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.
Hi Roger. I live in southern NM (dry climate) and am in the middle of my first bathroom remodel. We bought a house built in the ’80’s and were aware of problems in the master bath upon purchasing the home. I ripped everything out of the bathroom and found some pretty significant water damage to the framing around the shower and tub, including an exterior wall. I cut out what I could of the damage and framed it back in with pressure treated wood. It looked like the tile walls were regular Sheetrock and there was no apparent vapor barrier, just LOTS of caulk in the shower (and some bulging tiles).
Needless to say, I was pretty freaked out and am now worried that I may have gone overboard with waterproofing. I did some reading before starting the shower rebuild and decided to hang plastic sheeting from the studs behind my durock. The thickest sheeting I could find was 3 mil and all of the employees at the local hardware stores had no clue what I was talking about. I used roofing nails and hung the plastic.
During my installation of the durock, the plastic sheeting got torn to hell, so I decided to buy Aqua defense and paint it over the durock and shower floor before installing my porcelain tile. I finished taping/thin setting the durock joints this evening and planned on applying the Aqua barrier tomorrow or Friday…then I came across your post. After reading it I really wish I hadn’t installed the plastic sheeting, and believe the Aqua defense alone would have been far superior. Should I consider ripping out my durock and starting from scratch? Or do you think the holes torn in the plastic during durock installation might help to mitigate the chance of mold in the future?
Thanks for your time, and a big THANKS for your website!
Hi Branhan,
I think it’ll be fine with the AD over it. You just don’t want the entire wall cavity sealed up. You need someplace for vapor to dissipate. The holes in it will allow that.
Hello – I am working on installing tile shower enclosure with a niche. I was planning on using plastic sheeting as a vapor barrier and redgard on the niche. Will this be an issue? As the plastic sheeting will not be fully sealed behind the wall since it will need to be cut out around the niche. Thanks!
Hi Kyle,
No, it will be fine. When you cut out the hole for the niche silicone the barrier to the back of the backer around the perimeter, then paint the redgard about two or three inches out onto the wall once you get it built.
Hi Roger, Thank you so much. I was wondering, how do you clean brushes after using red guard? I don’t want to use a great brush if it is better to throw away the brush after usage. Also, if paint is going on the ceiling of the shower, does that mean I can not Red Guard the ceiling? Should I just Red Guard the walls? …and Third, is Red Guard Stinky?
Hi Mori,
1. I use disposable brushes. You’ll never really get them clean enough to use for anything else.
2. Yes, if you’re painting the ceiling do not redgard it. Paint won’t stick.
3. It depends on what you consider stinky.
It does have an odor, but it isn’t bad and dissipates rather quickly.
Dear Roger,
I’m DIY installing a (4’x7′) steam shower in my home. I am planning my ready-for-tile surfaces as follows:
Walls: –>Studs/Plastic*/Durarock/Silicon-Mesh-Thinset Joints/Hydroban
Floor: –>OSB/Roof felt/Pre-slope/PVC/Deck Mud/Hydroban
*The plastic layer in the walls was recommended by some steam retailers due to increased vapor from steam
Questions:
a) Do you recommend a different configuration?
b) If yes, do any of your available manuals reference steam shower specifics?
Sincere regards and thanks in advance for any advice,
Dean
Hi Dean,
The plastic layer is required with elastomeric membranes in a steam shower.
1. I would not have both in your shower floor. Just the pvc is sufficient (and the one necessary to create overlap with your plastic over your studs). The hydroban over it may cause drainage / water retention issues
2. Yes: Laticrete steam shower technical manual
Hi Roger,
I found this Steam Shower video from Kerdi.
https://www.youtube.com/watch?v=Z7F0eEnS4BU
I am hoping you have a few minutes to view it, if you haven’t already seen it. They are using Kerdi Board on the walls and ceiling, but they aren’t using a second layer membrane or any kind of RedGard-like product. I am thinking of following this approach, but I was hoping you could provide your sage advice, since I am sure they are a bit one-sided in their viewpoint.
