Elastomeric or liquid waterproofing membranes are one of the most convenient methods of waterproofing shower walls before installing tile. These membranes consist of products such as Custom Building Products’ Redgard and Laticrete’s Hydrobarrier and Hydroban and Mapei’s Aquadefense. I will refer to all the membranes as Redgard for the purposes of this post, but they all work nearly the same way.
These materials can be installed with a regular paint brush, paint roller, trowel, or even sprayed on. They are applied to your shower walls then tile is installed directly onto it. When I use these products I always use a cement-based backerboard as the wall substrate without a plastic vapor barrier.
It is imperative that you do not install plastic behind your walls since this would create two waterproof membranes with your substrate between them. Having two barriers this close together leaves open the chance of trapping moisture between them with no way for it to evaporate. This may lead to mold.You must also tape the backerboard seams with fiberglass mesh drywall tape.
The easiest way I have found to install Redgard is, after the walls are prepped properly, start with a paint brush and thoroughly coat all the corners and angles. The membranes are more the consistancy of pudding than paint so don’t be afraid to scoop it out to spread it. You should be used to it after a few minutes.
After all the corners are coated I use a paint roller and pan to cover the walls. Redgard is bright pink – I mean pepto-bismol pink, it almost glows in the dark. This is useful in that when it is dry it turns dark red. The other membranes are similar. Laticrete’s Hydroban, for instance, goes on light green and dries forest green.
Just thoroughly coat the entire inside of your shower until the whole thing is bright pink – enough so it can be seen from space. That’s it – go have an adult beverage until it dries. You must then do a whole second coat the same way. Make sure the first coat has fully changed color before applying the second coat. If you are using a roller Custom (the company that makes redgard) recommends that you roll on the first coat horizontally and the second coat vertically to ensure full coverage. (Thanks for that Davis)
Most of the product specifications for these materials state two coats to be sufficient, and it probably is. I normally use three coats. I’m weird like that. Unless you have a steam shower or something similar, two coats would probably be enough. It’s up to you.
These products shrink a bit as they dry so you must make sure that it has not shrunk enough to create holes or voids in places such as corners and seams. You need a full coating for the product to be effective. When you are finished you should let the walls completely dry for a day before tiling.
Your tile can then be installed directly onto your walls over the membrane with a proper thinset mortar. When these products set they will create a rubber-like coating on your walls that is waterproof. When used on shower walls it is a (relatively) quick, effective water barrier for your installation.
These products can also be used as waterproofing on your shower pans in leiu of a regular pan membrane. Make sure your specific product includes specifications for this application if you choose to do that. Check the respective website for your particular product. I do know you can do this with Redgard, Aquadefense, and Hydroban.
I also use these products for main or additional waterproofing on things like shower niches and concrete wall in basements, places where it is difficult to have a plastic vapor membrane behind the backerboards. Basically any place that does not have waterproofing between the tile and shower framing. I always have Redgard with me. The versatility of these products make them a integral part of my shower waterproofing toolbox.
The only drawback for these products, if you choose to look at it that way, would be the price. They are a bit expensive. You may be able to get better prices by ordering online but make sure you take shipping costs into consideration. You can get a gallon of Redgard online for about $45.00 plus shipping. That should be enough to do a regular tub surround. That is a five foot back wall with two 3 foot side walls. For larger showers you can also get a 3.5 gallon bucket.
Make sure to check the website for your product, they have a load of information for them. As always, if you have any questions feel free to leave a comment for me.
Need More Information?
I now have manuals describing the complete process for you from bare wall studs all the way up to a completely waterproof shower substrate for your tile. If you are tiling your floor and walls and using a liquid membrane you can find that one here: Liquid Topical Waterproofing Membranes for Floors and Walls.
If you are just tiling around your tub or pre-formed shower base you can find that manual here: Liquid Topical Waterproofing Membranes for Shower Walls.
No question. Just a statement. Roger “The Floor Elf,” you are THE Man! Thanks for this site.
Thanks Dan! But, you know, to be honest – YOUR the man.
Hell, your name even rhymes with it.
I’m just building a 5’x5′ steam shower in my basement. If I’m using can I use cement board directly on the wood studs of the walls and ceiling and then use the RedGuard over top of the cement board? Will this be a sufficient moisture barrier to prevent the steam from penetrating the walls?
Above the glass door, I’m installing a transom to allow excess steam to escape and be taken away by the bathroom fan which is situated directly outside the transom.
Thanks, in advance, for the time.
Hi Barry,
Nope, steam showers are a whole different animal.
Redgard is fine for your waterproofing but you also need a vapor barrier over your studs – yes, both. The vapor permeability rating (the amount of water vapor that can penetrate a membrane) of redgard is suitable for steam showers but all liquid membranes require an additional moisture barrier against your studs. And tar paper (roofing paper) is actually a better barrier against your studs than plastic sheeting would be in this application. You also need insulation in all your wall cavities surrounding the shower. The transom with the fan directly outside is ideal.
Laticrete has made available a manual describing correct construction procedures for steam showers and rooms and includes everything in it you need to know. It is long but when building a steam shower there are a great deal of things that need to be taken into consideration. You can download the pdf here: (It is a pdf file – so if your computer starts moving like a herd of turtles when you click the link – that’s why)
DS-125 Tiled Steam Room and Steam Shower Technical Design Manual
Hope that helps. If you have any questions that manual doesn’t answer (and I doubt that) please don’t hesitate to ask.
Hi Roger, Really like you website and have found it most imformative. I need your input on a couple of questions. Here is what I am doing/did: ripped out piece of crap fiberglass unit shower that was installed incorrectly and replacing it with a 36″x36″ tile shower. Shower is in corner of a bathroom in the basement so it located on a slab. Using Readi Tile preformed shower pan with their flashing (flashes pan/backer). Using hardibacker board for walls and redgard on interior shower side walls. Unusual situation in that the bathroom is dugout and has earth walls about 4′ tall located approximately 1 foot away around two of the four shower walls. In order to separate the stud walls (walls are on slab not earth) from the earth walls, I utilized faced fiberglass (paper vapor facing towards interior, unfaced towards earth wall) and then utilized Tyvek homewrap on outside of wall against the unfaced fiberglass. My understanding with Tyvek is that it allows water vapor to pass thru, but not water. Since the basement bathroom is located in the center of the basement, I don’t think water from outside will be an issue, but I utilized Tyvek to essentially protect the walls/insulation and clean it up a bit (I figured it would be better than just leaving the fiberglass exposed). Here are my questions: 1) after reading several other posts, I assume I need to to make several holes in the facing of the fiberglass insulation that faces inwards towards the exterior shower wall. Do I need to do the same with the Tyvek? 2) I assume I don’t redqard the pan, just the walls ,correct? 3) Since the wall and pan will be flashed, I assume I stop the redgard before the wall/pan seem, correct?
