Bravo man, you did a great instructional video. I have built over 14 showers in 2019, mostly self taught, however last year I got certified as a bathroom remodeler, and did Schluters training for their products. That’s about the extent of my schooling in this industry. I have never had a shower call back........yet. Fingers crossed. I normally do a shower pan(Sterling, proflow, or Kohler) white shower pans and then tile the walls, usually prefer to use schluter kerdi foam board(easy on my body/back, super fast, less head ache doing all the cuts with a utility knife right in the shower. I love kerdi board. I have done one shower with a tile floor, and I used the schluter shower kit. Which has the foam pan already made, waterproof liner built on, everything you need. It’s quick and fairly easy. But it’s expensive as hell. It has its uses and place depending on the job. I am currently building a tile shower and tile floor, made my own pitch mud bed and planning to use aquadefense from mapei (same thing as red guard). Didn’t know how to do the drain, or why it needed the second mud bed after the red guard. Now I know, and I know my build will be trouble free from call backs. Knowledge in shower building is the most valuable thing. Besides experience, but that money can’t buy. Thanks for your time doing this video.
I too love the foam board. Worked with a tiler helping him. But on my own shower had to go with Durock because I couldn't afford the other. That board is so heavy working by your self, especially as a female and even harder to cut. I'll get there!
Dude!! I've ben searching for this information for 2 weeks! I'd have been done by now with the shower project if I found this earlier! I've only watched a bazillion videos some good some awful but no one discussed the most important aspect; the engineering of the project. I even lost sleep, waking in the middle of the night to go watch more useless videos (and a couple very good ones as well). I knew I had one chance to get it right. Thank you, thank you, thank you!
And I'm the only one that thought I lost sleep over this crap? LOL They also say NEVER put your backer board in the cement pan? I accidentally did and was freakin out! I see he goes all the way with his backer. I feel a lot better!
Bro you dont need no speed finish or mesh tape with red guard. The whole purpose of red guard is to fill every nook and cranny. You could red guard cardboard and it will be waterproof. 🤦🏿♂️
I'm not commenting on this to be mean or a jerk. I just want you to know that this type of shower pan build is not correct. You are using a weeping flange drain and all the principles and standards for the install of it have been over looked. That flange is designed to have a pre sloped base, a vinyl liner, and a sloped mud bed. Gravity and capillary action will force water to work its way toward the flange and down the weep holes. Mixing a liquid membrane with this type of flange is a sure recipe for a failure. Fortunately this is being done on a concrete slab, if it were on a second floor in a framed home you would see water damage very quickly. DYI'rs need to understand the principles of design that go into a shower pan. There are two systems for shower pans. Either a weeping flange like that one, with all the proper components that go along with it or, a bonded flange system, like a Schluter drain which is designed to have a membrane bonded to it, whether you use a mortar bed or foam. Don't mix both systems. Unfortunately, I tear out a bunch of shower failures that have been constructed like this. Water will work its way into the mortar bed and with all that liquid membrane on top it will sit and stagnate there. If it's on a second floor, it will work its way onto the wood subfloor and ceiling below.
I almost paid $5K for someone to do this because I had so many questions. Your video is exactly what I needed! I’ve been searching weeks for instruction on building a custom shower pan with a linear drain on a slab - and using red guard. I am very excited and feel more prepared now. Thank you!!!!!
You can put the backer board in the concrete? There's a lot of contradictions about how to build a shower. Will it wick moisture if it's set in the mud pack?
Bad tecnik first waterproof the concret slab mesh tape in corner 3 coats curb have to be built with bricks then thinset to make sure the drypack gone stick on red gard make the slope then let cure the dry pack 3 days then mesh tape again redgard few coats never crack or leak
I just want to say what a great job you did on this video. I'm about to do the same job on a 8x5 shower. i''m a 20 year exp remodeler and your doing it right. Your commentary was excellent as well as the steps you followed. Not easy to do. Thank you! Dave
I have some modest concerns over this particular linear drain, similar to one I've installed. My issue is where the drain meets the mudpack on the shower pan. I've built up the floor to meet the linear drain as you did, leaving some room for tile. I intend to waterproof the floor with redguard again, my pre slope I used a pvc liner. My guess is that the red guard will adhear to the edge of the linear drain. I need this because there is a potential of leakage between stainless steal linear drain and shower pan. Of course the weap holes are second protection, but would rather water not even think about penetrating between preslope and shower pan. What I don't like is that the linear drain will be about 1/4 inch above my final red guard coat. And my final redguard coat can't go to the top edge of the linear drain, must be about 1/8 inch below that. That means on the edge of the linear drain, 1/8 inch down, it will have redguard that can't be compromised, but it is a vulnerable area. I intend to do a good job with mortar waterproofing to have a triple layer of protection. Beyond that, nothing is perfect. Nice little video. Thx.