If the link doesn’t work, you might try going to youtube and searching for “Kerdi Steam shower”. The video is actually called “Kerdi Shower Systems – Steam Room Installation”
Thanks for all you do for us half-@$$ed do-it-ourselfers.
Hi Jim,
Kerdi-board can be used in a steam shower without a secondary barrier. The perm rating of kerdi-board is sufficient for a residential steam shower.
I want to convert my bath tub that is tub only to a tub/shower. I have to extend some tile work above the existing. I want to use redgard. How can I check to make sure that the current drywall above the existing tile does not have plastic membrane behind? I want to prevent the trapping of moisture.
Hi Josh,
If it’s drywall it doesn’t matter. If you’re going that route without replacing the drywall with cement board then it makes no difference if there is plastic behind it or not, the drywall at the bottom of the shower will eventually be soaked and disintegrate from water running down the wall.
Roger, we are doing the same thing with our tub..creating a shower. We have 1/2″ drywall with a 1/2″ of plaster over it. We plan on using backer board to the ceiling and then coating it with Redgard and then setting tile with mortar. Do we need to worry about any kind of membrane behind the drywall? The house was built in 1960. Right now they have Marlite (horrible stuff) on the walls so far up. We will be tearing that off.
Behind what drywall? Do you mean backerboard? If you are using redgard then no, you don’t need a barrier of any sort.
Actually, I want that we don’t know if they used any kind of moisture barrier underneath the sheathing (or siding). Should we worry about that. We would have to remove the siding, etc. to figure that out. What if we drilled holes in the top plate to let any moisture in that outside wall escape, in case they did you a moisture barrier on the exterior wall?
help!
I have a 75 sf shower surround and I put on three coats of aqua defense two days ago, but only used 1 1/4 gallons and it doesn’t look like credit card thickness. the container says it covers 60 sf. do I need another coat and since I was messing with the walls do I need to wipe them down first.
thanks roger
Hi Christine,
Yes to both. Let the walls dry after you wipe them down.
If we are pouring our own shower pan, how long after pouring it until red guard can be applied?
Hi Kathy,
Three full days.
Hello,
We know we have cement board on our shower walls, we are unsure if we have plastic behind the cement board. We would like to use redguard to waterproof prior to tiling. What would you suggest we do, cut a hole in the cement board to confirm if plastic was installed? And if there is plastic there, what would you suggest that we do before we put the redguard on. Or would you recommend that we don’t use redguard if there is plastic?
Our shower is an exterior wall.
Thank you
Hi Mary,
Are all your shower walls an exterior wall? There should already be holes cut in your cement board, unless you don’t have any water controls in your shower.
Look back there. If there is plastic it should be fine, if not use redgard.
Can Redgard be painted? The shower walls will be tiled to the ceiling but the ceiling backboard is not being tiled. If Redgard is used on the ceiling, will the surface be uneven or will the redgard reject painting? If it can be painted, what type of paint should be used ?
Hi Dennis,
No, it can’t, the paint won’t bond to it. But the backer can be finished just like regular drywall.
Hi Roger,
… another steam shower question: How do I seal anchor mount penetrations (like grab bars or hand-shower mounts) in a steam shower?
Thanks again,
Jim
Hi Jim,
Once you drill the holes through the tile to attach them fill them with silicone before installing the fasteners. The screws will seal the hole as you drive them in.
1. I used hardibacker for the a bathroom reno. I used Redgard to waterproof the walls. I have been reading, after-the-fact of course, that Redgard does not adhere well to hardibacker. I also missed missed the step in the instructions where it said to wet down the backerboard before applying Redgard. I have only put on the first coat of Redgard but I am now wondering if I will have issues down the road with tile falling off since I am using hardibacker and I didn’t wipe down the walls. Do I need to peel all the redgard off the walls and start over with applying a 4 to 1 mixture of redgard first, then apply the rest of the redgard at full strength or do you think it will be okay to proceed with the second coat?
