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.
Installing 1 inch mosaic tile on shower floor. Floor has been prepped with redgard. Mosaic is a mixture of brown marble, tumbled marble and glass that is tan and taupe in color. We intend to use white thinset mortar -the kind we have to mix.
My question is – Is there any chance the redgard color will show thru the glass tiles? If so how can we prevent?
Need info immediately, please and thx.
PS : Concerning the mosaic tile (glass & marble) for shower floor -what grout do you recommend? Unsanded or epoxy? Do we need to add a non slip coating? Suggestions welcome.
My shower walls are going to be marble with unsanded grout.
Hi Julied,
There is a chance, but not if you install it correctly. If you’re worried about it skim-coat the redgard with thinset, let it cure, then install the tile. It will not show through the thinset, if that’s what you’re worried about, only in areas where you don’t have the coverage.
I am remodeling a shower and plan to use tiles over 1/2 ” durock on the three walls, but not on the ceiling. What is the recommended material and thickness for this application? If regular drywall should be used, what do you recommend at the joints with the vertical durock sheets? What about finishing; hydroban or just primer/paint? Thanks!
Hi Dave,
I assume you mean for the ceiling. Regular drywall is just fine with primer and paint on it. You can tape and mud the joints with mesh tape and thinset, it can be sanded and painted just like drywall mud.
Roger, Thanks so much for your site and the effort you’ve put into it.
Quick question re 1/8 gaps between hardibacker boards. You’ve said that you personally caulk silicone the corners. If I’m planning to tape the corners and seams with red guard & fabric / tape could I not just silicone the joint gaps as well and redguard them similarly. Having worked with elastomeric roof fabrics and coatings I’m much more confident in them handling future movement than the thin set & tape and it seems I could skip a repetitive step.
You can skip it if you want. Standards want them taped and mudded, but there is no tile police.
Then who are those guys who always come around selling tickets to the Tile Policeman’s Ball?
“Skip” is a poor choice of words on my part. I’m thinking more that with a 1/8″- space the silicone with fabric and red guard over will handle movement better than the thinset.
First use of red guard and fabric went very smoothy. Thanks for your advice on using it. Found it very similar to metal roof systems I’ve used in the past. It does dry much faster than I was expecting it too.
It will work, it’s just not standard compliant.
Applying 6×6 and 6×12 stone tile on redgard over hardy backer. My question is whether to apply the proper thin set direct to the hardy backer, direct to the back of tile, or both for best adhesion. Any comments will be appreciated.
Hi Jeff,
Apply it to the redgard, then backbutter the tile with the flat side of the trowel to fill any inconsistencies in the back of the tile. That will give you a full bond.
Thanks Roger
Hi Roger,
I am a contractor in Alaska and up here we install vapor barrier on our exterior walls to keep moisture the house from getting into the insulation in the exterior wall and condensating. With this in mind, how to you address a bathtub on an exterior wall where you cannot remove the vapor barrier and would like to use Redgard in a shower application? Thanks
Hi Chad,
It would completely depend on your local codes. You can leave the vapor barrier there and just cut slits in it between the stud bays if it’s allowed. That would keep the moisture from penetrating your insulation while still allowing for needed vapor dissipation. It it’s not allowed then just leave it. While allowing vapor dissipation is ALWAYS best practice, not doing it is normally not a deal breaker to the point where it will compromise your installation enough to cause significant problems.
Roger,
can I use redgard directly on shower tiles (ceramic)
Hank
Hi Hank,
Provided you rough up the surface of the existing tile it is approved for that application.
Hello Floor Elf,
A friend and I are tiling the walls and celing of a shower for the first time. Your website has been a lifesaver! We have durock installed on walls and ceiling and are planning to use RedGuard to waterproof it all. I was hoping to just tape the seams, then RedGuard, and then fill the seams with thinset at the time of tile application. But now I wonder if filling the seams with thinset needs to be done prior to the RedGuard application. What do you think? Thanks in advance for your help.
Hi Edna,
The seams need to be taped and mudded (with alkali-resistant mesh tape and thinset) and allowed to cure prior to installing the redgard. Otherwise your seams will not be waterproofed.
I gutted a bathroom and installed a new fiberglass tub. I used green drywall in the shower surround, used fiberglass tape on seams & primed the entire surround with Zinser Primer. I planned to use redgard over the primer then 3×6 subway tile over it. After reading conflicting opinions on the web, I’m not sure how to proceed. Am I going to need to wreck-out all of the work I just did & replace the green board with cement backer board?Can I use 1/4″ Green e-board over the surround & redgard over that? I’m confused.