I have wondered the same thing. What did you do in the end? I thought maybe to apply a thin layer of caulk around the linear drain itself once everything else is set.
@@JonathanPuddle I followed my plan that I wrote, " That means on the edge of the linear drain, 1/8 inch down, it will have redguard that can't be compromised, but it is a vulnerable area. I intend to do a good job with mortar waterproofing to have a triple layer of protection." The thing is I never worked with Red Guard before this project. It's basically like a caulking, but more pliable with a brush. I recall that I taped the top edge, about 1/8th inch below the very top edge (so it would not show above the tiling) and after using the redguard I felt pretty confident about the whole job, although if there is a point of failure it may be at this point. In my shower the liner drain is forward and no one really steps on it. I think if it was center it would still be fine, but I've also got that going for me... I really don't think Caulking will add value an possibly it will interfere with a tight fitting between the tiling and the edge of the drain. I think you'll be just fine with redguard.
@@JonathanPuddle I was taking a shower earlier and then I remembered I also use premium grout in the tile that grout has some sort of water sealer inside of it... layers of protection
Hi, When you do preslope Is it all in one direction towards the linear drain? Do we need to do borders and then slope? My shower layout is exactly like yours and on concrete slab. I am abit afraid about the height of the flange and drain but will figure out! Thanks for the video
I would do preslope to a point , the pipe, as that’s the only location with the weep holes. Then the mud bed can be flat sloped to the drain area to support large tiles
That system takes forever....First day: Backerboard, drain, preslope. Second day: Waterproofing and flood test ( You're actually supposed to wait 3 days for the deck mud to dry prior to redgarding it, you skipped this requirement.) Third day: Final slope, go home. 3 days just to prep it, maybe longer if your redgard doesn't dry fast enough...Why not use a divot method to gain a day?
Hello Will, Thanks for the comment. The system does take time. The goal of my video was to educate homeowners on how to save a significant amount of money by doing it yourself. I firmly believe Redgard or equivalent product produces a quality job result. If someone needs a faster job completion, just hire a professional and pay the cost. Best Regards
I plan on doing something very similar in my shower with a linear drain. Have you considered setting the drain lower by 1.5 inches initially, and then leaving a divot for it during your preslope? Then you could let the mortar dry, redgard everything (divot included) then install your drain and mortar it in place. After that, you wouldn't have to apply the second layer of mortar. You could tile directly onto the redgard surface, and you would have far less mortar absorbing water during use. Plus your threshold could be lower too. Just my thoughts.
You are the first person I can find actually using this method (redgard without a pan liner with a clamping drain)! I'm in a situation where I'm doing an above slab/above subfloor plywood framed roman tiled tub (tricky I know) and folding a pan liner into the complex shapes (let alone finding one that's large enough) presents a serious challenge. I'm considering your exact method to solve these complications. AKA covering the tub walls with cement board, then putting down roofing felt on my plywood tub floor and packing my sloped mud bed to be level with the drain flange, then covering it all with redgard -- reinforcing all seams covering all fasteners and the drain flange with red gard & mesh tape and tightening down the clamp ring onto the redgard+mesh tape. I believe your method is sufficient for a shower install but would you trust it in a tiled roman tub situation like mine where it's not just an occasion 2 inches of water for a few minutes when the drain might back up vs. a tub where it's a 15 inch column of water for 1-2 hours a day every day? My previous plan was a preslope mud bed then hot mop or PVC pan liner (May consider a 10'x10' EDPM pond liner as they are larger), then scratch coat vertical tub walls & stick on lathe folding over the tub lips/arm rests held in place with deck mud on the lip/arm rests and lathe fasteners 6" up the wall above the tub lip where the pan liner ends, then just float the tub walls with lathe reinforced wall mud to avoid putting any fastener penetrations through the tub membrane or hot mop felt.. I've seen a few roman tub builds done with cement backer board & mesh reinforced hydraban liquid membrane on the tub walls and mud bed using your method (liquid membrane as the only panliner with a clamp drain) here on youtube but no one ever followed up with long term success rates, and one guy had a drain leak right away and didn't explain why? Your method would save me a serious amount of money, time and headache, and I'm starting to wonder if it's worth all of the extra expense and headache to go with a pan liner(or hotmop) and lathe & float all the tub walls? Would love your opinion! thanks! -Gary.