Hey Jeff,
1) Yes, you need to make holes or slits in the facing of the insulation. You do not need to do that with the tyvek – it allows vapor transmission.
2) Correct – you do not redgard the pan, it is already waterproof, just the walls.
3) Yes, stop the redgard before the wall/pan seam but make sure the redgard goes down over the top of the flashing so that water can run down the redgard on the wall and when it gets to the bottom of the redgard it is already below the top of the flashing – KnowWhatIMean? And just so you know – getting redgard on either the pan or the flashing isn’t going to hurt anything – so don’t be shy about it.
Thanks for your reply. Just curious, is the hardiboard treated with redgard better than denshield. In reading your “preparing a shower wall for tile” I assume you start with best system and go to the worse system. I don’t have any experience with denshield, but it seams lighter and already has built in waterproofing. This seems easier than redgard. I guess what I am asking is if it were your shower which method would you go with?
Hey Jeff,
In my opinion yes, the redgard over hardi is a better method but they both effectively work the same. They both end up with the waterproofing directly behind the tile – topical waterproofing. The hardi method is a more solid, durable installation over the long haul but they both work the same and are suitable installations. And yes, the denshield is lighter – a lot lighter. And a lot quicker. You do need to make sure you follow the installation procedures with regards to silicone in the seams between the sheets and using the proper screws, etc.
Either one will work just as effectively as the other. If it were my shower and I did not use kerdi (which I would) the method would depend on how much time I was willing to spend for the waterproofing. Denshield can be fully installed and waterproofed in about two hours, redgard and hardi would take upwards of a day-and-a-half or more depending on how many layers you install.
What is the warranty for RedGard?
In the product description brochure from Custom Building Products, the warranty is 1 year.
However, elsewhere on the Website, a lifetime warranty for residential application is mentioned, but seems to require using all of their products for an installatiion. “A complete CBP system of products, including surface preparation, mortars and grout materials, must be used to qualify for this limited warranty.”
I also just found that Schluter Kerdi only provides a 5 year warranty. Even 5 years is ridiculously inadequate for the application.
Now I am wondering if my risk is lowest if I use the inexpensive, older, common method, i.e., plastic on studs down to inside of shower pan liner, sloped shower pan liner (into weep holes of 3 piece tile drain) between 2 layers of concrete, all on top of felt/tar paper on floor.
Thanks.
Hey Allen,
I don’t know. I don’t concern myself with specific manufacturer’s warranty periods. My warranty to my customers lasts beyond any warranty they will receive from them anyway. Most manufacturers will offer a lifetime warranty if their product is used exclusively and CORRECTLY throughout the entire installation. Call custom building products and ask them – they’ll be more than happy to give you the full details.
A large reason for the five year warranty from Schluter is because the product was made available to DIY’ers such as yourself.
Here is the part with which you should be concerned: Your risk is lowest not with a particular product, but with the proper application of whichever method you choose. That’s it. Any of the three methods you’ve mentioned in all of your questions: Traditional, Kerdi, or Redgard, will all last for as long as you wish the shower to remain – IF they are installed properly.
Each method has it’s own advantages and disadvantages – that is what you should use to decide which method you choose to utilize. Basing it on which product gives the longest warranty is not an accurate gauge for that decision. A traditional shower construction method gives you no warranty – but I’ve ripped out (literally) 60 year-old showers which utilize this method.
Decide if you want a traditional method, topical method, or a combination of both (traditional floor, topical on walls) and then decide which product or products to utilize. The manufacturer’s warranty (for these products, anyway) should not be a concern in that decision – I give a lifetime warranty on the product with a five year warranty. They all work when installed correctly.
For a shower pan, would a Prospec slope layer (Proform PF-102), followed by 1 or 2 1/2″ hardiebacker layers, topped by Redgard work with the Oatey 3-piece tile drain? (Screwed in, there is a 1/4″ gap between the toop of the clamping ring and the top of the grate.) Do I need thin-set mortar under any of these layers?
In any case, to make RedGard the final seamless waterproofing layer on shower walls and floor, I assume the Hardiebacker layer must stop somewhere short of the clamping ring so the ring can clamp over the RedGard, which directs moisture to the pea gravel shielded weep holes. Do I fill the remaining gap between the Redgard and the grate barrel with thin-set mortar? Where exactly should the Hardiebacker layer stop relative to the Oatey drain base and/or clamping ring?
Thanks.
Hey Allen,
I’m not exactly sure that I’m understanding what you are asking. Are you asking if you can use hardi as the substrate for your shower floor in lieu of deck mud? If so then no, absolutely not. And if you are using redgard as your waterproofing with a normal 3-piece clamping drain you need to utilize the ‘divot’ method around the drain to allow the weep holes to work correctly.
What exactly are you trying to do?
If I use a round-grate 3-piece Oatey ABS tile drain, is it possible to unscrew or screw-in the grate barrel (after the 2nd layer of dry pack mortar) when laying the tile, if needed to make the grate level with or slightly lower than the top of the tile?
Thanks.
Yes it is possible and is the exact reason the barrel screws in as it does.
Great job on this Website!
I assume polymer modified thin-set mortar absorbs moisture. If so, won’t sheet membranes such as Schluter Kerdi allow some moisture penetration, as thin-set mortar is used to attach and seal the sheets to the to-be-tiled surface? Or is the amount of moisture so minute as to be irrelevant?
As Redgard forms a continuous waterproof surface, this does not appear to be an issue for RedGard. However, detecting and covering pinholes is an issue, though your interesting method of a 1st primer coat of diluted Redgard followed by 2 regular coats should reduces that risk.
Is it possible to get Redgard too thick? If so, what is the impact on my tile?
Thanks.
