How To Waterproof A Shower Before Tile Installation

Waterproofing shower walls is the project we did the most extensive research on when it came to our primary bathroom renovation. Waterproofing before tiling a shower is so important and can protect your bathroom for the long haul. So learning how to waterproof a tile shower was top on the priority list for this DIY bathroom remodel.

How to waterproof a tile shower using RedGard liquid membranes, installing white subway tile on top of waterproofing

Building Codes For Waterproofing A Shower

Before diving into today’s post, a quick word of caution when it comes to waterproofing a shower, or bathroom renovations in general. Make sure to do your research and check with your local code enforcement office as every municipality is different. Pull those permits and get your projects signed off on.

Our situation here in rural Vermont is extremely strange. When we went to renovate our first bathroom here, we searched the town’s website about residential building codes and found nothing. We contacted the town to inquire about it since we were used to working with the town code office when we lived in Maine. They responded that most single-family, residential buildings in much of Vermont are not regulated. It’s the wild west and buyer beware here. Comforting, right?!

Technically, we can do whatever we want to this home. Does that mean we’re going to cut corners? Absolutely not. We love this home and have a passion for quality, well-researched, DIY work that will stand the test of time.

While at first we cheered “Yay no codes to decipher and no inspections,” we realize it isn’t great. The biggest drawback in my opinion and for us as DIYers, is not having a set of guidelines or a person we can rely on to steer us in the right direction. Deciphering and interpreting building codes is hard! It’s handy to have a code inspector come by and say, “Nope, you did this wrong, fix that and you’ll pass inspection.”

So all of that to say don’t take our method of waterproofing a shower as the way to do it. There are different methods to get a waterproof layer for your tile shower. Do your research and make sure you’re doing it according to your local code specifications. Our method is based on the research we did and what we are comfortable with.

Applying RedGard liquid waterproofing membranes to shower walls using a paint roller, goes on pink but dries red

How We Waterproofed Our Last Shower

Looking back on our guest bathroom remodel, I felt like we could have waterproofed our shower better. At the time, after doing research and based on some old codes from when we lived in Maine, we opted to install a water vapor barrier behind the cement board, seal the cement board joints, tile directly on top of the cement board, seal the gap between the tub and tiled walls with waterproof silicone, and apply waterproofing over the entire shower (tiles and grout joints both) using a waterproof sealant.

Technically, it was waterproofed. And we do re-waterproof the tile and the grout every year, which honestly is kind of a pain but it’s what we do to avoid mold growth issues. It’s been almost ten years since that bathroom remodel and we haven’t had any issues with water damage, moisture problems, mold, or mildew growth.

Liquid Membranes

There are a few shower waterproofing options, but the method we landed on for waterproofing our shower walls was using liquid membranes. This waterproof membrane is painted onto the cement board and acts almost like waterproof paint underneath your tiles. The product we chose was RedGard, which is one of the most popular liquid waterproofing membranes on the market and was readily available at our local Home Depot and hardware store.

A one-gallon bucket of RedGard Waterproof Membrane

We still installed a vapor barrier behind the cement board, but adding this extra waterproofing layer to our new shower space gave us the peace of mind that we wouldn’t have unseen moisture issues. The RedGard liquid membrane material was applied to all the wet areas, like the shower or any spot with excess moisture, to provide that extra barrier of protection.

Waterproofing Shower Walls: How To

Let me walk you through the entire step-by-step process for installing this liquid, waterproof shower membrane and prepping our shower walls for ceramic tile. This tutorial starts with having the cement backer board up and installed.

Supplies For Waterproofing A Shower

Tools For Waterproofing A Shower

Install Seam Tape

The first step is taping all the cement board seams with 2″ mesh tape that’s meant for tiling. Make sure that it is alkali-resistant and moisture-resistant.

A roll of cement board seam tape

Basically, anyplace where the cement boards joined together, got taped. Both the flat joints and the corner joints. 

What does seam tape to? It helps create a more solid surface to support tile and prevent flexing. When you don’t use seam tape, you could potentially have problems with cracked walls.

Seam tape on cement board joints to prep for tiling

You want to try and get the seam tape nice and flat, centered over the seam, and sealed down. There were a few instances where, when working with big strips in particular, the seam tape wasn’t quite centered we had to go back through and fix it.

