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 contractor that skimmcoated a wood floor to cover the heating lines for in-floor heating with thinset, to level it and let dry , will it be ok to tile onto that or ditra onto that or will it not bond correctly? thinset to dry thinset? Please? thank you
Hey Bruce,
That’s just fine. I do the same except I float out those wires and install the kerdi (or ditra) all at once. But letting it cure and going over it won’t be a problem at all, I’ve done that as well.
Roger,
In your opinion, what is the best type of cement mix to use for the top layer of the shower floor, before tiling, and what is the ratio of water used in mixing?
Hey Mike,
Regular portland and sharp sand at a 1:5 ratio. The amount of water will vary due to several things, the amount of moisture in the sand, humidity, temperature, etc. I can only say definitely just enough to make it damp.
Hi, quick question, when installing a heating mat or infloor heating lines for heated tiled floor,this will be on a plywood subfloor, does one install the heating mat under the ditra or above? Thank you,, GREAT !! site.
Hi, quick answer: Under the ditra.
My new shower is 3’ x 3’ on wood subfloor, with two stud walls and one brick exterior wall with ¾” furring strips to the bricks. All walls have polystyrene insulation board cut to fit snuggly into the gaps. Hung plastic on the studs and furring strips, then mounted the CBB with screws. Should I apply Redgard to the screw heads? I’m concerned that where I punctured the membrane with the mounting screws, I could get moisture penetration to the wood.
Hey Bob,
Water running down the plastic will run around those screw heads. As you screw them in it creates a ‘pucker’ in the plastic, that coupled with the substrate being firmly against the plastic creates a dam that water will run around rather than into. No need for redgard – wouldn’t do any good from the face of the board anyway. Water doesn’t run sideways unless it is into a porous substance like wood. A screw in cement backer is not a porous substance.
Roger
Thanks for all your great advise. Just finishing up the shower. I want to instal trim tile over the ceramic wall tiles in certain areas (outside corner, around the niche etc.) The wall tiles are 12×12 the trim is 1/2″ x 12. I was wondering what is the best method to attach the trim pieces to the wall tiles. I was considering an epoxy glue or thinset. Have no idea what expoxy to use or if there is a better method. Thanks again you have helped me from making a lot of mistakes or causing future problems.
Hey Keith,
There are several tile-specific epoxies but nearly any epoxy will work for that. I like the kind that starts as a gel – much easier to control and less messy.
Roger,
In constructing my shower curb, can I use hardibacker on the outside surface, and mortar the top and inside surface?
Hey Mike,
Yes, no problem with that at all.
Let me see if this is correct? Tiling a shower with 2 outside walls, these 2 walls will need to have slits in the poly correct? , Than i can cement board, thinset the joints with mesh tapes, and then red gard, , and than tile, Will I be fine with this process ?
Yup, you got it. Whaddya need me for?
Roger,
I am reading that hardibacker contains cellulose material (10%) and that wonderboard or of course kerdi are better for avoiding mold. This person was also suggesting painting wood behind the cement board with paint then reguard on top of using redguard as a barrier on cement board surface under tile. I’m not sure why paint the studs first unless the reguard absorbs too easily. This is most likely overkill but wanted to get your thoughts especially on the idea or fact that hardibacker contains cellulose, which for me would definitely require reguard as the vapor barrier applied on the reguard behind the tile instead of the plastic barrier behind the cement board.
Thank you,
Robin
Hey Robin,
Hardiebacker contains about 10% cellulose fiber which while dormant (not thrown into the air in the form of dust particles) is a non-issue. However, redgard would definitely be your best bet to contain any off-gassing, which can happen with new boards. There is absolutely no reason at all to paint the studs – that’s a new one on me. If that were required the redgard would be a fairly ineffective waterproofing and vapor barrier. And it isn’t – it’s a very good one.
with redgard What I am not clear about is the silicon just weep holes at the bottom row so for all other rows above that I have to use silicone I can not use pretty colored grout?
Weep holes are only installed in the silicone line between the tile and tub. All the tile gets grout, the plane change between the tile and tub or base gets silicone with weep holes. I just uploaded two photos at the end of this post: Weep holes in shower tile that show what the finished weep holes and silicone bead look like.
When you redgard your walls you want to silicone between the backerboard and the tub completely – no weep holes. The only place that gets silicone is that transition between the tile and tub, everything else gets pretty grout.
Roger
After installing Redguard do you have to worry about compromising the waterproffing when you use a notched trowel to apply the thinset?
Thanks for all your great advise.
Hey Keith,
Not really. Provided you are normally troweling it and not going at the wall like an axe murderer it will be fine.