2. For the shower niche used the Schluter kerdi band and Redgard to cover the seams and waterproof the niche. Now that it’s dry I can see a few air pockets. Should I remove the kerdi band completely and start over, or can I cut out the section with the air pocket and add an new piece of keridi and cover it with Redgard?
Thanks so much for your insight. My research has left me confused and not sure of the best direction to proceed.
Hi Deb,
1 a)No, tile will not ‘fall off’ of your walls. b)Ideally yes, you should have at least wet down the backer, but that is to remove any excess dust or debris from the backer first. c) Removing it depends on how easily it peels off. If you try to peel it and it comes off in very small strips then it’s likely just fine. If it comes off in 6×6″ squares or larger at a time – remove it and start over.j
2. You can cut out the places with the bubbles and just paint redgard over them.
Hi Roger, I have your install guide for the Kerdi membrane. Thank you! I am at the part where I am water testing the shower. So far (after about 4 hours), there is no noticeable drop in the water level, but I do see a few small dots on the floor, where it is discolored, presumably where water has penetrated a very small hole in the Kerdi. (I can send you a photo if you want.) All of them look to be where there was a small grain from the dry pack mortar bed that has been perhaps stepped on and maybe ground into the Kerdi. So my question is … If I still see no noticeable drop in the water level after 24 hours, are these pinprick holes a problem, and if so, what should I do about it?
Hi Allen,
Those normally aren’t a problem at all. You can always spread a little kerdi-fix over them if you want, that won’t hurt anything. If you’re as anal as me you can always place a patch over them as well. (I would not bother with that in my house, I would always do it in a client’s house)
Roger,
Your site has been extremely helpful. Thank you for putting things in normal language. I am remodeling my tub/shower. I installed 2 niches and was referred to use Kerdi strips as means of waterproofing all corners inside and out of the niches. Well, I thought I had it all flat,smooth, and perfect, but when it dried I see there are some spots where the Kerdi strip is raised and has an air pocket under. Can Tile over this? Also, would you recommend using redguard in addition? Thanks
Hi Zack,
You can either put more thinset beneath those areas and tile over it (at the same time) or cut out the raised portions and redgard over the seams. Either one will work just fine.
Hello Roger,
I am using a Kerdi drain and redgard for the shower floor how much of the drain do I cover with the redgard ? thanks for your help!
Hi Craig,
The entire top portion with the fleece. All the white should be red when you’re finished.
Roger- Great site and full of helpful tips. Thanks!
I have hung Hardiebacker in the shower and have silicone caulked the joints.
I am about to tape and mud the joints now. After that dries (24hrs) I was going to redguard the the joints. I know I read to redguard the whole shower, but I have heard that redguard and the Hardiebacker will not bond with each other. Do you know if this is true?
Also, would I need to use a Membrane Mesh with the redguard at the seams, and especially around the shower niche areas?
Thanks again!
Hi Andy,
I do know if that’s true. It is not true. It is bullshit.
Yes, with redgard it requires mesh reinforcement at changes of plane, but not at the seams if they are already taped and mudded. Always a good idea to use it around niches as well.
How high up the wall do I have to put the Redgard? Its says my one gallon will only cover 35 feet and my shower is 50 feet. Can I just use the redgard for part of the shower that actually takes water?
Hi Erica,
Your waterproofing must go a minimum of two inches above the shower head. And you need the proper thickness, not just a single layer over the walls. You will need more redgard. The 35 feet is with the proper mil thickness.
I was planning on applying Redguard to my shower walls before going out of town for the weekend so it can air out a bit as the bathroom is adjacent to the bedroom and I remember the Redguard stinking up the place the last time I used it. I was then hoping to start tiling the walls two weeks after that. When I called Custom, they recommended tiling right away (as soon as the Redguard was dry) as dust, etc. could get on the surface. In your opinion, is it important to not wait more than a day or two before tiling over the Redguard?
Hi Linda,
It will be fine provided you clean the redgard off with a sponge and let it dry before tiling.
