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,
You’ve helped me with redgard & tile installation – maybe you can answer a shower door question for me. The shower pan (32″x34″) I installed has a 3/4″ lip protruding past the bottom tiles on all 3 walls. At the front of the pan the lips are about 2″ above the threshold. This will interfere with the installation of the door jams. I have not found a shower door installation video or instruction that addresses this lip vs jam. Everything I’ve seen indicates the jams stand squarely on the threshold and mounted vertically to the wall tile. It looks to me like the jams must be cut at the bottom in order to fit over these lips. But I don’t see anything saying that this is part of a normal installation. What say ye?
Hey John,
You can cut out those jambs to fit over that lip. Just hold the jambs up to the outside of the lip to get the shape and size scribed as closely as you can and cut it out with a hack saw. If you have a 10 inch tile saw and feel comfortable doing it a tile blade will cut through aluminum. Be careful! It will grab if you’re not going slowly enough. If you have any reservations about trying that – DON’T!
You don’t see much about it because there are very few of those bases that have lips sticking out like that – I think only two companies make them in that manner, but I’ve done ’em.
Roger,
Thanks so much for your help. You’ve been a real life saver (mentally) for me. I’ve been worried about this lip thing since I suddenly realized they were there – once I had all the tile installed! Also you really helped me have enough confidence to use the redgard (which I also was very concerned about). So far the installation has gone reasonably well for a dummy that has no idea what he’s doing.
Thanks again,
John
Roger,
I’ve read the whole web page. Here is what I’ve concluded. Stud, cement board, tape the seams with a fiberglass mesh tape, thinset over seams and corners, regard twice, thinset for tiles in tub surround, group, and finally seal the tiles. Sound right to you? Second, I would like to put insulation between shower and adjoining room for sound purposes. Is this a common practice? And with the insulation, I have r-13 that has plastic on both sides. is this ok to use if I staple the plastic to the studs? Thanks for the great info. Aaron
Hey Aaron,
Yup, you have the order correct. While the insulation is not necessarily common practice there’s no reason not to do it. You will want to remove, or at least cut slits into, the plastic directly behind your shower wall substrate. You don’t want the backerboard trapped between the redgard and plastic – two substances that will not allow vapor to escape. It may lead to mold or mildew and all sorts of nasty stuff.
I think I know the answer, but just want to confirm. Can you put Redguard on top of the shower pan that has a liner underneath? I guess it would be the same having two vapor barriers?
Another question, I bought a quick curb where the liner goes through the center of the curb. Because the liner does not go up and over the curb like those made with 2 X 4s, I thought about putting Redguard just on the top of the curb. Any thoughts?
Hey Charles,
Yes, you do know the answer.
No redgard on that pan as it will trap moisture in the top mud deck.
You can put redgard on top of the curb as well as really well at both ends and up the wall a bit if you aren’t using it all over the walls. You can also paint redgard on the inside of that curb if you want to – it’s not gonna hurt anything.
Roger,
I have installed redgard over hardibacker board on my shower walls. All seems to well with that. My question is concerning using tile adhesives vice mortar/water mixture. I purchased TEC Invision Ready to Use Adhesive for Tile & Stone. I have applied several rows of 4×4 ceramic tile using this and the installation appears to be fine. It is not nearly as messy and time-consuming as using thin-set. I don’t mind the extra expense since the shower is small. I cannot determine any reason to not use this adhesive and want to know if I’m setting myself up for problems later on.
Thanks,
John
I really don’t know how many more times I need to say it, or how else to say it: Pre-mixed adhesive should not be used in wet areas such as a shower.
Think about the adhesive in the bucket – it may have been setting on that shelf for one week or one year. When you opened the lid the adhesive was workable and pliable – yes? What do you think the adhesive is going to do once you place a tile over it and it cures around the outside of the tile – the places that air can get to in order for it to cure? It’s just like putting the lid back on the bucket. It will never fully cure. The combination of that and the fact that most mastics (pre-mixed adhesives) will re-emulsify when exposed to water makes it one of the last products you should use in a shower.
Not to be an ass but for some reason people don’t believe that or that a particular tile they are using makes it acceptable – it isn’t. You also have redgard on your walls which seals the transmission of vapor between the tile and substrate even more – it will NEVER fully cure. So yes, you are setting yourself up for problems later on down the road. It may be six months or six years, but it will fail.
good evening again…..
I’ve been ready to tile my shower pan for two days now but can’t get the mud deck fixed; I began laying tile and now see that my mud is bowl shaped…not straight. One website said that I could bring it up by using thin-set…so I put some down (twice as I didn’t like the first time). Do you think thin set will work(up to 3/8″ thick in some places)? If not, I can see that deck mud wouldn’t work as patching, so would I have to then come back with a second full layer of deck mud instead of just in the low spots? I’d prefer to scrape the thin set out and come back with some other type of patching filler if possible rather than work the mud…I’ve already proven that I can’t get that right and am close to calling in someone to take care of it for me. Thank you in advance for your usual good answers….regards
Hi Joe,
Patching it with deck mud requires a fairly thick layer and doesn’t sound like it would be the ideal option in your case. The thing that may work better for you is to install a layer of thinset over the entire floor with the flat side of the trowel. Do it so that the areas that are correct have just a very thin layer of skim coating and this should fill the low areas for you at the same time. If you get that fairly flat it will be much easier to get your tile installed.