When installed to the correct thickness it is fairly tough, more than enough to handle normal troweling. If you use it for a shower floor or something and are going to be walking on it you should cover it – it doesn’t handle repeated foot traffic (abrasion) before being tiled over.
roger,
I have a few gaps between my backerboard, where less than perfect cuts were made. Should I silicon fill before taping with thinset, or is there something else to use as a filler in the seams? I will redgard after seams are taped.
Hey Mike,
Yup, silicone those gaps to keep thinset out of them as you are taping them.
ok want to be sure i do this right
1 hardy to stude to 1/16th gap then from tub lip below caulk leave weep hole at inside corners,( then ? Caulk the corners ? )then
2. thin set all seams ( ?including corners?) then tape over that then thin set and feather all seams let all set
till dry
3. then redgaurd corners and all seams at least 2 caots with curring between coats then go to to town tilling
Nope.
1. Hardi to studs to 1/16″gap, silicone all the way around that gap, no weep holes. Silicone the corners as well.
2. Thinset and tape all seams – corners as well but make sure your thinset does not get in that gap, hence the silicone there.
3. Redgard everything all the way down to the tub, over the silicone as well. It won’t stick very well, but it will ensure a full seal on each side of it.
4. Install tile leaving a 1/16″ gap at all changes of plane as well as between the tile and tub.
5. Silicone all those gaps leaving weep holes in the silicone bead between the tile and tub.
so after tile is all done I am to use silicon instead of grout and leave weep holes between bottom tiles and tub.I am sorry as you probably can see I am visual learner
thaks so much for all your patients
carol dawson
Yes, that’s correct. You can see where and how to leave weep holes here: http://floorelf.com/location-of-weep-holes-in-tile-installations
Roger,
with red gaurd still need weep holes right?
thanks
Carol dawson
Hi Carol,
Between the tile and base yes, the redgard must be a continuous layer.
Roger,
Two questions regarding RedGard and the pan membrane. First, I know you said not both, but when I install the backerboard, at the bottom where the board goes over the membrane, there will be 6-8 inches of overlap of membrane and redgard. Is this OK? I’m assuming it is, but want to make sure.
Second, can I construct my curb with backerboard vs. mortar? I know there would be a few unauthorized screw connections, but was hoping I could redgard over them to seal, although that would give me both redgard and membrane on the curb.
Thanks.
MP
Hey Mike,
Yes, the redgard where the board overlaps is fine. No, you cannot make the curb with backer. You CAN, but if you screw through that membrane you’ve negated your entire waterproofing aspect. The curb is the most commonly misconstructed aspect of a shower, and normally the first place that will leak. It must be constructed properly and it must not have screws through the membrane. Redgard won’t fix it.
Wonderful site for info. Full reno. of small bathroom. Have put down Durock on floor but noticed that there’s a 1/4 to maybe a little more unlevelness in floor from one side to the other (approx. 4 feet). I was told that I could use a product called “Feather Edge” to level out floor. Then I could apply redgard once that has dried. I can then tile with level floor. I’m worried about the levelness of the floor (even small amounts) because there will be tile on three of the walls as well. Need everything to tie together since unable to alter grout lines on subway tile (butting them together). Water wall 1/2 way up wall on one wall, which flows into open shower with the glass doors. Using subway tiles on walls, and 1 inch hexagon 12 inch field on floor. Is this all correct???
Hi Cindy,
First of all, I really don’t think so but I HAVE to mention it anyway – I want to make sure you are NOT talking about your shower floor, which is supposed to be sloped. I know it sounds ridiculous, but people do some ridiculous things.
Yes, you can use featheredge and redgard to level your floor and set tile over it, no problem at all. Everything else sounds fine (as long as you are talking about butting small subway tiles with nubs on them).
1. no, not shower floor. Used Kerdi Shower System with pre-sloped pan & curb. Was a bit tedious as far as making sure all air bubbles are out but loved otherwise. Water test for pan (48 hours and working toward 72) is perfect so far.
2. yes, subway tiles with nubs.
3. Question… What do you do about the space between the floor (durock) and water wall (durock)? And, space between floor (durock) and other walls (mold resistant gypsum)? About 1/4 to 1/2 inch. Silicone caulk?
Thanks so much!
1/16″ space and silicone between the durock wall and floor and 1/8″ between durock wall and gypsum wall, fill gap with thinset, cover with alkali-resistant mesh tape, and feather out with more thinset – just like taping and mudding drywall. Unless you’re using kerdi over that space, in which case just fill it with thinset then kerdi as usual.
Roger,
I have 2 recessed shelves with 1/4″ plywood backing. Can I Redgard and tile, or do I have to put cement backerboard against the plywood?
