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.
I have a tub/shower surround where I needed to replace the fixture and tile up to the ceiling. It’s a brick/block house, and oddly the bathroom walls consist of 1/4″ drywall with 1/4″ cement/stucco on the interior walls. The exterior wall appears to be solely concrete. The shower has an exterior wall with a window. The cement all around the tub’s lip has degraded and now the lip is exposed.
My plan is to break out the interior walls where the cement has worn away and put up cement board the 2 interior shower walls. Then patch up the exterior wall with some quickrete, over the tubs lip. I’ll put redguard over the cement exterior wall, but not over the cement backer board. There I will just have some plastic behind it. Then tile all 3 walls.
Any thoughts? Also, have you ever heard of a wall that is part drywall, part cement (there are no nails or screws holding the cement up, it’s as if they lathered it directly onto drywall. It’s quite smooth)?
Hi Ben,
That should work just fine. What you have is a form of mud walls where the drywall is used as the backer for the mud. The problem is it sounds like the mud is too thin, that’s why it degraded. It should be at least 1/2″ thick.
Roger
I am preparing to tile the the bath surround in my bath room remodel. I have used hardibacker board for the tile area. Can I also use the Hardiboard for the area above the nontiled area as I wasn’t planning to tile to the ceiling. How would you finish the hardiboard if just painting it? can you just finish the seams with regular sheetrock mud and then prime and paint the remainder? Thank you for your nice website.
Hi Van,
Yes, you can use it everywhere. It can be finished just like regular drywall wherever you won’t have tile on it.
Hi. Thank you for your advice. My handyman applied Redgard to ALL of the green board in the entire bathroom.
I see on a previous post that this should not be done. Now what? Do I have to replace all of the green 
board? Can I paint over it…or perhaps wall paper over it? I cant dwell on how stupid the mistake was but instead I need to focus on how to proceed.
Now in the shower where I AM tiling…….there is cement board. Just to clarifiy that I am reading correctly……a special mesh tape should be applied to all seams……then plaster should be applied at the seams…..then redguard painted over the tape and plaster and THEN thinset and tile? I’m sorry to sound so clueless but I am trying make sure I understand what the guy SHOULD be doing. Thank you. I appreciate your knowledge and help.
Hi Celeste,
If you are painting then you need to replace the greenboard, you can not paint over that, it won’t bond.
Over the seams you need the alkali-resistant mesh tape and THINSET, not plaster. Yes, that goes over the seams, let it cure, then the redgard goes over it.
Hi Roger,
I’ve removed the shower insert in my mstr bath along with the commode and vanity. I found about 15 years worth of water damage to the one exterior wall in the shower (this is the wall opposite the shower head), from a poorly sealed screened porch addition by a previous owner to my 1988 detached house in the woods. I cut and replaced the soggy 5′-5′ section of plywood along with some sistered joists and properly sealed up the ingress point from the roof. So after that I really want to avoid future water damage, but don’t want to go backwards.
I installed a nice preslope on top of mesh that’s on top of paper.
Installed pan liner to code with 12″ up on the 3 walls and not a single hole in it.
Installed top slope
Installed a mix of Hardie backer and Durock because they didn’t have hardie backer when I started. Hardie is the bottom 20″ of 2 walls and the entire wall where the faucet and head are.
I used the correct gray mesh tape for the wall board joints and sealed up edges\corners (before taping) with silicone II.
I’m about to start with RedGaurd and I’m realizing the insulation I used on the one exterior wall came with plastic on it. I didn’t use extra plastic behind the wall boards, but I’m concerned this insulation along with RedGaurd could be a problem. The plastic is mostly tucked inside of the studs, but I’m sure there are some points where the plastic laid over the stud when I put up the wall boards. I really don’t want to pull my wall down and replace the insulation.
So, how bad it is to have this plastic covered insulation behind my wall boards?
Is there anything I can do at this point that would help prevent moisture buildup behind the wall? ie. some form of dry heat during showers, like a heated floor, heat lamp or heat fan maybe.
Thanks for any help or suggestions.
-Steve
Hi Steve,
Normally if it isn’t a full sheet covering the entire wall cavity as well as the complete studs it’ll be just fine.
Roger,
I am getting ready to place tile on my bathroom floor. I have 1/4″ hardibacker on the floor.
1) Can / should i use redguard to make the seams water resistant. I have large floor porcelein tile to use on the floor.
2) will the thinset mortar stick to the redguard well?
Thank you nice website. http://floorelf.com/wp-includes/images/smilies/icon_wink2.gif
Hi Van,
You can if you want to, no real reason to, though. Completely a personal choice.
Yes, redgard is chemically manufactured so thinset will bond to it. It does so very well.
Roger
Thank you a lot. nice website.