Nice video Rob but All wood curbs fail. to build a wooden curb is a promised failure. let me say this again. All wood curbs Fail. Curbs need to be made of solid cement. All wood shrinks. Wood touching concrete expands. Let me say this again. All wood shrinks. When, not if that curb shrinks but when that curb shrinks you will acquire gaps between the layers thus 2x4's that can "bounce" up and down the thickness of a dime. I see you shimmed plywood and have air gaps. That curb is an epic failure waiting to happen. Solid curbs I say, solid. You don't find wood curbs under the tile work in Rome because they knew better. So to be clear, All wood curbs Fail, wood shrinks and expands while tiles and grout do not. A wooden curb will fail, its inevitable. Don't get me going on Redgard either. I'll spare you.
No!!! as a professional, with hundreds of showers constructed, I warn you not to replicate this, especially over a wood subfloor. All the drainage principles of a shower pan design have been violated here.
@@marcopoulin1897 Whats wrong with putting thinset on the redguard? Isn't that allowed when u do it on the wall? Also, when ppl use the OAtey liner they don't see to have any problems with the second mud layer
From my research and experience doing just this myself you use the Red Guard to adhere the fiber tape to the shower. I personally was very pleased with this method. Feel free to look at my shower video as well showing these two materials.
Great ONE video you have. You couldnt have done that with a standard pan liner? I also remove the heigh adjusting wheels off the drain. Good job. Just not too sure about the redgard as a liner. I use it on my denshield walls in on the seams and corners.
Liner is a thing of the past. The red guard is basically taking its place in the field. I give 10 year guarantee on bathrooms and I do it almost exactly like this too
I'm using a standard Kerdi drain, do I have to do 2 layers of deck mud like you did here with Redgard in between? I was planning to just build the 1st layer up to the right height to begin with then Redgard the top surface.
Hello Randy, First, I am not a professional plumber. However, I have used my Redgard system on 6 showers over the last 10 years. There has been no issues with the install. I have a few comments. 1. First I would not put shower floor tiles directly on Redgard. The shower tiles/tile mortar could puncture the Redgard over time. The second layer of deckmud acts as a buffer to disperse the force from your feet. I have tiled directly over Redgard in a dry environment using the Redgard as a crackstop. 2. A critical step in the Redgard installation is sealing the drain flange. My installation sandwiches the Redgard/Cloth with the 2 piece drain flange. This means the top of the drain flange and shower drain are above the Redgard surface. So the second layer of deckmud fills the void from the Redgard to the drain top. 3. The second layer of deckmud adds to the rigidity of the structure. There can be no movement in the shower subsurface. This is especially true over a wooden floor. I hope that helps. Robert
Randy, no you dont have to. Your Kerdi linear drain already has the membrane attached to it. So just set your slope to the correct height, install your drain and then your kerdi membrane over top of that. Lots of videos on youtube that explain how to use the Kerdi linear drain. Its easier than this kind of drain that has no lip to attach a membrane overhang to.
This is one of the most helpful videos on this subject I've found (linear drain install with liquid waterproofing membrane). Bravo. Thank you so much!
Yep was really hard to find lol, really appreciate the video!
Bravo man, you did a great instructional video. I have built over 14 showers in 2019, mostly self taught, however last year I got certified as a bathroom remodeler, and did Schluters training for their products. That’s about the extent of my schooling in this industry. I have never had a shower call back........yet. Fingers crossed. I normally do a shower pan(Sterling, proflow, or Kohler) white shower pans and then tile the walls, usually prefer to use schluter kerdi foam board(easy on my body/back, super fast, less head ache doing all the cuts with a utility knife right in the shower. I love kerdi board. I have done one shower with a tile floor, and I used the schluter shower kit. Which has the foam pan already made, waterproof liner built on, everything you need. It’s quick and fairly easy. But it’s expensive as hell. It has its uses and place depending on the job.
I am currently building a tile shower and tile floor, made my own pitch mud bed and planning to use aquadefense from mapei (same thing as red guard). Didn’t know how to do the drain, or why it needed the second mud bed after the red guard. Now I know, and I know my build will be trouble free from call backs. Knowledge in shower building is the most valuable thing. Besides experience, but that money can’t buy. Thanks for your time doing this video.
Is the 2nd mud bed above red guard (or kerdi membrane) still needed on slab foundation?