Hey Mike,
Although not ideal you can redgard those and tile them. Keep in mind that wood moves – a lot. Even with a couple of layers of redgard over them there is still a good chance that the normal seasonal movements caused by the changing humidity inside the wall cavity will cause the wood to expand and contract. I would be better to install a layer of even 1/4″ backer over it first, even better to remove the plywood altogether and use backer installed directly to the framing.
Thanks Roger,
I’ll probably put a 1/4″ pc over the plywood, as the plywood is liquid nailed to the drywall, and trying to get it off will tear the drywall, unless you have another suggestion.
Thanks for all your help
Do I have to waterproof the cement backerboard in my tub/shower installation, or can I just tile right over it?
Hi, umm, you. I refuse to call you king, I’m not british.
Yes, you must either have a moisture barrier behind it (plastic or roofing felt) or a topical membrane such as redgard or kerdi. Cement backerboard is not waterproof, it simply doesn’t swell or deform when wet. It will still soak up water and allow it to get to your wall framing.
Roger,
Should I Silicon caulk the backerboard seams before taping, and applying RedGard?
Hi Mike,
Nope, you should tape and mud the backer seams with thinset, let that cure, then apply your redgard. If the seam is in a corner then yes – fill the seam with silicone first to keep thinset out of it.
I have showers in a metal stud on concrete slab home with “denzel board” (sp?) walls. The wallboard is a sheetrock type product with a rubber side to which we intend to adhere tile. Before anyone could think, the mud crew paper taped, metal corner beaded and finished with joint compound. Now, the tile man wants us to rip out the paper tape, corner bead and compound. He believes the tile in the water areas will come loose in a few years if we don’t. What is the best solution? Should I wet soak the joint compound and unscrew the corner bead and do it over with fiberglass tape and thinset or is there a product anyone has used to a good end sealing a wet area finished the way I describe?
Will I not create a second membrane by painting a product like RedGuard over a rubber type surface, thus increasing the potential for mold?
Thank you for any information. Pete
Hey Pete,
The drywall compound needs to go – your contractor is correct. Eventually water is going to compromise it and, in turn, the bond of the tile. It should be taped and mudded with fiberglass tape and thinset. If you choose to use redgard, while it is a second membrane, it would be fine. A membrane directly on another membrane doesn’t create problems provided they adhere just fine and play well together.
Thank you for your kind reply Roger. Just to make sure I have it correctly, 1.) remove the mud and tape, AND CORNER BEAD?, OR, 2.) go over the mud , tape and corner bead with RedGuard? If I remove the corner bead, there will then be remodeling issues. The corner bead was put in to stay. Pete
Ideally yes, remove the corner bead and replace it with a plastic one which will not be affected by water. Since there will be remodeling issues if you do that you can just go over it with mesh tape and thinset, then cover it with redgard enough to ensure that water will never touch the thinset over the corner bead.
Roger,
I’m in the early stages of replacing a fiberglass insert with a fully tiled shower. I’m ready to begin the shower pan installation. Just hearing about RedGard, here is what I plan to do. Your feedback is appreciated. I’m on a slab, and am going to put my first sloped mortar application, followed by a rubber, waterproof membrane, followed by my finish sloped mortar surface. I was going to then, apply RedGard before tiling. How clost to the drain do I apply RedGard? I’m using the 3 pc drain with weep holes.
On the walls, with my backerboard attached directly to the studs, use RedGard before tiling. The curb will be mortared on top of rubber membrane, with RedGard applied lastly before tiling. When taping and using RedGard on the seams, is this also done on the base, where the backerboard meets the shower pan?
Thanks,
MikeP, West Lafayette, IN
Hi Mike,
With your shower floor you want to use either the rubber membrane or the redgard, one or the other – never both. If you use the redgard you’ll need to either use a topical drain (like a kerdi drain) or utilize the ‘divot’ method. You can use the rubber membrane on your floor and utilize the redgard on the walls as you’ve stated – no problem with that at all. The backerboards should be taped and mudded with thinset, and redgarded with tape in the changes of plane (corners, where walls meet the floor, etc.). At the floor you want to paint the redgard only about two inches onto it out from the wall.
Thanks Roger. So I can tape and Redgard at the bottom, where the walls meet the floor? Doing that, I’m assuming no space is needed.
Thanks for all your help.
Hey Mike,
No tape required, in fact you shouldn’t have it there. You need to leave the backer off of the mud deck about 1/8″ and silicone between the board and the mud deck. Backerboards can actually wick moisture from the mud deck, silicone prevents that. Just leave the gap, silicone it and paint the redgard right over it.
