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.
Roger,
Yet again, I request your input. Due to my poor planning, I’m in a holding pattern working on my bathroom renovation. On one wall, I removed a window and it’s going to take over a week for the glass block guys to check it out (it’s in the shower). The other two walls in the shower are ready to be Hydro Ban’ed. Can I spread the Hydro Ban on the two parallel walls, leaving the intersecting wall un’spread (the one with the window)?
I’ve never worked with the stuff before, and I don’t know if the bond would be compromised if the membrane isn’t applied at the same time.
I just want to finish this darn project already!
Hey Russ,
You can Hydroban anything you want to and leave it. A new coat will bond to it just fine. It doesn’t compromise anything to have a cold seam or joint in the hydrobanned walls.
Hi Roger,
Our new shower is being built. Its size will be 67″long x 35″wide.
The pan is made of Plywood. Two walls will be glass and two walls will be built with densshield. I have purchased 2 gallons of HydroBan. If I understood correctly, once the tile contractor will have done its first layer of mud (mortar), we could cover the pan with two layers of HydroBan instead of installing the clumsy rubber membrane. Then the contractor would do its second layer of mud and we would apply another two coats of HydroBan. As well, I suppose that we would need to seal the densshield joints with HydroBan. And how about the existent ceiling made of plaster (house built in 1955). Should I apply a coat of HydroBan on it and cover with primer & paint?
Am I heading in the right direction?
Hi Yves,
That’s not quite correct. When the first layer of deck mud is down and sloped you paint the hydroban on it and that’s it. The tile is installed directly to that layer. Topical methods eliminate the need for a double mud deck. The densshield seams normally get sealed with silicone, but you can do it with the hydroban if you want to. Unless your shower is an enclosed space (it has a header across the entrance) there is no need to waterproof the ceiling. If it’s not being tiled a good latex paint will work fine.
Hi Roger,
My husband and I are re-building a shower in the basement. We have completed the pre-pan, installed the mositure barrier about 12 inches above the floor and put in the final shower pan. We have installed Hardibacker on all the walls. There is no vapor barrier behind the hardibacker with the exception of the one for the pan. Shoud we use redgard after we tape and mud the seams? Also, should we use thinset in the corners with mesh tape or should we seal the corners with silicone caulk? Thanks!
Hi Mary,
Yes, you need some sort of waterproofing on your backerboard. Redgard works well. You should tape and mud the corners.
Hi Roger –
Thanks! Also – We have a curb that was made using 2X4’s and then a plastic “cage” which we packed with michigan mud (same stuff we used for the shower pan)….should we also paint the redgard on the side of the curb that is inside the shower (or should we do both sides and the top?) or do we just need to do the hardibacker because the curb already has the moisture barrier that comes up the middle? Thank you in advance for your answer…..You are saving us a huge headache!
Hi Mary,
Both sides and the top with the redgard.
Our contractor is installing a tile shower for us and we noticed that the dark forest green colored liquid waterproofing membrane that he used on the cement backer board is peeling off where he had used tape to hold some tiles in place. He didn’t seem concerned at all but I went online to research this and found your post about NOT using a plastic vapor behind the cement backer board when you use these type of products. Our contractor/friend did use plastic sheeting and I am now very concerned since a leaky shower was the reason for the complete $$$$ remodel to start with. He has the shower floor done & grouted already but has just started the walls. I’m really concerned about this and considering tearing the whole thing out (or at least the walls) and starting over rather than risk a mold & moisture problem down the road. Any thoughts on this?
Hi Ann,
I wouldn’t worry about the tape pulling it off, tile will never place that type of pull on the walls. Tape also puts stress of the entire tile on one very narrow area.
The barrier behind the backer does not guarantee a problem. It’s simply one more step to take to minimize the possibility of a problem. Provided the surface waterproofing is installed correctly there should never be a problem in respect to the double barrier.
