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,
If one wall of my shower is an external wall and already has a plastic vapor barrier on the inside (clear plastic stapled to the studs), should I remove that prior to installing the cement board and coating with Redgard?
Thank you for the information on this site and your help.
Rob
Hey Rob,
Yes, if you don’t yet have the substrate up you should remove the plastic. The redgard on the face of the backer does the same thing for the wall cavity as does plastic behind it – without the whole ‘growing mold’ thing.
Roger,
Got it. Thanks again for your help.
Question regarding the process. Should I apply the Redgard before or after taping the joints and corners?
Hey Dan,
After you tape and mud it, let that cure, then install redgard.
Thank You
Anyone who reads this entire post should by now have a PHD in the application of Redgard for shower waterproofing!
Thanks!
Jon
I have a similar question regarding building a shower pan. I prepared the plywood subfloor with four coats of Redgard. Then I placed NOBLE Pro-Slope and a membrane above that. Next I am planning to place the hard packed mortar.
Was it a bad idea to prep the subfloor with Redgard? It seems like I am creating a membrane on membrane environment that you’ve described as potentially promoting mold. Should I redo the membrane and sub-floor or will the membrane be adequately sealed to keep all moisture out of the void between the Redgard and the membrane?
Cheers,
Derek
Hey Derek,
It’ll be fine. You aren’t sealing the entire perimeter around the redgard (on the subfloor) with waterproofing – there should still be open areas inside the wall cavity into which any vapor can dissipate. It wasn’t necessary at all, but it won’t hurt anything.
Thank you Roger!
Roger,
I just read your post about not using Redgard if there is a vapor barrier installed. Unfortunately, I read it after I installed my vapor barrier and Durock. I have not taped the joints yet, so would it help if I slid a utility knife between the cemboards and slit the vapor barrier, then coated with Redgard?
I mean “cement boards”
I would help tremendously if you did that. Although not ideal, it will be better than what you currently have in place.
Thanks for amazing information.
While framing for a pre-fab shower pan (32″x60″), I screwed the pan flenge to the studs with stainless steel screws. Had 6mil vapor barrier on the studs and then the Wonderboard (cement board) on all three sides of the pan with board just touching the upper lip of the flenge. Screwed with recommended screws, fill up the seams with mesh tape.
As I was planning to use RedGard to cement board, I landed onto your site recommending not to do so because it will trap the moisture in between. I understand the logic but wants to be safe than sorry latter.
Please advice my specific situation.
Thanks ….. Appreciate your time.
Hi Shahzad,
It would be best to remove the plastic – however!, you can leave it since you are that far along in the process. Make sure you give the thinset you used on the seams a couple of days to fully cure and made sure your walls are completely dry when you install your redgard. You don’t want to trap any moisture in between them. While not an ideal situation neither of us lives in an ideal world – sometimes you just have to make due with what you have.
Thanks Roger – You are awesome …
Roger, I came across the following product, which is much better than Redgard and cheaper by 50%:
http://www.prosol.ca/upload/pdf/176MapelasticHPG_TDS_EA.pdf.pdf
I used it and found that 1 gallons covers about 40 sq. ft.
What’s your opinion? Thanks.
Hi Shahzad,
HPG is fine, just not as good as redgard nor hydroban in my opinion. HPG requires fiberglass mesh reinforcement at all changes of plane – the others do not. HPG requires 4-6 hours between coats, 24 hours before tile, and 72 hours before a flood test, the others are under an hour between coats and tiling and about 12 hours flood test for redgard, two hours flood test for hydroban.
Any of these products, properly installed, work fine. Any of these products, improperly installed, do not work at all. It’s just a matter of what you’re comfortable with.
Hey Roger,
Im back with another question. Im installing a prefab shower pan. The opening Im working with is 48″x36″. I would like to install a 42″x36″ shower pan and then have a little bench (20″-24″ tall) right up against the shower pan. Have you ever posted anything on how to do this? (I realize its a rather specific question).