Would you use redguard on on your bathroom floor? I have cement backer board down so I would be painting it on top of the backer board. I am not expecting a lot of water on the floor but I thought the crack resistance might be helpful for the tiles that I will be laying. thanks
Hi Bindy,
Yes, that’s what the product was originally designed for.
Roger,
I really appreciate this site – so much great information!!
I remodeled a shower last year and applied Redgard to the walls. I’m remodeling another bathroom in the house this year and it shares a wall with the shower in the other bathroom.
If I apply Redgard to the second shower, will this trap moisture between the two walls? If so, what do you recommend for the second shower?
Thanks so much!
Hi Jason,
No, it will not trap moisture. You can use redgard on the second shower as well.
Roger
I thought I read you like to use silicone in the corners. Do you have to let it dry or can you tape and mud right away. Thanks, your site is great and your humor too.
Hi Victoria,
You can tape and mud right away if you want.
Two problems:
1. How much tolerance for uneven studs can be allowed? My studs were in line, but after installing the backerboard there were some uneven spots.
2. I used the fiberglass tape that the guy at HD tossed me when I explained what I was doing. Turns out, it is not the alkaline resistant kind, just dry wall tape. I have already RedGaurded, so I am several steps away from the tape and mud steps of my joints. What now?
Hi Chet,
1. 1/8″ in 8 feet, but much can be compensated for as you set your tile. As long as it isn’t way out of whack you should be fine.
2. The board should have been taped and mudded before you redgarded. It can be done afterward, but you NEED the alkali-resistant tape for that as the thinset will eventually disintegrate the regular stuff.
Just found your site,thank you for doing it
Can RedGard on backerboard be used for shower walls with a traditional pan (pre-slope, liner, final bed)? Or do the backerboard walls in contact with the top mortar bed of the pan wick water up into the walls behind the RedGard?
Hi Tracy,
Yes, to both.
If redgard is used on the walls you need to have a gap between the backer and mud bed.
So does the Red Guard not go on the deck mud before the floor tile? shouldn’t the RG go in all the corners with fiberglass tape covering the gap you are talking about? thanx Jason
Not if you have a traditional floor. Backer will wick water, if it is placed against the mud, or into it (not leaving a gap and allowing the redgard to be painted on) then it could wick water up into the board behind your waterproofing. With that method you need to leave a 1/4″ gap between the mud and board.
And finish the gap with silicon?
Not necessary. You can if you want, but gravity will take care of the water. You just don’t want it touching the mud.
What no one seems to mention is that in cold northern climates such as Minnesota, a lot of builders put up vapor barrier on exterior walls. Just so happens my shower has two exterior walls. Therefore, these comments about skipping the vapor barrier to prevent mold growth seem inaccurate. I’m not entirely sure how mold will grow between plastic and red guard on cement board, since there is no cellulose for food. I’ve seen suggestions that cutting slits on the upper part of the vapor barrier allow moisture to travel outward and inward as the changing environment dictates. But if the entire shower is Redguarded, and the exterior cavity has a vapor barrier, there shouldn’t be enough moisture between those two cavities to allow mold growth- unless you didn’t apply the red guard all the way up the wall.
Hi Kb,
The barrier is waterproof, but not vapor proof. Vapor can still get through the plastic, get trapped and cause mold growth. If there is ANY space between the plastic and the back of the backer cellulose materials will eventually end up in there. It is accurate – I promise.
I am installing a shower from scratch. Durrock walls are in and taped. Installed a membrane before the cement floor. Want to use Red Guard for water proofing walls. Did not use poly on walls before Durrock. My question is, since I did install a rubber membrane as the pan, I assume that I should not apply the red guard on the floor as this would be two water barriers sandwitching the cement floor or is this incorrect. Basically, do I put the Red Guard on the shower floor before tiling if I already installed a rubber membrane under the floor? Thanks in advance for any input.
Hi Dave,
Correct, no redgard on the floor with a liner. You can paint it about two inches out onto the floor from the walls if you want, that won’t hurt anything.