Hi Roger,
Am I correct that what Ann is talking about could be considered a mold sandwich as you have mentioned in the past? If not then what is the difference? Thanks for all your input and expertise.
Paul
Hey Paul,
Yes, that is exactly what she’s talking about. And as I stated, a problem is not guaranteed, it’s simply another step to prevent problems.
Do your books have instructions about the floor drains? And I want to add a seat or more of a bench and I have seen a bench installed of solid concrete blocks mortered together, to the wall and then tiled over. Have you ever heard of such? Would ther be anything wrong with this?
Hey Mike,
The manual you bought does have specifics on the drain, both the topical drain as well as utilizing the regular drain with the divot method. Benches are covered in the design manual, but more to do with the tile layout on them. There are just too many different ways to build one to cover everything.
Yes, you absolutely can build your bench out of cinder blocks, it’s done a lot. Build the bench before installing your shower floor, otherwise you’re trying to build a level bench on a sloped floor. Just bond them together with thinset. If using liquid waterproofing just paint it right over the cinder blocks and install your tile to it. Treat them just like the wall. The only thing you need to ensure is that the top of the bench is sloped to allow water to drain.
Some websites show creating a threshold into the shower by screwing together 4 2X4’s together into floor and folding the waterproofing membrane over it. Can this be used to waterproof the threshold/slope made out of wood 2X4’s instead? Thank you for your time!!!
First timer,
Michele S.
Hi Michele,
Yes, provided you are using redgard for the waterproofing of your entire shower floor as well. If you are using a rubber membrane to waterproof your shower floor then no, you can not end the membrane at the curb then waterproof the curb with redgard. The membrane must be one piece up and over your curb. If you do use redgard you need to cover the 2×4’s with cement backerboard, you can not apply it directly to the wood and tile it.
My project is re-tiling a 3-Wall shower over tub. My cement backer-board joints are meshed and grouted and I’m ready for RedGard. I left a 1/4″ gap between the bottom of Durock and top of the tub. Should I fill this gap with Redgard, Silicone sealant or neither? I was planning on using silicone sealant here but also use it to caulk the bottom edge of tile to the tub. This seems like it would trap water.
Hey Andy,
You need to silicone that then use the redgard over it. You need a solid, sealed transition from the durock to the tub. When you silicone your tile to the tub you need to leave weep holes so it will drain.
I am redoing my master bath and carefully removed the tile to find floated concrete walls. I never had any leaks before and the tile was removed with an air chisel. Would it be ok to tile over the existing concrete substrate? This is a second floor shower with what appears looking through the drain to have a hot mopped pan. What about coating the enitre surface with a red gard type product for added piece of mind?
Thanks
Hey Dave,
You can do either. Provided the mud is in good shape you can tile right over it. If you use redgard only use it on the walls – not on the floor also. If you’ve never had any leaks and you haven’t touched the membrane it should be just fine.
Hi Roger,
I’m renovating my upstairs bathroom mostly by myself. While knocking out the long wall of tile behind my tub, I found an old window. I plan on removing it and sealing it up but have been told 20 different ways of doing so. It’s sealed from the outside (condo complex, someone obviously cheaped out on doing it right) and is covered with vinyl siding already. Should I spray-foam in where I remove the window, sealing it with a sheet of plywood cut to size (with holes drilled for expansion obviously)? And then what do I insulate that wall with (exterior wall)? Roxsul? Also, should I put a vapor barrier over the insulation before boarding up with cement board (denshield), then paint the redguard on over the denshield, and tile directly over that? I also have a 5″ roll of kerdi/ditra to use in the corners-do I stick this on the seams and apply the redguard directly over top?
Any help would be greatly appreciated. Thanks, eh?
Hi Jennifer,
Wow, you have about three different types of waterproofing there for one little old shower.