Hi! Is it okay if I use Redgard on my walls but use Durock membrane on my shower floor (I’m using Durock’s shower base)? If yes, how would I handle the overlap between the two? Just Redgard over a ortion of the Durock membrane?
Thanks!
Hi Ron,
Yes, to all your questions. You would just paint the redgard over the durock membrane.
Roger,
Thanks for having such an informational site without any shitty affiliations to anyone other than awesome tiling!
My question isn’t in regards to Redgard, but I wasn’t sure where else to put my question, so I’ll leave it here:
I’m tiling a 5’X4′ stand up shower. My substrate is hardi board, and I’m tiling up to the 8′ ceiling. I’m using 19″ X 19″ porcelain tiles (huge for walls I know) and I’m not sure what method I’m going to go with to adhere. Deciding between 1/4″ square trowel on the wall and putting a thick butter back layer on the tile, or putting up wire lath from the floor to ceiling (similar to heavy stone siding I’ve done in the past) and tiling up that. Both ways I would be moving up slowly, giving time for each coarse to dry so I can tile up. Just curious what you thought, if you’ve ever used that big a tile in a smaller shower?
Thank you in advance
Mike
Hi Mike,
Just go directly to the hardi. But you’ll need to use a larger trowel – at least a 5/16″, 3/8″ would be better.
19″ x 19″ tiles weigh the same per square foot as 12″ x 12″ tiles. They aren’t heavier, they just take up more room per tile.
Thanks so much for the invaluable information here!
I’ve got a shower that I am redoing, one side shower, other side tub. I ripped out everything except the tub and have been following your instructions. I’ve got a mud pan with liner and I’ve installed the hardibacker and I plan on using Redguard. I’ve mud and taped the seams using thinset and alkali resistant mesh. I formed the curb using bricks and stucco. Just learned that I need to mud and tape the hardi-drywall transition too, thanks!
A few questions.
1. What do I do with the gap between the hardibacker and the mud pan? Do I caulk it and then redguard over it onto the pan a bit?
caulk after I tile?
2. Do I need to bother with any waterproofing of the tub surround? Shouldn’t get wet unless my kids get crazy… I did use hardibacker anyway, what do I do with the gap here between the backer and the tub? Just leave it open and
3. Do I use Redguard over the curb?
Hi Lesh,
1. Nothing. Provided your liner goes up behind it as it should you don’t need to do anything with that.
2. If you don’t have a shower head in there you don’t necessarily need it waterproofed. Silicone between the tub and backer, then silicone the bottom of the tile as well. That is where any water will collect and can get back into the wall framing.
3. No, your liner should go up and over the bricks to create your waterproofing there.
Hello Roger,
I was wondering if it’s ok to use Texrite porcelain ts, standard grade polymer modified dry-set mortar over redgard to install tile. This will be used on 2 shower walls 6’x3′
Hi Sergio,
Yes, that will work just fine.
Hi Roger,
I’m about to replace my plastic shower surround with tile, and I came across your site in my desperate attempt to gather as much knowledge as possible before making any decisions. I want to install niches, and, as I don’t relish the thought of an additional learning curve on my first shower tile install, I’m leaning toward using Redgard to waterproof it. As my search progressed, I stumbled across Redgard fabric membrane. I was wondering if you have ever used this product and if you feel that it is a good option. I’m thinking that it would be a good thing to use to make sure that my niche corners, as well as the wall corners are properly sealed. Could you give me your professional opinion regarding this?
Also, if you do feel that this is a good option, could you give me some tips on how to install it?
Thanks.
Hi Bill,
Yes, it’s a good product. It is, however, nearly identical to kerdi. So it installs just like it, with thinset, once that cures you paint the redgard down over it.
Hi Roger,
I’d like to wish you and your family a Merry Christmas and Happy New Year. Thank you for your prior help on my shower project. I have another question I need your help with. After I finish the shower pan and before tiling, I want to Redguard both the walls (1/2″ Durock) and the shower pan floor. Putting Redguard on the floor seems like an extra layer of protection against moisture and the smart thing to do. Is this a mistake? What happens if I apply redguard to a shower pan that has a liner installed? Thanks, Scott
Hi Scott,
You could trap moisture and your weep holes may not work correctly. You can paint the redgard out onto the floor about two inches on the perimeter, but that’s it. In this case overbuilding is not a good thing.
Hi Roger,
First of all, great site! I’ve found a wealth of information on it so far.
I’ve been reading through this thread and am a little confused. If I read correctly, in a regular shower application, I shouldn’t put a plastic vapor barrier behind the backer board if I’ll be using RedGard on top (to avoid a moisture sandwich and mold). However, in a steam shower, I must put a plastic vapor barrier behind the backer board when using RedGard. Won’t a steam shower have the same problem with trapping moisture between the two barriers (plastic vapor barrier and RedGard) as a regular shower would?