Apply Thinset Mortar

With all the joints taped, it’s time to secure them with a layer of thin-set mortar. This step is kind of like mudding drywall joints if you’ve ever done that. Mix up your mortar base, then use a putty knife (I liked using a small, 3″ putty knife), carefully apply the mortar over all the taped seams and the screw heads. You don’t want to see any holes or gaps.

Applying thinset mortar to cement board joints using a putty knife

Be super careful in the corners not to rip the mesh tape but also cover all the gaps. Smooth out the seams and avoid chunks or drips that could be problematic when you start installing the wall tile.

A Hawk Is A Helpful Tool

This is a task where a hawk can be super helpful. It’s not necessary, but it helps hold the thinset while you work and keeps you more mobile. It holds small amounts of mortar with you instead of repeatedly going back to your bucket. I also prefer it because it’s easier to keep my putty knife clean and drip-free, scraping it along the edge of the hawk before reloading with mortar.

Using a hawk and a small putty knife to apply thinset mortar to cement board joints in a bathroom renovation

Which Thinset Mortar To Use?

We tried a few different thinset mortars for this project since there was no shortage of wall tiles to experiment with. Our favorite was the VersaBond thinset mortar which costs $18 for a 50 lb bag at Home Depot. It dried quickly, but not too quickly, was fairly easy to mix, highly rated for wet areas, and durable.

VersaBond thinset mortar 50 lb bag

Mixing Thinset Mortar

It took us a while to figure out how to mix small quantities of the thinset mortar, especially when we just needed a little bit at a time to mud all the joints. We found a great thinset mortar mixing guide on the DIY Tile Guy website. The guide spelled out different mixing ratios by thinset mortar brands. Every brand is different! You do have to subscribe to a mailing list to see the chart, but it is worth it! VersaBond is included on the chart and our mixtures turned out perfectly every time.

After letting the mudded seams and joints dry for at least 24 hours, it’s time to move on to applying the waterproof membrane.

Research Waterproofing Method

Now for the fun part, researching application techniques and applying the liquid waterproofing membrane to your shower walls.

While letting everything dry for a few days I went to town googling “how to waterproof shower walls” and “how to waterproof a tile shower” obsessively. YouTube was a treasure trove of waterproofing videos from professional tilers that were super helpful.

A few things were consistent across all the videos and here are the top tips I gathered for applying RedGard and waterproofing shower walls. One, the stuff is a chemical, a strong chemical and while not a requirement to wear the proper safety equipment, you definitely should. Two, it’s hard to clean up and doesn’t clean up easily. Using a disposable paintbrush along with a paint roller cover and tray liner you can throw away is helpful. And three, you need to apply at least two coats to get proper coverage and you must ensure there are no pinprick holes to ensure the walls are water resistant.

RedGard application supplies including a paint tray liner, cheap paintbrush, and a paint roller

Apply Liquid Waterproofing Membranes

Once I felt comfortable, gathered my supplies, covered the tub in plastic (because hashtag messy), and found a chunk of time without the kids around, I cracked the one-gallon tub of RedGard and got to work.

Protecting the bathtub with plastic in preparation for applying RedGard waterproofing membrane and beginning tiling the shower surround

The stuff is like slime. Stinky, thick, pink slime. I now understood why I saw so many pro tilers just dunking their paint roller directly into the giant, three-gallon bucket of RedGard that they had! It was comical to dump a glob of RedGard into the paint tray. But we only needed a smaller, one-gallon container for our job so a roller wouldn’t fit in it.

RedGard liquid waterproofing membranes starts off pink and dries to red, it's like pink slime in the bucket

I started by rolling the walls with the RedGard then painting the corners and some of the edges that would be hard to reach with the roller. RedGard goes on pink and turns red when it’s dry. By the time I finished the first coat, sections were already dry. So I wrapped my brush, roller, and tray in plastic wrap to stay wet for a few hours while I let it dry completely before coming back for coat number two.

Applying RedGard liquid waterproofing membranes to shower walls using a paint roller, goes on pink but dries red

Apply A Second Coat Of Waterproofing Membranes

It took a couple of hours for the first coat to dry completely. Once it was all dry, I repeated the RedGard painting process for a second coat. The second coat took a whole lot longer to dry. I let it dry for 24 hours. In the meantime, I tossed my brush, roller cover, and paint tray liner.