I too love the foam board. Worked with a tiler helping him. But on my own shower had to go with Durock because I couldn't afford the other. That board is so heavy working by your self, especially as a female and even harder to cut. I'll get there!
Pretty accurate, that's a crazy slope in your drawing.......... I know it's just an example
Dude!! I've ben searching for this information for 2 weeks! I'd have been done by now with the shower project if I found this earlier! I've only watched a bazillion videos some good some awful but no one discussed the most important aspect; the engineering of the project. I even lost sleep, waking in the middle of the night to go watch more useless videos (and a couple very good ones as well). I knew I had one chance to get it right. Thank you, thank you, thank you!
Me2
And I'm the only one that thought I lost sleep over this crap? LOL They also say NEVER put your backer board in the cement pan? I accidentally did and was freakin out! I see he goes all the way with his backer. I feel a lot better!
Bro you dont need no speed finish or mesh tape with red guard. The whole purpose of red guard is to fill every nook and cranny. You could red guard cardboard and it will be waterproof. 🤦🏿♂️
Expansion and contraction. Slight preventative measure against separating and cracking. Aiding in the few years of life this shower will have.
I'm not commenting on this to be mean or a jerk. I just want you to know that this type of shower pan build is not correct. You are using a weeping flange drain and all the principles and standards for the install of it have been over looked. That flange is designed to have a pre sloped base, a vinyl liner, and a sloped mud bed. Gravity and capillary action will force water to work its way toward the flange and down the weep holes. Mixing a liquid membrane with this type of flange is a sure recipe for a failure. Fortunately this is being done on a concrete slab, if it were on a second floor in a framed home you would see water damage very quickly. DYI'rs need to understand the principles of design that go into a shower pan. There are two systems for shower pans. Either a weeping flange like that one, with all the proper components that go along with it or, a bonded flange system, like a Schluter drain which is designed to have a membrane bonded to it, whether you use a mortar bed or foam. Don't mix both systems. Unfortunately, I tear out a bunch of shower failures that have been constructed like this. Water will work its way into the mortar bed and with all that liquid membrane on top it will sit and stagnate there. If it's on a second floor, it will work its way onto the wood subfloor and ceiling below.
Appreciate this! No nonsense, showing your work 👊👊
Why not just by a bag of deck mud mix ????
Not available in all regions. Can't find it where I am in the Portland, OR area. I just use Sand/Topping mix.
there is a lot of garbage on u tube on this subject. this is no exception
No shower liner?
No need. That's what the redguard does.
I almost paid $5K for someone to do this because I had so many questions. Your video is exactly what I needed! I’ve been searching weeks for instruction on building a custom shower pan with a linear drain on a slab - and using red guard. I am very excited and feel more prepared now. Thank you!!!!!
You can put the backer board in the concrete? There's a lot of contradictions about how to build a shower. Will it wick moisture if it's set in the mud pack?
Based on my research, it appears the redguard will keep it from getting wet.
Bad tecnik first waterproof the concret slab mesh tape in corner 3 coats curb have to be built with bricks then thinset to make sure the drypack gone stick on red gard make the slope then let cure the dry pack 3 days then mesh tape again redgard few coats never crack or leak
I just want to say what a great job you did on this video. I'm about to do the same job on a 8x5 shower. i''m a 20 year exp remodeler and your doing it right. Your commentary was excellent as well as the steps you followed. Not easy to do. Thank you!
Dave
To much work use shluter pan
I have some modest concerns over this particular linear drain, similar to one I've installed. My issue is where the drain meets the mudpack on the shower pan. I've built up the floor to meet the linear drain as you did, leaving some room for tile. I intend to waterproof the floor with redguard again, my pre slope I used a pvc liner. My guess is that the red guard will adhear to the edge of the linear drain. I need this because there is a potential of leakage between stainless steal linear drain and shower pan. Of course the weap holes are second protection, but would rather water not even think about penetrating between preslope and shower pan. What I don't like is that the linear drain will be about 1/4 inch above my final red guard coat. And my final redguard coat can't go to the top edge of the linear drain, must be about 1/8 inch below that. That means on the edge of the linear drain, 1/8 inch down, it will have redguard that can't be compromised, but it is a vulnerable area. I intend to do a good job with mortar waterproofing to have a triple layer of protection. Beyond that, nothing is perfect. Nice little video. Thx.
I have wondered the same thing. What did you do in the end? I thought maybe to apply a thin layer of caulk around the linear drain itself once everything else is set.