You should install the plywood then plastic or some sort of vapor barrier directly behind it in that window space. As far as insulation whatever you have in the rest of the wall will work fine, as will spray foam. Do not place a barrier behind the densshield – if you are using backerboard install a barrier. Densshield is not a backerboard, they are two completely different materials. Densshield is waterproof, backerboard is not.
As far as the face of the substrate and waterproofing method I’ll need to know which of those products you’re using.
Hi Roger,
So I will remove the window, and can either use roxsul or sprayfoam to fill in that hole. Then I will insulate the rest of the wall (it is an exterior wall) with roxsul. I will most likely use denshield as the backer for my tile, and will apply the redguard overtop of that, with the kerdi/ditra in the corners/joints under the redguard (the 5″ strip rather than buying mesh tape as I already have the orange stuff). My question is, being here in Calgary, do I put vapor barrier behind the denshield as it is on an exterior wall? Not sure if I’m being clear of if I’m confusing myself!
You do not need vapor barrier behind densshield. Densshield is a waterproof substrate, you only need to silicone between the boards as you install them and silicone over the screw penetrations. That’s it. No need for redgard over the face of it, no need for kerdi as banding. You can use it all if you want, just no reason to. It will work.
My contractor has finished my bathroom remodel (walk-in shower) up to the point of tiling. He used Denseshield for the walls and then Redgard. Two questions: Contractor did not mud and tape the seams or corners before applying the Redgard. Talking to others, this is not good. Can he cut through the Redgard at the seams and mud and tape over the Redgard? Will Redgard installed to the proper mil thickness be OK without mud & tape?
Hi Lori,
Although not ideal it should be fine without taping and mudding. As long as the redgard is at the proper thickness it also acts as crack suppression, which means it has flexibility to it.
When taping the backerboard with thinset you should use alkali resistant fiberglass mesh tape that is made for CBU and not regular drywall fiberglass mesh tape. Thinset is highly alkaline and corrosive which deteriorates regular drywall mesh tape. Especially so in wet areas like a shower. The CBU tape is coated with a polymer that is alkali resistant
Roger- I’m about to put backerboard up for my shower but the studs behind the ends of the tub are aways back from the tub, maybe as much as 3/4″. In order to get the backerboard hanging over the flange around the tub, can I hang plain old drywall on the studs, then backerboard over that, followed by Redgard over the backerboard? Thanks!
Hey Ben,
No, but you can hang strips of drywall over the face of the studs, or just regular wooden shims, to bump the backer out where you need it. You can also shim it out enough to have the face of the backer flush with the face of the flange and stop the backer right above the flange and silicone that gap. Then install your redgard.
Good deal. Just for clarification though: hang drywall strips horizontally or vertically? (Or does it not matter?) Because I’m the curious type, I’m also wondering why strips and not a sheet. Is it because a sheet would restrict air/moisture movement?
Again, thank you!
Vertically over the face of the studs. Basically making the studs deeper. A full sheet may trap moisture, and we all know what drywall does when it’s wet.
That’s right – it causes your dog to burst into flames!
I have tore out a three foot shower and a garden tub in my master bathroom , I have deceided to install a larger shower with shower heads on both sides , one wall is an outside wall where there was a window that was above the garden tub, that window was taken out and I had glass block installed in its place . Now for my question …I installed plastic on the studs for the outside wall and also on one interior wall , the other interior wall I built using 2 X 6 lumber . I installed a membrane liner for the base along with a curb . I then installed 1/2 inch backer board on all three walls , I don’t want to have a sandwish mold problem in the future . Do I still need to seal the all the joints on the backer board ? or since I used the plastic on the studs am I ready for tile ? Thanks Tom , Carmel Indiana
Hey Tom,
Yes, except for the one wall without a barrier behind it. You did not mention whether you are using redgard for your waterproofing or you’re using the aforementioned plastic as your waterproofing. If you’re using redgard you should remove the plastic. If you’re using the plastic you need to add plastic to the third wall as well. The joints in the backerboard need to be taped and mudded (with thinset) regardless of which you choose.