Thanks in advance!
Sam
Hi Sam,
Yes, that’s correct. Liquid elastomeric membranes are not VAPOR-proof. So the manufacturers require a vapor barrier as well. You would have to ask them about the specifics of both membranes trapping moisture, I’ve never received a satisfactory answer to it – so I don’t use liquids to waterproof steam showers.
Aloha Mr. Elf,
In a walk-in shower, I have hardibacker, premixed thinset along with fiberglass mesh taped seams/corners then a wash of Redguard over. Ready to tile 2×3 subways. Now…about this whole ‘do not use premixed’ that I run across now and then. Really?!? I have just short of a 5 gallon bucket left of the premixed and mixing up stuff in an apartment is not easy.
Also, I have a horizontal stripe of clear glass tile which I need to put white behind, of which I have 4 gallons of ready-to-use white tile adhesive leftover that I planned to use.
Sigh, please tell me I can use what I’ve got in the way of thinset and adhesive.
Mahalo!
René
Hi Rene,
Yes, really. Thinset can emulsify when it is constantly subjected to water, which it will be. And it will likely never fully cure between tile and redgard. There is no such thing as ‘premixed thinset’, it is simply mastic with sand in it. I have no idea what ready-to-use white tile adhesive is, but you HAVE to use powdered thinset to bond glass tile to redgard.
Hello again Roger,
I have a prefab shower base and on the studs is drywall. I will be covering the drywall with kerdi membrane. But first I will be installing a 14″x25″ plastic preformed niche.I’m going to cover the drywall with kerdi. The niche has a 3/4″ wide lip on it with holes for screws into the stud framing. What is the best way that you recommend sealing around the niches lip and the kerdi membrane. Do I put a bead of silicone from the drywall to the niche lip then cover it with thinset and kerdi or completely layer the kerdi in the entire niche and will it stick/bond well to the plastic. Please lead me in the right direction and a leak free shower walls.
Thanks, Wayne
Hi Wayne,
Your best option is to kerdi-fix the kerdi to the perimeter of the niche. That will bond the kerdi and give you a watertight transition.
Can you use redlock on green board?
Hi Kelley,
I have no idea what redlock is. If you mean redgard then no, greenboard is not a proper substrate for redgard. You need to use cement backerboard.
Roger, I was going to used schleuter membrane for my shower and coat it with redguard. Now Schleuter wants unmodified thinset but the redguard site says to use modified polymer thinset. I am using 12 x 24 tiles with one sixteenth spacers – which is the best thinset (currently I have mapei unmodified). Thank you
Hi Dennis,
Either one will work fine. I would use modified on it.
Hi Roger,
If I am going to use Redgard, do I mud and tape my Hardibacker seams with drywall tape or the alkali resistant tape?
Brooke
Hi Brooke,
Alkali resistant mesh tape.
Hello Roger,
Great site! Just for clarity, you recommend taping and sealing the seams with mortar before rolling on RedGard? I was going to put RedGard on, then seal the seams with tape/mortar when putting the tiles up. I guess water could still get through the mortar at the seams, and with no RedGard behind it, it could cause problems.
Hi Dan,
Yes, tape and mud, let it cure, then paint redgard. If you do the redgard first you are relying on the bridge of the redgard over the backer, if it moves and splits then you WILL have problems. Redgard gets painted over the tape and mud once it’s cured.
Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.
So for a steam shower, you have to have both some plastic over the studs AND something like Red Gard on the cement boards?
Hi Ron,
For a steam shower you need a vapor proof barrier. With all existing liquid membranes that requires a vapor barrier behind the backer as well as the liquid over the surface.
Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.
Hi there,
Good blog. Question. I am doing a laticrete preformed shower pan and hydroban. Do you suggest installing with a roller, or a 3/16 trowel? I figure I would paint the corners, use laticrete anti-fracture membrane and then paint them on, then either do the roller or trowel for the main surfaces. What do you think?
Second random question. do I fill the divot around the drain with pea gravel afterI screw in the drain, and then put thinset over the pea gravel (and rest of shower floor) and start tiling? Or are one of those plastic weep protectors better?
Hi Tauran,
Of the two the roller is likely the better option. Pea gravel, then deck mud, then thinset and tile. You can use the weep hole protector if you want, they are normally too large to use with a divot, though (the ones I’ve used anyway).
Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.
Hi Roger,
I put a first coat of RedGard over Wonderboard (and thinset on the joints) in my laundry closet yesterday. I wanted to put on a second coat today but there are many cracks and pealing all over the place. Have I put it on wrong or is it maybe a defective batch?