@@JonathanPuddle I followed my plan that I wrote, " That means on the edge of the linear drain, 1/8 inch down, it will have redguard that can't be compromised, but it is a vulnerable area. I intend to do a good job with mortar waterproofing to have a triple layer of protection."
The thing is I never worked with Red Guard before this project. It's basically like a caulking, but more pliable with a brush. I recall that I taped the top edge, about 1/8th inch below the very top edge (so it would not show above the tiling) and after using the redguard I felt pretty confident about the whole job, although if there is a point of failure it may be at this point. In my shower the liner drain is forward and no one really steps on it. I think if it was center it would still be fine, but I've also got that going for me... I really don't think Caulking will add value an possibly it will interfere with a tight fitting between the tiling and the edge of the drain. I think you'll be just fine with redguard.
@@JamesEid Thanks!
@@JonathanPuddle I was taking a shower earlier and then I remembered I also use premium grout in the tile that grout has some sort of water sealer inside of it... layers of protection
Hi,
When you do preslope
Is it all in one direction towards the linear drain?
Do we need to do borders and then slope? My shower layout is exactly like yours and on concrete slab.
I am abit afraid about the height of the flange and drain but will figure out! Thanks for the video
I would do preslope to a point , the pipe, as that’s the only location with the weep holes. Then the mud bed can be flat sloped to the drain area to support large tiles
And for the second mix you used mortero like in the first? I am asking just to make sure because I am building my own shower
That system takes forever....First day: Backerboard, drain, preslope. Second day: Waterproofing and flood test ( You're actually supposed to wait 3 days for the deck mud to dry prior to redgarding it, you skipped this requirement.) Third day: Final slope, go home. 3 days just to prep it, maybe longer if your redgard doesn't dry fast enough...Why not use a divot method to gain a day?
Hello Will,
Thanks for the comment.
The system does take time. The goal of my video was to educate homeowners on how to save a significant amount of money by doing it yourself. I firmly believe Redgard or equivalent product produces a quality job result. If someone needs a faster job completion, just hire a professional and pay the cost.
Best Regards
I found after installing the upper shower flange mount that a little bit of water will sit at the level of the lower flange.
I plan on doing something very similar in my shower with a linear drain. Have you considered setting the drain lower by 1.5 inches initially, and then leaving a divot for it during your preslope? Then you could let the mortar dry, redgard everything (divot included) then install your drain and mortar it in place. After that, you wouldn't have to apply the second layer of mortar. You could tile directly onto the redgard surface, and you would have far less mortar absorbing water during use. Plus your threshold could be lower too. Just my thoughts.
You are the first person I can find actually using this method (redgard without a pan liner with a clamping drain)! I'm in a situation where I'm doing an above slab/above subfloor plywood framed roman tiled tub (tricky I know) and folding a pan liner into the complex shapes (let alone finding one that's large enough) presents a serious challenge. I'm considering your exact method to solve these complications. AKA covering the tub walls with cement board, then putting down roofing felt on my plywood tub floor and packing my sloped mud bed to be level with the drain flange, then covering it all with redgard -- reinforcing all seams covering all fasteners and the drain flange with red gard & mesh tape and tightening down the clamp ring onto the redgard+mesh tape. I believe your method is sufficient for a shower install but would you trust it in a tiled roman tub situation like mine where it's not just an occasion 2 inches of water for a few minutes when the drain might back up vs. a tub where it's a 15 inch column of water for 1-2 hours a day every day? My previous plan was a preslope mud bed then hot mop or PVC pan liner (May consider a 10'x10' EDPM pond liner as they are larger), then scratch coat vertical tub walls & stick on lathe folding over the tub lips/arm rests held in place with deck mud on the lip/arm rests and lathe fasteners 6" up the wall above the tub lip where the pan liner ends, then just float the tub walls with lathe reinforced wall mud to avoid putting any fastener penetrations through the tub membrane or hot mop felt.. I've seen a few roman tub builds done with cement backer board & mesh reinforced hydraban liquid membrane on the tub walls and mud bed using your method (liquid membrane as the only panliner with a clamp drain) here on youtube but no one ever followed up with long term success rates, and one guy had a drain leak right away and didn't explain why? Your method would save me a serious amount of money, time and headache, and I'm starting to wonder if it's worth all of the extra expense and headache to go with a pan liner(or hotmop) and lathe & float all the tub walls? Would love your opinion! thanks! -Gary.
Hey how did that go? I'm working on something similar.