If you are simply asking whether you need to silicone the corner which has plastic behind it – yes, you still need to do that.
I only have concrete backer board up 3 feet around the shower then greenboard to the ceiling. Is it ok to use Redgard on the greenboard or will it delaminate or hurt the integrity of the paper on the greenboard?
Hey Herb,
Redgard (or any other liquid membrane) is not approved for use over any type of gypsum board. You need to have cement backer all the way up to two inches above the shower head. I honestly don’t know what it will do. I’ve torn out one shower that they bothered to use redgard in, over drywall, and it peeled off like a sticker. The gypsum inside the drywall was wet as well. I believe the paper and gypsum suck the moisture out of the redgard and it never gets a good cure or bond, but that’s simply pure speculation on my part. I do know that in that one shower I tore out it was not effective.
Hello,
Over the weekend I installed backerboard for my three shower walls. Today I learned on the internet that I shoud have stapled roofing felt to the studs as vapor barrier. My heart sank at the thought of tearing all this off and puting up the felt. RedGuard shoud save my butt, Right? I have one exterior wall and two interior walls. All have insulation. Any suggestions or reassurance would be awesome.
Thanks so much.
Dan Dueker.
Hi Dan,
Yes, redgard will save you.
You have a properly prepared substrate to install redgard over.
Hi guys,
Not to be a party pooper here , but in your article above Roger, you stated that it was imperative that two moisture barriers not be so close together. You did specify plastic & redguard being on each side though. So, are we to assume that roofing felt is ok ? I was thinking of doing the same except I was going to use Tyveck behind the cement because of it’s breathability.
Thanks,
Mike
Hey Mike,
The problem derives from having redgard on one side of a substrate and ANY vapor barrier directly against the other side. This sandwiches the substrate between the two. With the barrier against the back of the exterior wall, as you would have on an exterior wall, you have a wall cavity between your two barriers. Moisture can dissipate in there. If it’s directly against either side of the substrate it traps it.
My wife wants a shower installed in her bathroom that only has a tub now. Sounds pretty easy huh? Problem is there is a large 48″ x 40″ greenhouse window located 28″ above the tub. The window is wood and 21″ deep. She wants it tiled from tub level to the ceiling and all around the window, including the inside of the window. Any ideas on how this can be accomplished? Can Redguard be used to waterproof the window after a sloping base is built? I can’t seem to come up with a safe way to put a shower in without removing the window. Any suggestios are welcome.
Hi Will,
If the sill and outer frame of the window are wood then you can just replace it with backerboard and use redgard on it. If the muntins (grids) of the window are wood then you’ll need to replace them or the entire window.
Hi there:
I’ve done everything that you have suggested, including using the mesh tape and thinset to smooth the seams on the cement board. Unfortunately, some of my walls were not level, so I ended up applying the thinset all over the walls to even them up, hopefully making my tile installation much easier. Once the thinset dries, would you suggest I still use two coats of RedGard?
Hi Jilly,
Yes, you still need that thickness to waterproof your installation.
Roger,
How do I waterproof the floor side of the shower curb? I will be using Hydroban on the curb and ditra on the floor. I asked Laticrete and they said “We don’t have any testing data for the compatibility of Schlutter Ditra and LATICRETE Hydro Ban.”
Hey Jerry,
Install the Ditra first, fill the cavities along the shower, let that cure, then paint the hydroban over it. As long as you have a continuous layer from the floor up onto the side of the curb it’ll be fine.
Dear Elf – I’m getting ready to do my master bath shower. The handyman wants to use Densshield; I like the idea of RedGuard. Can I use both of these together to create a good waterproof shower stall?
Thanx –
JC
Hi JC,
You can, but it’s honestly ridiculous. There is absolutely no reason to have a double layer of waterproofing with two different products on your shower wall. If one doesn’t do it then it wasn’t installed correctly. If either of those are not installed correctly it may end up being counter-productive and your shower won’t be waterproof at all. Installed correctly either of them will create a good waterproof stall. If you are paying the bill, and you want him to use redgard, have him use redgard.