Hi Allen,
All mortar will absorb some amount of moisture. I’m unsure where you are talking about that being a problem, I’m assuming at the seams. If overlapped 2″ per specs the water simply cannot penetrate beyond a certain amount. There is no space between the sheets with mortar between them. It is, instead, the two edges directly against one another with the mortar filling the open (microscopic) pores of each sheet and adhering it to the other. When done correctly static pressure will not allow water to penetrate.
It is possible to get redgard too thick, but it would take a hell of a lot of it and would not negate nor negatively affect anything other than building up the corners in your shower. If not evenly applied you will have some areas thicker than others.
Thank you for your time!
1) Concerned with tile or tumbled stone not adhering long term to cement board that has been top-coated with redguard. How long has this product been around to know if it might peel from the cement board over time, or the thinset peeling off from it, thus the tiles/stone fall off? We are looking for a ‘waterproof” application that also stand the test of time.
We have actually had an experience with being able to peel the redgard off some areas of the cement board (no tile up yet). We had suspected that the chap who painted on the redgard put it over dusty boards, so it did not adhere properly. We just ripped the whole thing out due to that and other issues.
2) we had considered painting redguard on the back of the cement boards before installing, intending to prevent moisture penetration beyond the cement board and allowing the cement board, thinset and stone tiles to ‘breathe.’ from the surface.
Any suggestions or comments related to this would be greatly appreciated.
Hi Lisa and Joe,
1) If the cement board was properly cleaned (wiped down with a damp sponge to rid it of excess dust and debris as you’ve stated) and primed as I’ve described above it will last as long as you want it to be there. If you were able to peel it off it is due to one of those two issues. The dust needs to be eliminated and the pores of the board need to be sealed. Redgard and other Elastomeric membranes have been around since the early 1980’s and are a proven waterproofing method. When installed correctly they work exactly as they should.
2) Painting redgard on the reverse of the boards would effectively negate all the advantages of a topical membrane – mainly the ability of the shower to dry out more quickly and the backerboard not becoming saturated. If you want to do that you may as well simply use a vapor barrier – that would be the exact same thing, a waterproofing, then backerboard, then tile. It would also be much cheaper. Correctly installed redgard will prevent moisture penetration beyond the back of your tile rather than beyond the cement board – that’s the advantage.
Redgard is designed to be an effective topical waterproofing membrane. When installed correctly it creates a completely waterproofed surface for tile installation which will last longer than a normal barrier/backer installation. I can not emphasize enough that EVERY shower I have torn out in the last eighteen years due to a failure of some sort was always due to incorrect installation, procedures or incorrect product application (using the wrong product). When installed properly these products work as advertised – if they didn’t there are a hell of a lot of really good tile contractors that would let everyone know.
Please don’t let the fact that someone installed it incorrectly the first time jade your view of the product – it’s a good product. It simply needs to be installed correctly.
Good. We will definitely use redgard on the face of the hardiboard- what you say makes a lot of sense!
I’d like to get back with you with a few more questions before we hire someone again. I hope that is ok. Thank you for this blog and for taking the time and energy to do things right.
Not a problem at all, I’ll be around here somewhere. Just look for the ears.
We built a shower curb with 2 2x4s and covered it with hardibacker but it seems short. Can we put another piece of hardibacker on the top to make it taller? We are going to cover it with Red Gard.
Hi Sharon,
Absolutely you can. You can install as many layers as you need to get the correct height as long as it is all redgarded and waterproofed correctly.
Hey Roger, One more question about the exspansion & contraction. I asked you in my last email that i had put two boards together without the gap between them. My question is, you say to leave a gap between them for exspansion & contraction or the tiles may pop off. My question is, what is the difference if you leave them together fill it with thin set & tape it or if you leave a gap, tape it & fill it with thin set. It still will be one solid piece. Thanks again. Bob
Good question Bob!
If you do not leave a gap, when you tape and thinset the seam the two individual boards will only be locked together by that very thin layer of thinset over the face of them. When you leave a gap and fill it with thinset it locks the two boards together with a layer of thinset as thick as the boards themselves. This means that the edges of the boards – every millimeter of them, will be locked together rather than simply a thin layer over the face.
Hey Roger, i am getting ready to start laying my marble tile & i have three questions. I have one place in my shower where the durock are touching & i have already taped & mudded the seams. I was wondering if i should run a concrete saw thru it to create a 1/8 ” gap & re-mud & tape or leave it alone. #2 Is it better to do the walls or the floor first? I was thinking the walls so you do not get a mess on the floor. #3 Since i have to polish the edges, is it easier to do it after they are layed, but before grouting or before they are layed? Thanks again for all your help. Bob
Hey Bob,
1) Unless it is a significant amount of the edges touching – like more than three feet of it – then you can just leave it and it should be fine.
2) If you have the time it is better to do the walls first. It doesn’t really matter, though, more of a personal preference. Always protect whatever you are tiling above whether it has tile on it or not.
3) Always polish the edges first before installing them. Whenever you install a tile it should be in whatever shape and finish it will remain.
Love the advice I’ve been reading. We have torn out an old shower. Hardibacker has been secured to the studs on top of a preformed shower pan (KBRS Quick Slope) . I’m ready to mesh tape and thinset the seams and corners. We plan to use Red Gard over the pan, walls and curb.
1) It is a strange shaped shower (base looks like an ‘L’) so we have an interior corner. Would you use mesh tape and thinset the corner or use a plastic corner?
2) We have extended the Hardibacker outside the wet area (there will be a glass wall to stop the water) which meets up with old drywall. The Hardibacker 1/2 inch is really less than ½ inch so it is not flush with the drywall. How would you recommend finishing this? Do I need to use tape? Mesh tape? Or just fill the gap with some mud? We have not decided how far over to take the tile. Should we finish the tile on the hardibacker then mud over the rest of the hardibacker to make the wall flush with the drywall?
3) We just built the curb using 2x4s and are thinking about putting a solid surface on top (to avoid grout on top) and tile the sides. Do we put hardibacker on all three sides? If so, should we mesh tape and thinset the corners? Should the top piece be a cap for the side pieces, or should the side pieces extend over the ends of the top piece?
Hi Sharon,
1) Mesh tape and thinset will be fine – no need for a plastic corner.
2) Use mesh tape and mud on that transition. You can build it up enough to even it out where the tile doesn’t cover. It may be easier to do that after you tile just so you have a nice, clean edge.
