproof a shower, so pick the one that works best for you.
If you’re doing a bathroom remodel and need help, join one of our online courses – they’ll make your bathroom renovation much easier!
Let me know if you have any questions and I’ll do my best to help.
Cheers,
Jeff
RedGard Waterproofing
