I was planning on roughing up the existing pan tiles, installing Kerdi membrane on top and tiling over. It goes against normal reason that a membrane can support tile that peels away from the mortar. Steve, thank you for sharing a plethora of knowledge and pro-tips. Durock also makes foam tile backer board panels, benches, and ramps. It basically has the same application procedures and limitations as the other liquid membranes. You dont want to take any chances. That is the best you can do without a full remodel. 
My parents recently moved in with us (in-law suite) and my father has hired someone to renovate their bathroom. And if the material comes in different thicknesses, I would try to get something thicker if possible (thicker than 12mm), since this will be your only waterproofing layer. I would recommend you first remove any vapor retarder plastic sheet or felt from the stud surface on all the outside shower walls. We did not notice this until two thin layers of red guard had been painted over them. I would also attach your 3/4 ply with screws and again construction adhesive applied to the top of every joist. Almost all the sheet waterproofing brands sell valve and pipe seals (Durock, Mapei, Wedi etc. Bottom line is..if you try to seal the top surface of the tile you will be locking in the moisture that lies between the tile surface and the rubber membrane. The guy doing the work specd cement board. If its a shower that youre building, I would recommend that you waterproof it identical to a regular home shower. Hi Steve, thanks for your quick response! So I would say yes, it is definitely a big deal that they didnt install a membrane. So basically the shower pan will be 3/4 subfloor, Schluter preformed bed pan, then tile. So: do I need to wait a month before I put the shower pan down so I dont have water buildup between concrete and shower pan? That would be my simple recommendation if you would like the easiest and safest protection against moisture problems down the road. I have not used the Proflex waterproofing membrane products so I cant really comment on how they install, or how effective they are. This questionable advice also contributes to thin areas in the membrane as the liquid tends to recede into gaps and crevices. Ive seen dry pack extensions to the standard foam pans but can you extended one such as the hydro ban one. On another note On this outside wall I was just going to butt the durock to the tub flange. I would wonder if this might accumulate condensation and eventually mold. 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How is this code accommodated with a curbless entry? The difference is that this membrane has an exceptionally low .05 perm rating according to the manufacturer. It seems so counterintuative! 36 seems to be most common. In an outside wall that is probably already too thin for an adequate insulation thickness, the moisture moving into the stud cavity behind the niche has an extraordinarily high risk of condensing into water. The wall boards are made from extruded polystyrene foam and have a layer of material on both sides designed for tile mortar bonding. I think your concern is justified. Hi Steve, thanks very much for your detailed explanation. Because the shower floor and shower walls are exposed to lots of moisture and wide temperature changes, this is also a place where grout line cracking can occur. I know theres a lot of competing factors that go in to deciding how to proceed, but I do very much appreciate how well you distill the information to make easier for us understand. I must give you credit for an innovative solution..but. Im about to install a foam shower base after removing an old tub. Steve, well written article with very good information thank you for doing this! ft. When we asked the plumber, he said he would not warrant the work any longer; his pan had been compromised. I lean towards just putting a full (or two) on since you already are covering ~25% of the wall just sealing the screws and corners/seams. I think you hit the right water to mortar ratio when you mentioned the definition of proper adhesion Steve. 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What is best way to waterproof the wall/base joint. it would really depend on how permeable these planks are. You may think that a small amount of water vapor here might be OK because theres a waterproofing membrane protecting the wall from moisture penetration, but it kind of defeats the purpose of using a product like corrugated roofing (unless you are saving a bunch of money).
Wedi has one in the size I need but its $1200!! Hi doing a alcove tub rebuild, to replace a leaking whirlpool tub. This horizontal movement can also cause tile delamination around the crack. Water may never get past the membrane and into the framing, but you would eventually end up with grout line cracking and possible tile delamination. This should be done regardless of the membrane you decide to use, but I always recommend using a really good sheet membrane on any outside wall (like Subliner Dry, Kerdi DS) to reduce moisture permeance as much as possible, especially if its a 24 stud wall. Ceramic tile usually failed faster than porcelain because of higher absorption rates through the tile, but they all eventually failed. Last question. Wedi and Hydro-Blok. A super solid subfloor beneath your Schluter shower pan is actually more important than the rest of your floor because of the immense amount of weight on this part of the floor after the shower is fully installed. You dont necessarily need to get this brand but the technique is sound. Both rooms got tiled walls in the bathing area and on the floor. But unlike the video, I would recommend that you place the rebar supports, especially if the hole is larger than that in the video. The contractor is trying to tell me its not a big deal, and the tile is enough protection for the walls, and suggested a grout sealer. I agree with you that this product is a little expensive. 1. There are some complex physics involved in these systems and frankly most tiling professionals dont really have a clue either. And I can tell you from personal experience that this assumption was not at all acceptable. What a great article! ), but theyre a bit harder to find. These are things I have also considered many times in order to save a bit of money for the client, but still maintain the integrity of the entire assembly. 
As far as I know, Wedi Subliner Dry has the lowest perm rating of all the shower waterproofing membranes in the industry. Because the Durock is slightly thicker than the mounting flange, your wall tile can be extended below the bottom of the board to the tub surface. This video shows exactly how to properly waterproof an entire shower with a mud shower pan, using their Kerdi waterproofing system. It also be a good idea to suspend some wire mesh between the rebar if the hole is bigger than 2 square feet. Going to tilt the wallboard of those lower niche sills with thinset underneath
ProBase is unique among its competitors because it has a fleece covered membrane bonded to its surface. I have tried to remove porcelain tile (set with modified thinset) from Schluter Kerdi and it wasnt easy at all. It does seem quite baffling. A prefab foam bench is the best idea for the shower. I would also suggest screwing and gluing these braces in place using construction adhesive and framing screws. I attempted to watch a video you had linked but its no longer available. After 48 hours I can peel it off like a sticker. Wedi or hydroban membrane on the floor first, then all the walls This code rule is still in place today in most parts of the world but it has always had serious limitations such as inconsistent coverage and varying degrees of moisture permeability. He claims that thats what red guard is for, to waterproof the screws, and that the curb is good. The reality is that at least one of the walls of your shower will likely be on an outside wall. I dont really have a favorite brand but I have used several of the Mapei mortars and Schluter All-Set. Hydro Block seems perfect. I think it would be very risky to keep it especially now that you have demoed the upper half of the shower. Or no? That means that your waterproofing may be all good. Then you can do it right by installing a mortar or foam shower base (with an integrated membrane bonding shower drain) and an under-tile sheet membrane over the shower walls and base. The last 1/3 of the video shows the corner tape attachment. As I already mentioned, Kerdi Board is the most popular of the foam wall boards out there. Steve Gehrmann is a remodeling contractor (SKG Renovations) as well as a partner in Redblock Industries. You must allow 12 hours to cure before flood testing. I am building a campervan shower/mud room. We are using 26 studs because we were told that the wall had to be 6 wide to install nitches. I received different pieces of advice: (1) Replace the shower mixer, then apply clear waterproofing membrane over the tiles; and (2) remove and retile the entire shower, like what you suggested above. 