Hi Steve,
The green drywall needs to be removed. It is not a proper substrate for redgard. You CAN install green e-board, or another backer, over the drywall, but it MAY lead to problems down the road. There is no real way to tell whether it will or not, but it CAN. That’s enough for me to tear it out. If you go over it with a backer you will have a 1/4″ lip on each end (vertically) which would need to be covered in some manner as well.
We have a 1 piece plastic tub/shower that was installed a few years ago. The shower head is about 14 inches above the enclosure and sometimes water splashes on the painted surface. I’m worried about long term water damage. I’d like to put a row of 12 inch tiles around the enclosure. I have no idea what is under the paint. Can I just use redguard over the paint and then use thin set to install tiles?
Hi Liz,
You can rough up the paint by sanding it, then install redgard and tile. It’s not a proper substrate for it, but it’ll work just fine over a tub surround.
Before installing on the painted surface, you might want to check its integrity before adding the weight of the thinset and tile. If it’s drywall, and water’s been splashing on it, make sure that it hasn’t been comprised / softened. The paint “should” be sufficient to keep water from directly contacting it, but might want to check, just to be sure.
My contractor used RedGuard on cement board for shower walls and have cast iron pan. The RedGuard appears to be weeping through tile grout after shower leaving “pink” tint in water droplets on pan. Still happening after 6 months. What happened? Is there a fix?
Thanks
Jim
Hi Jim,
I don’t believe it’s the redgard. A pink tint from water is more indicative of a particular (common) type of mold or minerals in the water.
I read through your manual on liquid topical shower waterproofing and had a question about the divot method you describe. Maybe I’m just dense, but if I choose to coat the entire shower, walls and floor, with a liquid membrane, why can’t I just create the mud deck all the way up to my standard drain (so the weep holes are covered with the mud up to the top of my drain) and then paint my liquid membrane right up to the top edge of the drain? If the liquid membrane is waterproof, I don’t care if there are weep holes or not because there is no way any water would get down there, right?
Don’t get me wrong, I trust you, and I’m ready to go drop $100 on a topical drain. It’s my own thinking (lack thereof) I don’t trust.
Hi Jared,
Because if and when the drain backs up a little the water will flow up the pipe and into the weep holes saturating your substrate beneath your shower floor. Given the right conditions (slow drain just plugged enough to not allow full drainage speed) the water would never actually back up out of the drain to the surface, only into the weep holes. You’d never know it until your shower floor rotted through.
$100 drain or the divot method is much cheaper.
Hi Roger, I am building a walk-in shower with a niche. I plan to waterproof it with red guard. I used durock and have taped and applied thinset to the seams, inside corners, and outside corners, including in the niche. My question is, do I need to use a fabric with the red guard on the corners in the niche since I have already taped and filled the seams with thinset? or can I just paint on the redguard without the fabric? Thanks!
Hi Brian,
You can just paint the redgard in there. It’ll be fine.
Hello! We are tiling the shower walls with subway tiles. We used the RedGard on top of the cement board. It has been red for over a month.
We are using Versabond Fortified Thin Set Mortar in White. My husband was
installing line 12 when two tiles from the 3rd row completely popped out and there was not an ounce of thin set on the tile, it all stayed in the wall. Could the RedGard be causing this? Any ideas?
Thanks
Hi Melissa,
No, the thinset is causing it. It is either not mixed correctly (not enough water), has set in the bucket too long (check and pay attention to open pot times on the thinset bag) or the trowel is not large enough.
Since using the Redgard eliminates the need for the plastic vapor barrier, how would I handle NOT having the plastic overlap the pan lip so water runs into the pan, not behind it? In other words, what do you use for the backerboard/shower pan joint?
Hi Eric,
If you are using a topical membrane for your floor then it is one continuous layer of membrane, no way for water to get behind it. If you are using a traditional membrane then the membrane runs up behind the walls three inches above the height of the curb and the redgard is painted all the way town to the bottom of the backer.
Well, my concern (using Redgard) is with the 1/8″ gap between the shower pan lip and the bottom of the backerboard, since I don’t want to butt the backerboard right up to the pan. Can the Redgard be applied over this sized gap?
Oh, a shower pan, sorry. You can fill the gap with silicone or caulk and paint right over it with the redgard. I would not span any open gaps with redgard, it will shrink.
Thanks! Sounds like the way to go….
Which should I use with Redgard – mastic or thinset. I’ve heard that using mastic will not work because the waterproofing prevents it from drying correctly.
Hi John,
That’s correct, you need to use thinset.
