ONE ROOM CHALLENGE

Shower Waterproofing: Week 3 Fall 2021 ORC

You really shouldn’t tile onto drywall in a shower or a bathtub. It probably won’t last through one week of use. The walls need to be waterproofed. There’s several different methods for waterproofing that you can choose from, but not all of them are as diy friendly as the Kerdi shower proofing system made by Schluter.

The first method Mike and I ever diy’d was in our last house. We used a combination of Durock and Red Guard. Durock is cement board. It comes in 3’x5′ sheets and is relatively heavy, messy to cut and has to be installed with special fasteners and the seams with very specific mesh tape. It’s also not 100% waterproof. It is water insoluble. This means that water can get around it and will not break it down but that doesn’t mean it will keep water from getting past it. This means that you either need to prevent water from getting past it entirely or prevent water from getting to the studs if it does. Red Guard is a topical membrane painted on with a brush or roller and when it dries creates one seamless topical membrane. Some people waterproof behind the cement board first using a water vapor barrier, this works too, as long as you waterproof your penetrations when you install the concrete board. I know this is all very stimulating.

Durock is heavy and hard to cut and not easy to install by yourself.

We really did not enjoy building those last bathrooms with the Durock. And even though we were able to diy the shower walls, we still had to hire someone else to waterproof a shower pan for us.

Our shower/bath at our last house.

About two years ago we remodeled our primary bathroom in this house and Mike and I decided to give Kerdi a try. The boards come in 4×8 sheets and weigh just a few pounds each. They cut very easily and quickly with a utility knife, have grids on them for easy referencing and like Durock also have to be installed with special fasteners and tape. However, unlike Durock, once it’s installed it is 100% waterproof and doesn’t require any additional membranes.

The big orange box. That’s what Kerdi systems makes.

Mike and I did our bathroom together. That as the first time we’d done Kerdi and it’s so diy friendly I knew if I had to I could do it on my own. I don’t know if I’d try and do a Durock shower on my own. Plus, Kerdi also makes shower pans and curbs with their system = less subs = less delay.

Mike putting sand around the drain in our primary bathroom shower before we closed it up

The boards go up really fast

Installing the panels is as simple as cutting them to size and screwing them in. Since the boards are 8′ tall and our ceilings are 9′ we added a 1′ section around the top.

Even though the process is really easy and diy friendly, Schluter also has easy to follow videos on YouTube to reference as you go. We installed the fasteners so they slightly dimpled the Kerdi boards. This way when I patch the fasteners the thinset doesn’t cause a bulge where the screw/screw collars are. It took Mike and I a little over an hour to get all the boards up and fasteners in place.

We also installed Kerdi on the ledge and the perimeter of the window. This plywood had to be added on top of the existing floor to support the new shower floor. There used to be a tub here and the hole for the tub drain was much larger.

The Kerdi method does cost a little more, but not much when you take in to consideration all the different steps Durock takes to waterproof it, plus the different trades that have to be involved to build the shower. I also love how lightweight it is and diy friendly. Kerdi does have a competitor called Wedi. I haven’t used their method but once Kerdi’s patent was up they came out so I’d guess they’re very similar.

Then you use Kerdi membrane and unmodified thinset to seal all the seams and as patches where any of the fasteners were used. They also make their own interior and exterior corners for easy corner sealing.

Once the fasteners are in, it’s time to waterproof them and the seams. Pre-cut all of your seams and 4″ square patches before mixing your thinset. Then you’re ready to go and you aren’t letting your thinset dry while you’re cutting your pieces. I used a combination of a 6″ drywall knife and a v-notch trowel to apply the thinset and install the membrane patches/seams.

The fasteners need to be covered with 4″ squares. I cut a bunch of these before mixing the thinnest so I have everything ready to go.

The really cool thing about the membrane is you don’t have to worry about the order that you install the seams, unlike roofing material that has to be installed in a particular order, the Kerdi membrane seals can go in any order, for example I installed the seams, then the corners, but you could do the corners then the seams. I’m going to install the shower pan last, after I tile, that way I don’t get thinset all over my fresh tiled shower pan.

Next week I’ll show you how I tiled the shower and installed the shower pan. Have you ever used the Kerdi method? Let me know if you have or if you’d consider doing it on your own in the comments 🙂

2 Comments

Leave a Reply