3) Hardibacker does need to be on all three sides. The mesh tape isn’t necessary but if you mesh tape and thinset it that will make it much easier to redgard it. It will give you a nice, smooth surface for the redgard. Put tile on the sides first, then cap it with your solid surface.
Dear Elf:
What a wonderful resource, thank you so much for being willing to share your expertise in such an informative, accessible, and entertaining format.
My wife and I are having our bath/shower surround redone in the next few days and we have some questions about materials/techniques. Materials: HardieBacker substrate, Mapei thinset mortar, RedGuard moisture barrier, Lowes white ceramic sub-way tile, Mapei Epoxy grout.
We understand from prior posts here, when using RedGuard it is detrimental/unnecessary to install plastic vapor barrier between the wall framing and substrate, can you advise/confirm? Should we use 15# builders felt instead, reasoning is, that unlike plastic it is semi-permeable. Note, RedGuard is our best option due to our contractors inexperience with Kerdie systems.
When using RedGuard, should we use Epoxy grout or standard mortar grout; we fear the combination of RedGuard and Epoxy grout could cause moisture to become trapped behind the tile due to the impermeable nature of Epoxy grout? Note, we have an older cast iron tub that does not include weep holes.
We have read on some forums that RedGuard and Epoxy grout can chemically interact, what is your experience/suggestion? Note, due to unavailability SpectraLock in our area, we are using the the recently re-formulated Mapei brand of Expoxy grout.
Any guidance you can provide us, would be very much appreciated.
Thank you,
The Swafts
Hey Gunnar,
When using redgard you DO NOT want a barrier or membrane behind your hardi. You always use one or the other – never both. (It can trap moisture between the two membranes.)
You absolutely can use epoxy (as far as the moisture concern). Any moisture getting back to the redgard would not dissipate through the grout lines – but it didn’t come in that way so it would be minimal anyway. If your tub does not have weep holes you can leave them open in the silicone or grout between the tup and tile at the bottom. I usually leave them on each side wall about an inch out from the corner. This is simply a space about an inch long in the joint (between the tub and tile) which is left open rather than caulked or grouted in. This will allow a space for any excess water to drain out from behind your tile.
I have never had a reaction with redgard and epoxy. That said, I (now) only use spectralock and have not used the new mapei formula – the old one did not react with it at all. If that is a concern you should call both mapei customer service (they’re friendly) and bonded’s cutomer service (they’re friendly, too) and ask that question. I doubt there would be a problem but it never hurts to check.
Hope that helps.
Hi Roger.
We have a standard tub/shower tile (4″ tiles) surround that needs to be replaced. We plan on using 4″ tiles again. One contractor ( a 60-70 year old with a great reputation) uses “old-fashioned” felt, mud/sand, and wire mesh behind the tile (those are the materials his tiler uses – an older Italian gentleman) ; says he’s never had any leaks with this method. 2 younger contractors (also with solid reputations) say they use redguard and also haven’t had any issues with leaks. I have tried and tried to find info comparing the 2 methods. Right now I’m just confused. This bathroom is upstairs in a 30-year-old house. We had a very slow leak from somewhere around the tub area onto the den ceiling below. I don’t want that to happen again, so I sure want to use the method that will last the longest and be the least likely to result in water leakage over time. What thoughts do you have about one method vs. the other? Are they both equally good, or would one be better than the other in this situation? Thanks for your thoughts!
Hi Diana,
The two methods work equally as well if they are done correctly. Neither is foolproof and requires someone with experience to be correct.
The redgard method is quicker, cheaper, and is a topical waterproofing – so your substrate won’t see any moisture at all. The redgard needs to be installed on cement backerboard or a similar product – not drywall. And it needs to be thick enough to be effective (about as thick as a credit card). That requires at least two coats and normally three.
The other method is called ‘mudding’ and it is absolutely, hands-down the most solid way to build any shower installation. I have torn out mud walls in a shower that were – literally – seventy years old and never leaked once. The waterproofing in this method is the ‘felt’ or tar paper. This is known as a ‘cleavage membrane’ and keeps any moisture in the mud walls from reaching your framing. Once any moisture gets back there it will run down into your tub. It requires someone with experience – period. If that contractor actually prefers that method it means he’s experienced with it. Anyone who is not would never, ever let you know it’s even an option. So if he uses that method he knows what he’s doing.
My recommendation would be to go with the mud walls if you can afford to do so. It is a better method and much, much more durable than the redgard method. It may be a bit of overkill but that’s rarely a bad thing long-term.
Hi Roger,
Thank you so very much for the quick and informative reply! I was leaning towards the “mudding” installation based on this contractor’s reputation, and it sure is nice to have solid information now to back up that decision. Your writing style makes things so clear and easy to understand. I really appreciate this!
Take care, and happy Thanksgiving!
Diana
Hi Roger,
Well, I chose the mud and felt method for the tub surround, but now I’m concerned. The felt paper and metal lath were installed today. The 2 inside corner seams of the tub surround were overlapped with the felt paper from the long back wall onto the 2 side walls before the metal lathe was nailed in place. Obviously, no greenboard was visible at all along those 2 vertical corner seams since the felt overlapped those seams. After the workers left, I went in to look at the completed work and discovered that the felt paper had been cut away at the inside vertical corner seams, so now there is no longer any overlap at all at the inside vertical corner seams and the greenboard is actually visible up to ~ 1/2 inch in some areas up and down the corner seams. The workmen are supposed to come back tomorrow to apply the mortar to the lath. These two young workmen are the 27 and 23 year old sons of the old Italian who apparently died last year. (I didn’t know this info when I first wrote to you; I thought the older gentleman would be the one doing the installation.) These young men worked with their father from their early teen years. My concern is that these inside seams are no longer watertight because the felt paper has been removed along those seams. Am I wrong? I’m going to talk with the contractor in the morning about it, but I wanted to ask you about it, too. Thanks for your help.
Hi Diana,
Those corners need to be overlapped to maintain the waterproofing of the cleavage membrane (the felt paper). Any idea why the cut it away? That doesn’t make any sense to me unless the corners aren’t totally square. Even if that is the case those corners need to be overlapped or waterproofed in some manner – you should not have open gaps in the felt, it defeats the purpose.
And if they actually worked with their father for that long they damn well know it.
Hi again, Roger.