Inspect The Waterproofing Layer

The next day I inspected the walls for any holes. The surface was wild! It felt like textured rubber which I guess is the point of a liquid-applied membrane, huh?! The last thing I did for this waterproofing method was to spot-paint RedGard on any areas that showed pinprick holes. The goal is to achieve a solid, waterproof surface to prevent water penetration or water seepage to the cement board below.

To inspect the RedGard application, you had to get up close and personal to find the holes. I found quite a few which I suspected was because I didn’t use a very textured paint roller. We didn’t have a rough roller in our paint supply bin and I preferred to use an old one rather than buy a new one and throw it away.

I ended up spending quite a bit of time inspecting the walls and painting over any holes. In retrospect, I wish I either did a third coat of RedGard or used a rough textured roller.

Inspecting a shower wall after RedGard application to look for pinprick holes

Follow The Manufacturer’s Instructions

There are different liquid membrane products for waterproofing bathroom walls. Different products do have different instructions. So word of advice to make sure you read ALL that fine print on the product you choose to get great results with your bathroom waterproofing. I know it’s a pain, I know the writing is super small, but break out those readers and make sure that the bathroom waterproofing project is done right.

Thoughts On Waterproofing With RedGard

I can honestly say that I was completely intimidated by the waterproofing process. But that’s pretty common when learning a new skill or trying something new. For me, the more research I do and the more YouTube videos I consume from reputable sources, the better I feel about tackling something new and feeling confident about it.

Is waterproofing hard work? No, not really. It is time-consuming and boy, does it stink! But it’s something that I feel even a novice DIYer could tackle. In the words of the Beastie Boys just take it “slow and low” and you’ll be fine.

Is using RedGard the best solution for waterproofing a shower? I’m not sure anyone can say for certain, “this is the best way” but it is a popular method and a well-accepted way to waterproof cement board for a tile shower.

How Much RedGard Do I Need?

RedGard comes in two sizes, a 1-gallon container and a 3-1/2 gallon container. For most homeowner and DIY shower waterproofing projects, the 1-gallon container will be enough.

We applied two coats of the waterproof shower membrane over the cement board in our shower area and went through about 3/4 of the product in the one-gallon bucket. It was plenty for our needs and we have some left over.

The RedGard product coverage chart does show that one gallon will cover 55 sq ft. as a waterproof membrane. This checks out for us since the square footage of the wet area we applied the waterproofing layer to was 36 sq ft.

Tiling over RedGard waterproofing using a dark gray thinset mortar and white subway tile

How Much Does Waterproofing A Shower Cost?

It cost us $88 to waterproof our shower using RedGard. The most expensive part is the RedGard itself which cost us $80 at Home Depot.

The other materials I picked up for this project were seam tape for $8, a paint tray liner for $2, and two cheap paint brushes I could throw away for $6. I typically hate buying things like this to just use once and toss, but I also knew using my super nice and expensive paintbrushes wasn’t an option because I didn’t want to ruin them.

I had some rubber gloves I could wear and an old, roller cover I didn’t mind sacrificing to the job.

To estimate the cost of waterproofing, I didn’t include the cost of the thinset mortar. I would factor this in more with tiling cost since you don’t use that much of it to seal all the seams and the screw heads. That cost makes more sense paired with the tiling job.

Learning New Skills

Hold on for one moment while I was poetic about learning new skills, like for me, how to waterproof a tile shower. Sometimes I feel stuck in my ways or stuck in a rut and learning new skills helps pull me out of that rut. This project was fun to research and try out for the first time, helping build more DIY confidence. Every new skill I gain helps me tackle the next project or new task with a little more ease and assuredness.

I’m so glad we found the right waterproofing method for our bathroom renovation project and added this skill to our DIY repertoire. It gives us peace of mind, especially after the unbelievable amount of time we put into tiling our bathroom, that we did it in a way that will hopefully last our lifetime here.

2 Comments

  1. thanks for your post!! my goal is to have smooth shower walls with NO tile. I would use the cement board then some kind of waterproofing like the redgard and then? i’ve read folks using pool paint to seal it, but it doesnt look like from your photos that the surface would have a finished look after just the redgard. thoughts? thanks!

    1. No, I don’t think RedGard would give you the smooth look you’re going for. Granted, we used a textured roller to apply it with, but it’s still a very messy uneven material to work with. Pool paint sounds like a good idea. Good luck with your project!

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