Redgard is made specifically for installation over porous surfaces – densshield is not that, it’s waterproof. It may delaminate.
Just wondering if I can use the kerdi membrane on the backerboard joints and corners then use the redguard over top. I have a roll of 5″ kerdi that I would like to use up instead of mesh.
Hi Troy,
Yes. It’ll do the same thing and be a better option.
Ack! Maybe I read your posting too late. I thought I was being really smart and thorough waterproofing my tub install. I put Aquabar “B” paper behind the backer board then did a real spiffy job with tape and thinset on all the seams. Then, to be sure I was totally waterproof, I decided to Redgard the backer boards. Brilliant!
Unfortunately, I can see now that if water gets behind the Redgard there’s no escape and I’m asking for mold. Everything is solid and well installed, so the last thing I want to do is rip the backer board off the walls and start over. If I make a few weep holes around the perimeter of the tub is there a good chance it’ll be ok? The bottom of the backer is untreated and open to drain into the tub from behind the tile.
Thanks for your help! I think I’m close but don’t want to make some serious error and have to start from scratch in a year.
Hey Van,
Just make sure you have weep holes in there and they stay open. Since the backer is unsealed at the bottom you’ll likely be fine.
My father was remodeling my bathroom and stopped (due to work) before he could finish tiling the shower and floor. Now it is up to my husband and I to finish the job. I have read your blogs regarding niche installation and waterproofing, which we plan to follow. Currently we have concrete board in the shower. My dad used regular paper tape and on the wall seams. Is it safe to use the RedGard over what he has done? We do plan to use the fiberglass mesh tape installing the niche. Also, I noticed on your niche instructions you did not explain how to build the shelves inside the niche. My plan is to build a long (2-1/2′ – 3′) skinny niche next to the corner of the shower and have a couple of shelves within the niche. I’m almost certain the shelves just fit within the niche side tiles and slanted for the water, but I want my shower to be done correctly and cannot afford to guess.
April
Hi April,
You’ll need to remove the paper tape, it will become debonded then you’ll have hollow areas behind your tile. You are correct, the niche shelves just tuck into the tiles along the sides of the niche, those lock the shelves in and support them.
thanks for the laughs, more so for the information. condo built in 69 and nothing is right! everyone kept telling me to put some darn board up. only they are not paying for it all. to do that cost way to much, it also ment calling in a plumber to bring pipes out farther so I could tile. really hope that this day an age, well there just had to be a RedGard. Thanks you really saved this poor mom alot of money and hair. I do thank God for craftmen like yourself. You know the ones that don’t charge for every bit of information. A true craftman shares, THANKS!!!
So in my shower area, I’ve finished putting up a vapor barrier (plastic sheeting running down the studs into the shower pan), concrete backerboard, mesh tape, thinset in the backerboard joints, and now I’m tiling. I stumbled on your handy guide to shower niches, and decided I now want to add a couple niches (I’ve only done one row of tiles, so I can make sure the niches follow the grout lines — don’t want to get yelled at!) but I’m unsure of the best way to waterproof them. From what I understand, Redgard will work, but I don’t exactly want to buy a gallon of Redgard for two 9″x12″ shower niches… unles I have to! What would you suggest? Also, what kind of tape do you use with the Redgard (maybe I missed it above)?
Hey Jake,
Redgard is your best bet. You may be able to find some kerdi cheaper than the redgard. Just the regular mesh tape that you used to tape and mud the boards with is fine.
When waterproofing a shower with a liquid membraine do you apply the waterproofing to the floor as well as the walls?
Hi Cole,
It depends on how you’ve decided to waterproof the floor. You can, but it takes special considerations with the drain and a couple other items. If you have a regular liner in your floor for waterproofing then no, you don’t install it on the floor also.