Thank you so much for the info! I was glad to know that I wasn’t wrong about those seams needing to be watertight. I spoke to the contractor this morning, who said the same thing. Then he and I both spoke with the young workmen when they arrived. They don’t push the felt paper tightly into the corners as they put it up. As the lath is nailed into place, the lath pulls on the felt because it doesn’t fit flush in the corners. They cut the felt to relieve the pull at the corners. They said that they’ve never had a problem after cutting away the felt because the mortar itself in the corners is watertight once it dries. They willingly agreed, though, to put the felt back up so they reapplied the felt along the corner seams with the felt overlapping the walls a good 6 inches from the corners in each direction and then put the lath back over it. I feel MUCH better now.
I’ll have to ask them if their father cut it away at the corners. I’m curious now to know. Thank you so very much for sharing your knowledge and wisdom through this forum. You’re a jewel! Merry Christmas and happy New Year!
Hi Roger, you are very thorough but I still have some questions, even after reading everybody else’s questions. The installation directions for Hardibacker state to use a vapor barrier between studs and Hardibacker in wet areas. So….. since I’m redoing the shower, I put up vapor barrier on the three walls, then Hardibacker from the ceiling to about 1/4 inch above the topmost lip of the shower pan. Everybody I consulted with prior to this project said to use the Redgard, nobody mentioned vapor barrier, but Hardibacker said to, so I did, and now my walls are up (finally). Should I just skip the Redgard at this point, or should I paint it on corners and over the fiber tape? What about over the screw heads (I did use the recommended screws by Hardibacker)? Should I paint the Redgard up the wall to the height of the shower nozzle, but not to the ceiling or will that still create problems for trapping moisture? Should I take my walls down (ouch) and rip out the vapor barrier (ouch!) and then put them back up (ouch ouch ouch)?
I’m a bit confused about the very small gaps where the sheets of Hardibacker meet to form seams. Do I need to mud between them before laying the fiber tape? Then Redgard over the tape? I am planning on tiling over it all.
Also, do I leave the 1/4″ gap open/empty and tile down over the edge, so that the tile fits on the bottom lip of the shower pan and reaches over the gap to the Hardibacker wall?
I’m a bit confused about your recommendations for Redgarding the shower pan… My shower pan was entirely functional without any leaks, should I just leave it alone?
Thanks so very much for your help. I hate being a novice and the Home Depot tiling book is essentially useless (grrrrrrrrr). Melissa
Hi Melissa,
As long as you have the moisture barrier behind the hardi installed correctly there is no reason to use redgard. Redgard, being a topical membrane is a more effective system in that it will allow your shower to dry out completely between uses whereas the hardi with the barrier will retain water until it is flushed through with each shower. The barrier method, though, is completely normal and a tried and true method. So long as your barrier is installed correctly it won’t create any problems at all.
Yes, you need to mud between the hardi seams, then install the tape, then go over it with more mud. (Mud, in this case, being thinset)
The gap between the hardi and pan can be left open so long as your moisture barrier goes down over the flange and is siliconed along the back to attach it to the pan. If it does not then your barrier is not correctly installed. You need to ensure that moisture behind the tile has no way to get to the studs and only goes directly down and into the pan.
I only recommend redgarding the pan when the pan is fabricated from deck mud and tiled and your redgard is your primary waterproofing. If you have an acrylic or fiberglass pan that does not apply at all.
Don’t worry about being a novice – there are many ‘professionals’ out there that have never bothered to do as much research as you apparently have nor asked as many questions as you did. You’re doing just fine!
And yeah, most things about Home Depot are useless as far as tile is concerned.
I’m putting in a tub and fiber glass shower surround. I have already put up Durock on all three wall and want to make sure I don’t end up with the water damaged mess I was left by the previous owner. From everything I’m reading I should tape and mud the seams and then put the RedGard over top of that. My question is, is that necessary for my set up or is it all overkill? I’m not putting any tile up so the walls will be covered by the fiberglass surround to within 10 or so inches of the ceiling. Thanks.
Hey Brian,
You do not need to use tape and mud on the seams of the backerboard if you are putting up a fiberglass surround. You don’t need to use redgard either. Fiberglass and acrylic surrounds are both waterproof – no need to waterproof a substrate that will never see water.
The reason people run into problems with the surrounds and their substrate getting wet is due to the seams in the surround. Every seam should be siliconed to waterproof the surround. However, caulk and silicone are not made to be permanent applications – it needs to be replaced periodically. Once the edge of the bead is compromised – and this will happen over time – water will get behind it. Not only that but once water gets behind it there is no real way for it to dissipate quickly. A broken silicone seal will let water in but not back out nearly as quickly. The water will continue to migrate deeper into the seam and, eventually, into the wall cavity. All siliconed seems should be replaced at least every two years (if the shower gets daily use).
With that said, you can redgard your substrate if you choose – it won’t hurt anything. But if you simply regularly replace the silicone sealant in the surround water will never get back there.
Hey Roger,
I would just like to thank you for taking your time to do this. That is very generous of you to do this. My question is: I am doing my shower & i have put Durorock on all the walls & the floor & i would like to use the redguard for my walls & my shower pan. I have read everything on this post , but i am not clear about the Divot thing you are talking about w/ the drain. I went to the site that you suggested to go to w/ Robert, but i still do not get it. I have the durorock on the floor & the drain set. I do remember my plumber saying something about the weep holes when i was going to use a vinyl pan, but i am also putting a bench in it, which seemed to be a pain trying to put the vinyl on it & then today as i was looking for tile, i was told about the redguard & found your site. Could you please explain the proper procedure about the pan part & the weep holes? Thanks again & have a Christ filled day.
Bob
Hey Bob,
I’ll try to explain it as much as I can with words.
The 3 part clamping drain has three basic parts: the lower flange, upper flange, and barrel. Now between the lower and upper flange are weep holes (They are actually in the bottom part of the upper flange). In a normal shower floor the membrane is clamped between these two flanges. At that point water can actually seep into the drain from the sides of the drain – through the weep holes. You must have your waterproofing between these two flanges, whether it is a normal sheet membrane or a liquid. The barrel, the part that screws into the center of the flanges, when screwed all the way in sits a minimum of about 3/4″ above the upper flange. Follow?