I assume (famous last words) I could build up the bench with 2×4’s and then cover that with Hardi board. Then redguard everything. Would the top of the bench need a slight slope? Would it be wise to head to get a piece of granite for the top of the bench as opposed to tile? Or is it just a poor idea in general to do this with a prefab pan? I wasnt really sure and I havent found to much helpful info on how to accomplish this online. THANK YOU!
Hey Steve,
You’re correct, just frame it out and cover it with cement board. Silicone the space between the flange and backer and redgard everything. The top does need to slope at 1/4″ / foot. You can use granite or tile, whichever you choose. As long as it’s properly waterproofed you can install anything on it you want.
Thanks!
Roger, Your site is great. Thanks for all the great help. Just a few questions.
Question 1, We have used a KBRS premade tileable shower pan on the floor and DensGurad on the walls. We are super concerned about water damage, so we plan on RedGuarding the walls. Should we just do the Densguard or carry the RedGuard onto the floor?
Question 2. How do you deal with tile thickness differences. We are using a porcelain 13″ tile and wanted to incorporate a glass mosaic to break up the pattern on the walls. However the glass is considerably thinner. Maybe 1/8″ – 3/16″ thinner.
Thanks in advance for the help.
Hi Jean,
1. Place a bead of silicone between the bottom of the denshield and the pan and paint the redgard down onto the pan about an inch or so. Nothing’s gonna go through that pan – no need for redgard there.
2. Like this: Setting different thicknesses of tile
Have a Shower that I finished in ordered to get my house done that I intend to turn into a steam shower. Have put Kerdi on walls , ceiling & used a kerdi pan. Have ceiling light in shower with Steam shower light pre installed. Didn’t use any Vapor barrier behind walls. Should I redguard the attic ceiling of the shower underneath the Insulation before inserting this steamhead ? Concerned about moisture getting around that light because every year ( my light fixture is in attic ( have to clean my light because some bug gets into and dies from the attic side. My light fixture lip was siliconed to the ceiling tiles according to the electrician who installed it. Is putting redguard on the back of that dura rock necessary? Is a vapor barrier necessary if I have the kerdi installed?
Hey Chester,
Nope, the vapor permeability of kerdi is around .053%, which means you don’t need a barrier behind your substrate. You’ll be fine with what you have there.
Roger,
I managed to get some silicone on the surface on my hardibacker. I imagine that Redguard will not sit to it, so my question is, should I sand the areas that have silicone on them before I start applying the Redguard. This is for a tub surround. Also, if I can leave the areas that have some silicone on them alone, will there be a problem with the thinset adhearing? Thanks in advance.
Dave
Hey Dave,
Thinset will not adhere to silicone. You can either sand it off or get a silicone remover, which is a liquid that essentially melts it and you can wipe it off.
that’s what I was worried about. Sigh. Thanks.
Roger ,I havehad to do a recovery of computer here is what I need you sent me information for a product that icould use to put 3/4″ solid hardwood 5″w on cement with out having to add 3/4″ osb or oter subfloor to nail could just put down with this product instead. Could you send me info again i have searched and could not find it
Thanks a million
Carol dawson
Hey Carol,
I think it was ThermalDry If that wasn’t it just google ‘wood flooring thermal break’.
Roger i found it it was bostik one step because my wood floor is 3/4″x 4 3/4″ wide myceiling is only 8 ft need all spacefor ntique furniture I have slabe home .i have been told ni could not do solid wood floor with out adding 3/4″ osbtonail down looks like besides being more wood to worry about it takes my vertical space .I LOVE the floor I picked out .I amso hoping this will work for me only water my home has had is dew to human error.
Thank you
Carol dawson My home is all above ground level
Hi Roger,
I am using a topical method for my shower walls using redgard. My question is where to stop the redgard near my shower pan? The durock will be applied over the pvc membrane. Do I take the redgard down onto the membrane or do I stop on the durock?