I did a roman tub all tile I used hydroban and 1" plywood with 1/2 cement board
Did you apply Redgard to the final surface of the mud before tiling it??? (I saw you put Redgard on your preslope).
If he didn't, he forked up.
Does no good if you dont show all your work
Nice video Rob but All wood curbs fail. to build a wooden curb is a promised failure. let me say this again. All wood curbs Fail. Curbs need to be made of solid cement. All wood shrinks. Wood touching concrete expands. Let me say this again. All wood shrinks. When, not if that curb shrinks but when that curb shrinks you will acquire gaps between the layers thus 2x4's that can "bounce" up and down the thickness of a dime. I see you shimmed plywood and have air gaps. That curb is an epic failure waiting to happen. Solid curbs I say, solid. You don't find wood curbs under the tile work in Rome because they knew better. So to be clear, All wood curbs Fail, wood shrinks and expands while tiles and grout do not. A wooden curb will fail, its inevitable. Don't get me going on Redgard either. I'll spare you.
Lolol.
Make the curb with bricks never fail
Can this method be done over plywood subfloor?
No!!! as a professional, with hundreds of showers constructed, I warn you not to replicate this, especially over a wood subfloor. All the drainage principles of a shower pan design have been violated here.
To remove accidental drain droppings use a shop vacuum
So for the preslope you used mortar?
Ok i re-watch the video and I got it 👍 😅
I appreciate the hard work you put into explaining this video. Very informative. Keep up the good work
I like your style, pretty detail but somethings ill do different but still really. I like to learn from every body. 👌
Why the preslope when using Redguard? I think it is unnecessary.
Preslopes are a thing of the past with these liquid membranes in the market...
Right plus you have to put thinset then the drypack on top because drypack doesnt stick on concret or redgard
@@marcopoulin1897 Whats wrong with putting thinset on the redguard? Isn't that allowed when u do it on the wall? Also, when ppl use the OAtey liner they don't see to have any problems with the second mud layer
Do you use fiberglass resin with the fiberglass tape patch or just more red guard?
From my research and experience doing just this myself you use the Red Guard to adhere the fiber tape to the shower. I personally was very pleased with this method. Feel free to look at my shower video as well showing these two materials.
24:15, do you leave those boards in when you screed?
No, the wood is removed. The wood impressions are then filled with additional deck mud.
oh i see.
also, is it safe to sink the cement board into the pan? i’ve heard others recommend not to do that.
thank you very much for your help!
Great ONE video you have. You couldnt have done that with a standard pan liner?
I also remove the heigh adjusting wheels off the drain. Good job. Just not too sure about the redgard as a liner. I use it on my denshield walls in on the seams and corners.
Liner is a thing of the past. The red guard is basically taking its place in the field. I give 10 year guarantee on bathrooms and I do it almost exactly like this too
@@555-s4e i disagree. KERDI membrane and Laticreete fabric is taking over more so.
@@XCBen that's a waste of time red guard is faster and equally as good
@@555-s4e I agree, but regard isn't replacing liner in the field. Which is what you wrote. Kerdi and Laticrete is.
A 24 hour water test should ease anyone’s nerves no matter what is used as a liner.
I'm using a standard Kerdi drain, do I have to do 2 layers of deck mud like you did here with Redgard in between?
I was planning to just build the 1st layer up to the right height to begin with then Redgard the top surface.
Hello Randy,
First, I am not a professional plumber. However, I have used my Redgard system on 6 showers over the last 10 years. There has been no issues with the install.
I have a few comments.
1. First I would not put shower floor tiles directly on Redgard. The shower tiles/tile mortar could puncture the Redgard over time. The second layer of deckmud acts as a buffer to disperse the force from your feet. I have tiled directly over Redgard in a dry environment using the Redgard as a crackstop.
2. A critical step in the Redgard installation is sealing the drain flange. My installation sandwiches the Redgard/Cloth with the 2 piece drain flange. This means the top of the drain flange and shower drain are above the Redgard surface. So the second layer of deckmud fills the void from the Redgard to the drain top.
3. The second layer of deckmud adds to the rigidity of the structure. There can be no movement in the shower subsurface. This is especially true over a wooden floor.
I hope that helps.
Robert
Randy, no you dont have to. Your Kerdi linear drain already has the membrane attached to it. So just set your slope to the correct height, install your drain and then your kerdi membrane over top of that. Lots of videos on youtube that explain how to use the Kerdi linear drain. Its easier than this kind of drain that has no lip to attach a membrane overhang to.
Wrong
Why?