Now, in a normal shower your upper mud bed, the part that the tile is installed to, is created above the waterproof membrane. So, when water saturates this upper bed and hits the membrane it will run down the membrane and into the weep holes – since the center of the drain is sitting 3/4″ above your membrane. When you use a liquid membrane you need to ensure that your liquid waterproofing runs from the top of the mud bed and down into the weep holes – hence the divot. The flat part of your shower floor runs all the way down, then about six inches around your drain a ‘divot’ is created to take the water from the flat part of your shower floor down into the weep holes. It is simply there to make sure that your weep holes are still located above your waterproofing.
This method is not necessarily for beginners – it takes some practice but it can absolutely be done. With that said you can also simply use the Kerdi drain and eliminate all these issues. Just install the kerdi drain and paint your redgard right onto it – it’s only one piece. That’s the absolute best way to go.
Hope that helps.
Hi Roger, you seem like THE only one able to answer that: I am doing a tub/shower surround. 1/2” Aqua-tough which is a CBU, on the walls and I plan to leave a 1/8” gap above the tub like you suggest. The tub is a crane peanut that has a double flange which basically offsets the tile 1” from the top of the tub.
After putting on the redgard so that it seals the seam between cbu and tub flange, and after putting on the tile, do I absolutely need a final caulking at the seam between the tile and tub? (I hate caulking and re-caulking every year, it is a rental cottage so a dirty caulk needs to be redone immediately). Will I be fine without caulking?
Many thanks!
Hi Sebastien,
IF you have the Redgard all the way down over the flange and IF that seam is sealed then no, you don’t need to use caulk at all. It is there to fill the space and ensure that any movement does not crack the grout (that’s why you aren’t supposed to grout changes of plane). A properly waterproofed shower does not need caulk for any mechanical or waterproofing needs – it’s mostly simply aesthetic.
Hi Roger, I am working on an old house that has an old concrete uneven floor in an upstairs bathroom with a lot of cracks. I’m thinking I will prime the floor with a concrete primer, then apply red gard in all cracks and let those cure. Next, I will apply several layers of red gard with a 3/4 nap roller to form at least a 30 mil layer. This will most likely take a few days. Next, I think I will skim coat the entire floor to level it as best I can with an 18 inch flat trowel and a flexurally sound thinset. Then, I will set my tile. Sound liike a good plan?
Hi Andy,
How out of level are we talking about? Your plan will work fine with a floor that is maybe 1/4 out of level over ten feet or so but if it’s more than that you would probably be better off picking up a bag of self-leveling cement (SLC) You simply mix it with water and pour it in there and it … wait for it … levels itself.
Much easier and quicker than what your talking about and given the price of good flex thinset it would be about the same. You can then set your tile right to the SLC after it cures.
Roger,
I used duerock on my shower walls up the first 6 ft. The remaining 2 ft i used greenboard For a total of 8 ft ceiling ht. Unfortunately i used plastic all around the shower under the duerock and greenboard. I still want to use redgard as that just more added protection. Do you think its a good idea? what about redgard on the cement board only? Or maybe just on the greenboard? what are your thoughts? Thanks Eddie
Hey Eddie,
No real reason to use redgard also but you can if you want to. I wold just use it on the durock as well as a couple of inches up the greenboard – just enough to make sure the seam between the two is sealed up. I shouldn’t be a problem as long as the top portion of the shower is left without a topical sealer.
Thanks for the info/hekp Roger. One other question. what would you recommend i use to fill the gap between the floor and the duorock? Thanks again
Hey Eddie,
If you have a traditional shower base (where the liner goes up the wall behind the backerboard) you don’t need to fill that space with anything. Simply run the tile from the backer all the way down to the floor.
If, however, you are using a topical membrane for the floor also you can fill that gap with silicone and install your waterproofing to that. If you have a traditional floor do not do this – it will seal the space where water needs to run down into the liner.
“Roger,
Im useing the traditional method. can the floor be redgarded? Thanks again for all your help.
Also, what gets tiled first in your opinion, floor or wall. I have heard many different opinions. whats yours?
Hey Eddie,
I usually do the floor first so I can stack the tile on top of it up the wall. I don’t always do it that way, but most of the time I do.
Hey Eddie,
You do not want to redgard the floor if you already have a liner in there. You’re gonna cause all sorts of problems if you do that.
Roger, I am inclined – after reading all the posts here – to use plastic or felt paper behind my hardibacker in a shower install as my water proofing membrane. However, I would still like to use Redgard to top my screws in my hardibacker and along seams and corners. What do you think of this? Any issues or counter recommendations? Thanks.
Hey James,
No real reason to do that but it will seal up the seams a bit better. Won’t hurt anything as long as you don’t seal up the entire wall – no worries.
Hi Roger,
My husband and I have gutted our bathroom to the studs and are ready to insulate and install the backerboard. Two of our walls are outside walls, the long center wall and the back wall. I have been reading about the redguard product and that you should not use a plastic vapor barrier to avoid trapping moisture between the plasic and the redguard. With that in mind, should we use unfaced fiberglass bats?? Am I correct in understanding that faced bats would be considered as having a type of vapor barrier?? We aren’t sure which to use. I would appreciate any advice.
Hi Paula,
Unfaced bats would be perfect. If you do get the paper faced bats they will work as well, just make one big slit down the center of it. The idea is that you need somewhere for the very tiny amount of excess moisture and vapor that will inevitably be trapped between the two layer to dissipate. As long as it isn’t sealed up air-tight (behind your waterproofing) you’re fine.
Thank you very much for your help; I really appreciate it! Been looking around your site since posting and it is a wonderful resource and will recommend.
Hi Rodger:
Great column!
I’m rebuilding an exterior bathroom wall with a soaker tub and a shower head. The tub is a cast iron Kohler tub with a with a 1/2 wide lip that rises a 1/4 inch.
http://www.us.kohler.com/onlinecatalog/pdf/1074694_4.pdf
At the bottom of this document is an expanded drawing of the rim flange detail (or lip)
Also, the tub was not placed flush with the studs on the exterior wall. In fact one side is 1/4 inch out and the far side is a 1/2 inch out from the studs!
1. When spacing the backer board, should I space it an equal amount out from the studs, ie keep the backer board in a vertical plane?
2. If equal spacing off the studs makes sense, by how much should the backer board be spaced from the studs?
3. The previous owner applied a cement like substance (thinset??) to the tub. How can I remove it without damaging the gloss tub coating?