Thanks,
Hi Jason,
Take it all the way down to the bottom of the backer. It doesn’t need to touch the liner, but you should cover any exposed backer.
Thanks for the help.
Roger,
Thanks again for your various manuals! Major help!! Is this right, Im a new DIY’er and double and triple check everything (for installing a tile shower, topical waterprooofing, with a prefab shower pan):
The demo is complete. I’ll pad out the studs (because some of the existing utilites are proud of them) then install the prefab shower pan (nailing the flange into the padded out studs). Install the hardi backer cement board…now, heres my question…should the backerboard overlap the flange of the prefab shower pan…or, should it end just above the top of the flange? Either way, next I believe I would siliconne all around the joint between the hardi board and the shower pan (?). After this, mesh tape and thinset the joints (white, modified thinset). Then, Redguard all of the backerboard. Then tile with white, modified thinset. Grout and seal. Does this sound right? Thanks.
…oh, I would install the tile to overlap the the bottom of the hardi board (but above the lip of the shower pan flange)…then, fill that void in with silliconne. Then Im done…right? Maybe?
…sorry **(above the lip of the showerpan)**….not the flange. THe flange would be compeltely covered at this point.
Yes.
Hey Steve,
If you place the pan in there before shimming out the studs you will likely negate any problems with the lip. You can do it either way – above the flange or over the front of it. Then silicone the bottom to the lip and paint your redgard right down over it onto the lip. Everything else is correct.
Thank you!!
what are the advantages and what products do you recommend?
Hi Scott,
I recommend and use a LOT of different products. You’ll need to be a bit more specific.
Do you have a preference to Redguard or poly as waterproofing? Thanks.
…also, if one were to use poly and adhere the back of the poly to the face of the prefab shower pan…arent we then suppose to caulk between the cement board (after tiling) and the prefab shower pan when we are finished? Doesnt this trap in the wate that would run down the shower pan? Thanks!
AAANNNDDD, I just downloaded and read youre wall waterproofing manual (should have done that first
…I now have my answer. Topical.
Hi Steve,
Glad I could help.
If a traditional barrier is used the backer is not siliconed to the tub. When the bottom of the tile is siliconed there should be weep holes left in the silicone bead.
what can you tell men about paint on products that would serve as shower pan ?
Hi Scott,
They work as intended when installed as instructed. Some require fabric reinforcement, some don’t. Some need two coats, some need three.
I can actually tell you a hell of a lot about them, but don’t have that much time.
Anything specific you’d like to know?
Does faced insulation create a moisture barrier? I left the existing insulation inside the walls. I installed 6mL plastic over the wall, and on top of that I installed hardibacker. Is this an issue of 2 moisture barriers? thank you
Nope, no problem with that at all. It only becomes a problem when your substrate is sandwiched between them.
Roger – love your advice – the delivery is in good humor – to the point – and spot on.
Enough of the pleasantries – I do have a couple of questions as I am in the middle of rebuilding my shower
1) You said not to use a moisture barrier on the inside and a membrane on the outside so close together as they may trap water and cause mold in the cement board
What would you reccomend if it is an exterior wall and there is no moisture barrier from the exterior of the house into the shower (I’m told this is common in Arizona because it’s arid; it just sounds lazy to me)
I would think I need some moisture barrier from the outside? I’ve been told I must have a membrane on the inside? I wanted to do both – I trust you when you say don’t. Which one would Roger choose?
2) Would you say that having multiple moisture barriers on the shower pan floor would create the same water trapping/mold/evaporation issue?
Roger – you rock –
Hey Sean,
Sounds lazy to me also. I would use unfaced insulation in there, install the backer, then your topical membrane. The membrane inside the shower will still give you more of a barrier in that wall than the rest of your house if that’s how it’s built.
Multiple moisture barriers on the floor is worse than on the wall because the deck mud will continue to dissipate vapor over time. There’s already moisture in there – guaranteed, you’ll just be trapping it. Stick with one.