About halfway down the page starting at post #44. Divot Method
Hi Roger,
I installed 15# roofing paper on my studs for a vapor barrier, then put Hardibacker board over that, and have taped and mudded (using tile cement) the 1/8 gap b/t same-plane seams, and siliconed the corners. I had planned to paint the Mapelastic Aqua defense on the Hardiback boards. Now I see the concern about mold forming in the concrete board of there is paper behind the Hardibacker board
I had figured that mold would not form because if any water did penetrate the Mapelastic barrier, it would simply run down the 15# paper and to the pan. Am I wrong?
Am I better off not using Mapelastic and just tiling over my Hardiback board with no aqua defense on it? I would rather not rip out everything I’ve done in order to tear out the 15# paper so that I can reinstall the Hardibaker bpard and then use the Mapelastic.
In the alternative, could I paint Mapelastic on parts of the walls (such as the seams of the boards)?
Thanks very much!!!
To follow up — I wonder if there will be “breathing room” behind the board because the roofing paper is overlapped like shingles — not a solid sheet from top to bottom??
Hi Jamie,
With roofing felt back there you should be fine using the mapei waterproofing.
Roger, your comment to Jamie was helpful to me–I will now use Redgard on my handiebacker walls with roofing felt behind. But, I have been advised to use use tile mastic over my mold-resistant fiberglass tape on my seams, because it will sand smooth, and thinset won’t. What do you think?
If you don’t have the hardibacker up yet don’t bother with the roofing felt – it is not needed. DO NOT use mastic over your seams. I don’t know who told you that but if you try to sand mastic you’re gonna end up with a gummy mess. You CAN sand thinset. I think whoever told you that likely has no experience with either.
Good site. Question about Regard on a shower I am building. 3 walls are Durock and the ceiling is drywall. The ceiling and one wall, an outside wall, have plastic behind them. 2 walls have nothing behind them. Should I use Redgard? Should I put Redgard on the ceiling?
thanks in advance
Hey Gary,
It would be best to cut slits in the plastic behind those two areas so vapor between the two barriers has a way to dissipate. If you are tiling the ceiling then yes, use redgard on it. If that’s the case the drywall there should be replaced with durock as well.
Hey Roger,
Another question, sorry to be a bother. What would you recommend, RedGuard or Kerdi? I already have Redguard, and will be using Hardi Backer for my shower walls, but was seriously considering going with Kerdi instead. What’s your opinion, should I just stick with the Redguard, (man, that pun was almost as bad as yours ;-), or go with the Kerdi? Thanks in advance for your opinion / advice.
I always prefer kerdi over redgard. It is more difficult to work with, has a bigger learning curve and would likely take longer to prepare for a beginner, but it is a system I prefer. 90% of my showers are built with kerdi and/or kerdi-board.
Hey Roger – Happy New Year! I think I know the answer to this but I wanted to get your opinion. Used Regard (4 coats) for the walls of my shower and used a Noble products membrane for the floor. When I applied Redgard on the walls, I also did two or three inches of the floor (I stopped the Hardie Backer about 1/4″ off the floor and applied a hell of a lot of silicone in between, per your suggestion). Anyhow, I tiled the walls today and as happens, I dropped a few clumps of morter (Laticrete 253Gold) onto the floor. At the end of the day as I was cleaning up I scraped the clumps off the floor and the Regard pulled off the floor instead of adhering to the floor. At this point I simply took a knife and scored the Redgard along the wall tile line and any Regrard that wanted to come up had a break point. Some came up. Some stuck like glue…so to speak.
I assume that because the floor is sandy and dirty, the Redgard didn’t adhere. I was wondering if you ever ran across this? The walls seem to be fine…the tile hasn’t fallen off yet!
Thanks again for all the help.
Regards,
Dale
I’ve seen it, it’s normally just from not getting it into the pores of the substrate really, really well with the first coat. As long as any unadhered areas were not larger than about four square inches or so it will be fine, it’s still a solid continuous membrane (before you cut it out
). I assume you mean the noble traditional liner (under the mudbed) and not the Noble topical sheet membrane. Your liner should run up behind the walls at least three inches above your curb so your waterproofing overlaps just fine, it won’t be a problem.
i have one question, for now. when using redguard for topical membrane, do you do the shower pan then backer board or backer board then shower pan? i appreciate your time and information.
Hi Michael,
I do the backer then the shower pan. That way I can draw all my reference lines on the walls as I’m fabricating the pan. You can do it either way, though. If you do the pan first make sure to silicone any gaps between it and the backers to allow a continuous plane for your redgard.