Hello and thanks for this post – I just found out all four bathrooms in my home were installed with drywall instead of cement board, so I get to update four moldy surrounds (yay!) I was wondering — two surrounds are adjacent to each other (i.e. the tubs are in different rooms but side by side against the same wall). If I apply redguard to one surround, should I still apply it to the other? It occurs to me that this might be akin to the vapor barrier next to redguard situation you were talking about, and could breed mold. Thanks!
Hi Ashley,
No problem, yes, install it on both sides. The substrate will not be trapped between the two barriers, there is a wall cavity separating the two into which moisture can dissipate.
I found plywood walls in my shower after I took off the old tiles!?! Do I cover the wood with thinset mortar then apply the Redguard? I’m told I can’t simply paint it on the plywood (even though a video says cardboard can be made waterproof!?!) Is it possible to put Redguard over the glossy tiles then put on the new tiles?
Hi Chuck,
You can not put redgard over the existing tiles. Cardboard can be made waterproof, but it doesn’t expand and contract like wood will. The problem is not making it waterproof, the problem is movement. The plywood needs to be removed and replaced with a proper substrate, in the case of redgard that would be cement backerboard.
We have an old house that has metal lathe and some kind of crumbling (could it be ancient tar paper?) flakey, dark brown stuff, covered with stucco. The floor was just poured concrete, and yes, it leaked out into the hallway. I am wondering if we can just Redguard over the stucco walls, and after fixing the stucco to fill in where the poured floor meets the walls, just redguard the floor too? In other words, keep things as they are with a coat of readguard for waterproofing? Thanks.
Hi Erin,
Yes, it is tar paper. You can repair the stucco and redgard it, but you’ll need to create a mud deck for the floor. There is no way to tie redgard into an existing drain in a concrete floor.
Yeah, I guess I was kind of hoping I could get around the demolition/pouring of a new shower pan. At least the walls are salvageable. I would prefer to coat the entire shower walls with redguard -does it matter if the crumbling (and I am assuming ineffective) tar paper is behind the stucco, since you advise that it is not a good idea to put reguard over an existing waterproof membrane? Does tar paper count?
Hi Erin,
No, it doesn’t matter. Yes, tar paper counts, but not if it’s disintegrating.
Can I use Redgard on drywall or is it only to be used on cemment board for a waterproffing membrane?
Hi Eric,
Only on cement backerboard.
I have hardiebacker and only applied the membrane at the board joints and at the drywall transition and whenever I have screws, is that enough for a tub surround or do I have to coat the entire walls. Thank you
Hi Adrian,
You need to coat the entire wall. Hardiebacker is not waterproof.
Hello Roger,
My question is this, if I’m going to redguard my hardibacker on an outside stud wall of my tub surrond what kind of insulation should I use in that wall?
Hi Mike,
Unfaced batts.
So, if I’m reading this right, if you do RedGuard, you still use a backerboard, but you do not use a vapor barrier behind it, correct?
Hi Lesh,
Correct.
HI,
I have Durock put up to the ceiling, is it necessary to apply redgard all the way to the ceiling? or only certain height. thx
Hi P,
It needs to be a minimum of 2″ over the top of the shower head. Anything above that is optional.
Im doing a bathroom remodel and replaced the tub with a new cement shower floor, i cement board the walls also already and sealed the joins with thinset. My question can i cover the whole bottom of the cement shower floor with redguard. i have a water membrane on the bottom of that cement thats the way my contractor did it. i live in Florida
Hi Rene,
If you already have a membrane in the floor you don’t want to put redgard on top of it. You can paint it out from the walls about two or three inches, but you don’t want to cover it.
does that mean that I can pour a slope pan right on top of my hardie backer floor and redgard over the pour and I’m good? thanks for the post, I found the whole thing very informative.
Hi Mike,
It requires a proper tie-in to the drain with the topical membrane (redgard) but yes, a topical floor is simply a single slope with the membrane applied.
wow, what a fast reply! In order to properly tie the redgaurd into my three piece drain, what should I do…just roll the redgaurd around the bottom flange on the three piece drain? Thanks!!!
Nope, it takes a bit more than that. Google ‘shower floor divot method’. I don’t have anything written up about it yet.
Ok, will do. Thanks for such prompt replies, and for having this resource available. I have done a bit of web research on tile, and your posts are the clearest, and most concise, that I have seen.
I want to use Redgard over a new slab addition where the concrete seams meet. Can I use cement based self leveling products over the Redgard in thin layers? I guess my question is regarding bondability. I am using a bonding agent before the self leveler. Also when applying thin-set over Redgard should I not use the notched trowel side to aviod puncuring the Redgard membrane? Thanks Earl
Hi Earl,
I don’t quite understand why you want to use slc in thin layers. slc needs to be poured to the height you want in one pour. You should use the notched side, you won’t puncture the redgard.