Roger,
I put in pre slope, put liner down and leak tested pan. When I drained the water from the leak test I have a small amount of water still on the pan. How much water would be acceptable? Should the liner be completely void of water when drained?
It should be. Is it in an area where you can peel it back and add more deck mud to fix the slope?
Ok – I should have read this first.
What do I do if I already used silicone in the gaps between my Hardiebacker boards on a tub surround? I am Paraniod about moisture behind — I just had to replace half an enternal wall behind the tub because it rotted out.
I want to to use Redguard on top as a waterproof membrane.
What can I do to fix this?
Roger,
I understand work sceduke so no problem thanks thik I will go ahead with redguard.
Roger,
Iam about to startmy taping and floating to my bathroom hardy 1/2″ when i was fixing to order my granite counter topswhen i over heardatile personsay he isnot fan ofred gaurd because the red color will bleed through and iask him if he used a white thin set over thre redgaurd to install his tile and he saidlater down the time somhere the color still bleed through then added he only recomends the membrane orange incolor and put on with thin set like wallpaper or the green stuff said it does not bleed through?I want to knowyour take on this cuasei think i can exchange if ineed to as it it has not been open yet i have hadenough issues with out that happening to me.
Thanks
Carol Please answer soon
Once cured the redgard isn’t gonna bleed through anything. I don’t know who he was trying to talk out of what but not only have I never seen it – I’ve never even heard about it. I call BS. If you want redgard use it, I’ve used it under a lot of natural stone, including light travertines. If it doesn’t happen with a porous stone like that it sure as hell won’t happen with anything else.
Space bar. Just sayin’.
Oh, and sorry, I can only answer questions as quickly as my work schedule allows. Day job and all…
Hey, thanks for the quick response. Lifts a big wight off the shoulders!
Hey Roger,
I’m almost ready to install a 3/4″ marble slab to the top of my shower curb, with redguard surface. I saw that Liquid Nails has a marble adhesive. Would you recommend this, or are there others that you prefer? I can’t tell you how much I appreciate all of your help getting me thru this shower project.
Thanks,
MP
Hey Mike,
Still doin’ stuff the hard way, huh?
Don’t bother with the liquid nails. Use thinset. Once cured it’s never gonna go anywhere.
Thanks Roger………You Da Man !!!
Oh how I wish I had found your site sooner! I feel I have been led astray by tech support and tile reps. I had never used aqua defense or other paint on waterproofing membrains. I have just done a shower, pre slope, liner, 15lb felt vapior barrior on walls, cement board, all seam taped and mudded, mud bed. The walls are insulated with UN-faced insulation, so not to trap moisture.
Guy at tile store told of wonderful benifits of using aqua defense as extra protection. Checked with tech support at mapei, and they said by all means. I checked all the sorces I could, and did not find anything to say not to do this.
Soooo, now I have applied aqua defense to all the walls, and around the outside of mud bed to wall joint. I was getting ready to cover the whole floor, and now I worry about mold. Question, If the walls are waterproofed, how would moister get trapped in the cement board layer? Same question for floors. It really gets to me that tech support told me to use this as “added protection”. Now I am really screwed up. I hate to change methods, and have used the old method for years. What would you recommend?
Hey Glen,
Leave it exactly as you have it and you’ll be fine. The walls may trap moisture due to differential temperature condensation. However!, you have the felt barrier – not the plastic. Roofing felt is a peculiar creature. It will, at first, soak in just the tiniest bit of moisture. This will cause the pores in the barrier to swell shut and increase the water resistance. In other words: the more water it gets the more waterproof it gets. Really. With roofing felt if you have a double barrier it’s not NEARLY as bad as having plastic, which causes problems. So you will be fine there.
The floor, on the other hand, has open weep holes (I hope) between your mud decks above the liner. This is a way that water can get into the mud bed beneath your membrane on top. So just don’t put a membrane on top.
Thanks!