Thanks
Hi Vico,
I’ve never heard of that. The only thing I can think of (short of a defective batch) would be something on the backer before you installed the redgard. Did you wipe it down well and let it dry before installing your redgard?
Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.
Thank you Rodger. Have a great holiday season!!!
Hi Rodger. TY for this great info. Quick question …….I am going to redgard my cement board (no plastic behind). My plan is to lay the top deck mud, then hang the hardibacker (1/8-1/4 inch above final deck mud) then redgard. My question is how do I fill that small gap between the final deck and the board?
1) If I don’t fill it won’t there be a chance of water sneaking in there and going from the cement board to the bare wood studs?
2) if I am to fill it do I use 100% silicone and redgard on top of it and carry the redgard a few inches onto to pan floor?
Or……
3) Would it be easier (and smarter) to lay the board before the final top deck mud (do I leave a small gap above the pan liner in this case?) and bury the board in the final deck mud then cover with redgard to “avoid” the gap mentioned above to have a solid surface for the topical regard?
Does this all sound right? THANK YOU !
Hi Ed,
I normally embed the backer in the top mud deck, leaving about 1/4″ between the liner and the bottom of the backer. Or you can hang it above the top mud deck, it just hangs there, you don’t have to fill that gap with anything, gravity takes care of the water that ‘sneaks’ up behind there. Your liner should run up the wall about 12″, so the bottom foot of your wall is waterproofed behind the backer, water isn’t going to run up your liner.
Hello Roger, I am building a shower stall that is roughly 9 ft long and 4 ft wide. One end is steam and the other end is a car wash. The problem is that about 5-1/2 ft of one wall and 2 feet of another wall are extremely well insulated exterior stud walls with appx 1″ of spray foam behind a layer of tarpaper behind exterior stone, with fiberglass batt in the stud spaces. There will be some plumbing with fixtures in some of the exterior wall stud spaces. I am concerned about a moisture sandwich between the interior RedGard and the exterior foam insulation.
Can you offer some advice?
Thanks in advance, Jim
Hi James,
In a steam shower application (if part of your shower is a steam shower then the entire thing needs to be built as a steam shower) you are required to have a vapor barrier behind your backer with a topical waterproofing membrane on the walls. Exterior foam insulation is not going to cause a moisture sandwich, but you need a vapor barrier back there anyway, so moot point.
Hey Roger – (me again) – this question is a bit off topic, but it’s the only place that seemed close: a follow-on to my previous steam shower question. Here goes: So, I understand the ceiling of the steam shower is to be Sloped at between 1:12 and 2:12 pitches to avoid drips collecting on a flat ceiling and raining down on the occupants (are there other reasons?) Coincidentally, a week before I was planning to frame my steam shower ceiling, I spent some time in a commercial Spa’s steam shower. It had a 2:12 pitch ceiling, however, rather than the drips running down the slope and (presumably) down the wall, the drips simply collected at the ceiling grout lines, and rained down on the occupants in nice straight lines. Don’t get me wrong, it wasn’t bad, but now I am failing to understand the reason for a sloped ceiling. Can you comment?
Hi James,
That is the only reason for the slope to my knowledge. Commercial spas are completely different, though, they get vapor constantly and it sounds like they didn’t have the grout lines filled enough if water was able to collect in them.
Hi Elf
After reading about niche and grout line matching I see a difficulty in deciding on niche framing if I choose to waterproof with Redgard ($40 vs about $150 for Kerdi).
So how can I calculate where to frame the niche opening so it might align with future grout lines before I waterproof the shower? I know you’ve shown the example of cutting the niche after you start laying the bottom tile course and using Kerdi to waterproof on the spot. Should I try something similar with Redgard? Trying to guesstimate grout lines seems difficult while staring a cement board right now.
When I built a walk-in shower during my recent house addition, I framed in the niche before I even put on the Hardi-backer. If you want to get it close to lining up with the grout lines:
1. Determine your tile pattern and sizes, then measure down from the ceiling, including the size of the grout lines you’ll have. Mark on the wall / studs where that would be.
2. Contnue to measure down from there until you determine the grout line which will line up with the top of the “floor” of the niche.
3. Then, you’ll need to raise the top of the niche by the combined thickness of the backerboard and the tile, plus the thickness of the mortar / thinset you’ll be using, which will be determined by the size of the trowel notches.
4. Then, lower the bottom of the niche by the combined thickness of the backerboard and the tile, plus the thickness of the mortar / thinset you’ll be using.
5. In order for water to properly drain out of the niche, make the back of the niche “floor” approx. 1/4″ to 1/2″ higher than the front, depending upon the “depth” of the niche. The slope of the niche “floor” should not be so steep that shampoo bottles, etc. won’t stand up.
Hi Laura,
You can do the exact same thing with redgard (cutting it out after you begin tiling).