4. Are there any performance differences between Redgard and Laticrete products?
Thanks,
Dee
Hi Dee,
Ideally (which rarely happens) the tub should be placed directly against the studs along the back (longest) wall. However, since you stated that it is 1/4 inch out on one side and 1/2 in on the other it leads me to believe that your wall framing/studs are not square – the tub is square. So, if that is the case you want to shim the board out from the studs on the part that is sticking out 1/2 inch by 1/4 inch. This will keep the board on the same plane (the same orientation) as the tub and will also square up the wall. Using 1/2 backerboard will give you enough width to be able to tile over the flange all the way down to the tub.
Get a plastic putty knife and scrape off that thinset (or whatever it is) and it won’t damage the tub.
For a normal shower/tub combo no, not really any difference between the redgard or laticrete products. That said, I prefer laticrete products over nearly everything else – it’s great stuff and laticrete stands behind their product insanely well! They are a top-notch company. If you have the choice go with Laticrete.
Boy, this is just about the best site I have come across in trying to get good information about my upcoming (first) tiling project! Unfortunately, I found it very last minute.
I have read all of your applicable posts, but I am still a little confused. I am tiling shower walls above a tub. This is what I think I should do to prepare for tiling–please correct me!
1. Fir out studs so backerboard will go over tub flange without bulging.
2. Install backerboard, leaving 1/4″ gap between backerboard and top of tub.
3. Fill gaps with thinset, fiberglass tape, and top with thinset. (Do I fill and tape the gap between the backerboard and the tub? )
4. Coat with skimcoat of redgard, let dry, follow with 2 more coats. (How long do I let the thinset cure first? and I bring the redgard down onto the tub flange, right?)
Please help! I’m actually starting the prep tomorrow…yikes!
Hiya Valerie,
1. Yes, fir out the studs so the backerboard goes over the flange without bulging.
2. Install the backerboard with a gap above the tub. I usually only leave about 1/16″. When you use redgard you want to be able to run it all the way down to the tub and any gap larger than 1/8″ or so is gonna be a pain to fill. Redgard shrinks when applied in anything but a thin layer on a flat surface. Trying to fill a gap with it will cause bouts of binge drinking.
3. Yes, fill the gaps with thinset, fiberglass tape, then smooth it out with thinset. Do not fill the space between the backerboard and tub with thinset. Different materials expand and contract at different rates, it will eventually crack and fall out. If you only leave a 1/16″ gap there it can be filled with redgard and still allow all the movement you’re gonna have.
4. After the thinset cures for 24 hours (the next day) you can apply the redgard. Mix some of your redgard with a 2 or 3 to 1 ratio of water (2 or 3) and redgard (1) and coat your backerboard with that. Backerboard is thirsty – it sucks the moisture out of nearly everything prematurely. Mixing up this ‘primer’ will allow the backerboard to suck the moisture out of the initial coat and the redgard will still be able to seal the pores. Then apply your two regular coats (straight redgard) as normal. Yes, bring the redgard all the way down onto the tub flange – you can paint it right onto the flange.
Relax, it’s just tile.
Roger,
Thank you so much! It seems crazy that there is so much conflicting information out there, but all of your info makes logical sense and just sounds ‘right’.
Do you have any special tricks for applying Spectralock? Do you think it is reasonable for a beginner to attempt an epoxy grout like Spectralock? I do have a friend who has done many tiling projects and is helping me, but he really didn’t want me to use epoxy grout because of difficult application. However, your site and the guy at the tile store convinced me to use Spectralock…
Thanks again! I wish there were awesome sites like this for every part of my remodel!
~Valerie
Hey Valerie,
Yes, there is a ridiculous amount of conflicting and incorrect information on the internet it makes me wanna puke.
As long as you follow the directions with spectralock in regards to the timing (first wipe after 30 minutes, second 60, etc.) it really is fairly easy to work with. I will usually leave out a bit of the powder part c (7% to be exact
) and that makes it a bit easier to work with as it starts to set up. The working time on the box really is the working time – no wiggle room there. If you can’t work with the entire unit at once within that time limit (and you probably shouldn’t try – nothin’ personal 
I have problems doing it at times) simply split up all the parts. Split them into equal parts by weight. The weight part is important – don’t do it by liquid volume. When I do split it up I usually just do half and half. You can do thirds or even fourth if you want until you get a feel for it.
Wow–that was a long day! My stupid walls were so out of plumb that I had 1-1/2 inches of shimming on the bottom of one! Then, the hardibacker proved ridiculously difficult to score and break, leaving me with a huge broken corner. Luckily, my screw gun battery died for good so now I get to go to bed. Maybe I will try a different backer brand tomorrow. No chance I can skimp on that thinset curing time before the Redgard, right…?
Thanks again for your help. Good thing I just bought a scale!
Hey Valerie,
That’s right. Unfortunately you need to wait for the thinset to cure before applying the redgard.
Roger,
Right now I am in the process of installing a new tile shower in my basement. I have an acrylic shower pan installed and I have put the cement board on the framed walls already. I did not put any plastic behind the cement board.
When I installed the cement board (permabase brand) I left about a 1/4″ gap between the edge of the cement board and the flange of the shower pan. The flange is 1/2″ just like the cement board so the tile should go over smoothly. Then where I have seems I left about a 1/8″ between the sheets. I wasn’t going to leave any gaps but after reading your article I decided it would be better. Now what do I with the gaps? I’ve heard that I should put silicone in the gaps. Then do I tape the seams or use a combination of thinset and waterproof mesh on the seams? Finally, I would put the red gard on. Do I take the red gard all the way down to the flange to make sure that seam is closed up really good?
Thanks for all your advice and help! It has helped me so much I really appreciate it!
Hi Jesse,
You do not want to put silicone in those gaps. The need for the gaps is to create a monolithic structure which all moves as one piece rather than each sheet moving independently. Silicone is for sealing areas to keep water out of them, your redgard is going to do that.
Fill and skim those gaps with thinset, apply alkali-resistant mesh tape (it’s just like fiberglass mesh drywall tape) then skim over that flat with more thinset. When cured this will tie each sheet into one solid unit. Take the redgard all the way down over your tub flange so that any water that gets there will run down into the tub rather than down into that gap and behind your wall. You can paint the redgard directly over the face of the flange so it goes nearly all the way down to the top of the shower pan.
Thanks Roger! The install instructions for the shower pan said to leave a gap because wicking can occur (which I assume they mean if water gets on the cement board it can expand up the board). Now I tried to always pay attention in physics class but doesn’t thinset have the same properties as cement? So I guess I’m wondering if that gap is filled with thinset couldn’t wicking occur still by going through the thinset and up the cement board? I’m just trying to understand the benefit of leaving the gap rather just resting the cement board right on the flange.
Then on the perma base instructions they say you should not leave a gap between sheets due to the edge tech it has. I already installed it and left a gap though.
Also, do I apply tape over the bottom gap or just put thinset in the gap only? I’ll put redgard along that bottom seam for sure. Then I’ll tape the joints. Do I tape the corners too?
Then I’m still on the fence as to painting everything in the shower with redgard or using a waterproof sheet like Kerdi. What would you recommend there?
Thanks for all the help! I’ve had a difficult time getting an answer from someone that I feel knows more than I do about this stuff.
Hey Jesse,
Yes, thinset is similar to concrete in regards to wicking. More than likely the reason the shower pan instructions state that is because most people simply install the board and tile – no water proofing or barrier. In that case the wicking will allow the water to reach the studs eventually. You can use tape on the bottom gap or fill it with just thinset – your choice. You should tape the corners as well.
With all that said – it’s all moot.
It sounds as if you’ve decided on using a topical waterproofing which, if done correctly, will not allow water to reach any of the board, thinset, or anything else back there. Once water hits your barrier it goes down and into the shower. It can’t wick if it never gets wet.
My preferred method of waterproofing is kerdi but it does have a bit of a learning curve. You may be better off with the redgard. I use kerdi for several reasons including time limits – I simply cannot wait around for redgard to dry before starting tile. You probably won’t have that issue so it’s probably your best bet.
Thanks again Roger. I believe I already understand this but I just want to make sure since I’ll be filling the gaps this weekend. I totally understand that the gaps in between the sheets need to be there to create a monolithic structure. My question still lies with the gap between the bottom sheet and the shower pan flange. That gap should be filled with thinset too? This is joining cement board to acrylic. That is where I thought the silicone should be applied. Also, it would be more work but I could always unscrew the bottom sheet and lower it down so it sits right on to the flange? Again, I will be redgarding the heck out of this thing too. Sorry for all the questions from this amateur.
Thanks!
Jesse
Hey Jesse,
Sorry, I’m brain-dead sometimes (unless you ask my kids – then I’m brain-dead all the time). You can fill that gap with silicone. You need something there to paint the redgard onto and continue your waterproofing all the way down over the flange – that way it always goes into the pan rather than behind it. Silicone will work, thinset will also work but you would lose the ability for normal movement between the acrylic and walls. Silicone will allow that movement and still give you a base for your redgard.
Before anyone else has an aneurysm – no, silicone is not necessarily an approved substrate for redgard. And no, redgard will not completely adhere nor bond with the silicone – it will probably leave streaks and be difficult to fully cover. However, silicone is completely waterproof, no? That is what we are trying to accomplish. I would rather have the combination of silicone and redgard there to allow for normal movement and have it be waterproof than have thinset covered with redgard there, which would still be waterproof, but would not allow for any movement.
You do not want to place the cement board directly to the acrylic pan, it would also not allow for movement and would likely cause problems down the line when things start to expand and contract. If you leave the gap and silicone it the movement can take place without affecting anything in front of it (your tile).
Never, ever worry about questions – it’s the only way to learn and I really, really wish more people would attempt that before watching DIY network and rebuilding their bathroom.
Roger,
I can’t thank you enough for all of the advice you’ve given me. I’m learning some life lessons here. I did not do anything with the gaps yet because I wanted to wait to hear back from you.
I have one final question on this and then I’ll stop bugging you. You mentioned that the redgard might not fully bond to the silicone…very good point. I have an idea. Since redgard is pretty thick what if I don’t use silicone in that gap and I just take a putty knife and load that gap with redgard? That way I know I have a really good seal and the redgard is rubber like and would also allow for movement. I know sometimes a contractor doesn’t have time to wait for things to dry but this is my home so I do. Even if I had to put on 3 or even 4 coats until the gap was filled I’d be okay with that. What do you think?
Thanks!
Jesse
Hey Jesse,
I think you may be putting on more than 3 or 4 coats. Redgard in anything but a thin layer over a solid substrate will shrink – a lot. It will work, don’t get me wrong, but it may be more of a hassle than you bargain for. I have been thinking about it (see, I don’t really have a life – just tile
) and I think a better solution would be to use a caulking backer-rod. This is simply a small rod of dense foam made to fill in large gaps before caulking or siliconing them. It’s so you don’t need to use a tube of caulk to fill in the entire gap and will only need to cover the backer-rod.
This would allow the movement and still give you a solid backing substrate on which to paint the redgard. You should be able to find it at a hardware or big box store (I know both Home Depot and Lowe’s carry it) and it’s usually only a couple of bucks. If I were doing it I think that’s the way I’d go with it.
And you’re not bugging me. I’m just glad I wasn’t the only one still thinking about it.
Great idea. I never thought of that. I’ll stop at my Home Depot. Thanks for everything!
Rodger,
I have another question. What should be done with the holes were the shower handle is and the shower head? Since you have to cut a hole where the shower handle is then there is some open space there. Should thinset and tape be put on fill that gap right to where the shower handle is and then redgard it right up to the rough in part of the handle? I was just thinking that if that isn’t all waterproofed then what is the point of waterproofing everything else? I hope I’m explaining my question correctly. Thanks for all your help!
Jesse
Hey Jesse,
You can tape and thinset up to the rough-in fixtures and redgard right to them. You can also place a bead of silicone around the pipes and redgard right up to that. There are several ways to seal them but yes, you’re right, they do need to be sealed or you may as well not bother with any of it.
Hi Roger,
I have a question regarding the silicone bead where the base of the backerboard and shower base come together. I realize this current thread is regarding a shower pan, but if this were a tub surround instead and you were going to put the silicone bead in the gap between the backerboard and the tub before applying the redgaurd, would you fill the tub with water like you would when tiling is complete and applying final caulk?
Hi Paula,
Yes, fill the tub with water first. This ensures that the tub does not move down and bust the bead of silicone when filled afterward. (But you knew that
)