Some (most) thinsets can be built up to 3/8 (although it isn’t really ideal) but the problem is that most shower floor tile is very thin so trying to fill those areas and set the tile at the same time will lead to a lot of thinset squeezing up through your grout lines. Build it up with a flat skim layer first, let it cure, then set your tile.
Here’s some feedback concerning installing redgard over hardibacker board: I went over the tape and thin set with a sanding block and then wiped the whole boards with a wet rag to get rid of the dust. Per Roger’s advise, for the first coat I diluted the redgard to 4 parts water and 1 part redgard. I used a medium size plastic glass (probably about 10 oz) for measuring. This was much more than necessary to cover my approximately 55 sq ft. The redgard dissolves very easily when stirred in. The result is a mixture the same consistency as water. This made the application a little messy so make sure the pan is covered completely. After trying a 4″ brush I switched to a roller to keep the dripping under control. I used newspaper taped to the sides and a thick piece of cardboard on the bottom. This was not good enough. I spent about a half hour cleaning up the pan when I was all done. I used warm water and dishwashing soap. The warm water seemed to be the best for clean-up. The next two coats went on with a 4″ brush without a problem. Each coat was dry in less than 2 hours. I used about 3/4 of a $42 bucket from Home Depot.
Hey John,
Thanks for the info! It’s difficult for me sometimes to describe some of these things to my readers simply because I don’t think about them. I’ve done this stuff so many times that there are a lot of things I do that control things like that. I do use a roller for the priming coat and believe I started doing that to control the mess as well. I always cover any pan or tub completely before I start any job to keep waterproofing and thinset off of them. I use moving quilts and tape plastic over them.
Thanks for letting everyone know that it’s more messy than I let on.
I think I’ve seen enough posts but wanted to verify – Mastic is NOT to be used on tub surrounds. I have put up 1/2″ Hardiboard, taped/thinset seams and applied RedGard. I have read that Mastic does not work well with RedGard and should not be used in wet applications like tubs anyway – please confirm.
Any mortars you would recommend to use with RedGard that won’t allow tiles to slide?
Hey Neil,
That’s correct, mastic is not approved, nor recommended, for wet applications such as a shower surround.
If you want a mortar that will not allow the tiles to slide you are looking for a ‘non-sag’ mortar such as Laticrete’s 4XLT. It’s great to work with but it’s a bit spendy – like $35-$40 / bag. Like mortars are comparable in price. If you start the tile from the bottom and work your way up you really don’t need the non-sag, just stack the tile on the row below it. A good modified mortar will do it.
My question is: Is it advisable to dilute the first coat of redgard?
I am about to apply redgard to hardibacker board on my shower walls. I have heard that the first coat of redgard should be diluted to 4 parts water to 1 part redgard to satisfy hardibacker’s significant thirst for water. So far I have seen nothing official (on the website or container) that agrees with this. Comments anyone?
Hey John,
It actually is not any part of the ‘official’ line from custom (redgard) because it has more to do with the specific backerboard you’re using. They won’t come out with an official statement likely due to any liability involved – I can’t say that for sure, though. With that said, diluting the redgard at 4-1 will both allow the backerboard to suck in the moisture and seal up the pores of the backer at the same time. Once it does that you have a sealed substrate which will not prematurely leech moisture from the redgard and compromise it. I always roll on a primer coat in this manner first. It also gives you better adhesion to your substrate.
I am wondering if plastic capsulated insulation is ok to use behind the durock w/your product. It appears that I will be cutting away the vapor barrier/house wrap from where the durock will be placed (only about 8ft tall by 4ft wide section) – any help you can give me to this will be greatly appreciated! I Thank You in Advance…
My wife wants me to get this right!! hahah
Hey Jay,
I, personally, don’t have a product – I’m just a contractor that uses the different products.
Not too sure why you would be cutting away the house wrap from where your durock will be – it doesn’t create any problems since you have the wall cavity itself to dissipate any moisture. The problem with using a barrier behind your redgard covered substrate is trapping the moisture in your substrate between two waterproof barriers. If your insulation has a waterproof (or vapor-proof) barrier over the face where it will contact the back of your substrate you should cut slits into it to allow moisture to dissipate into your wall cavity.
The wives always want it done right the first time. But, you know, we’re guys and they should damn well know better.
To sum up discussions: A vapor barrier on walls is required. Question is – Which is better?
To save money and time, 4-6mil plastic or roofing felt (15# ?) behind substrate good
OR
RedGard or elasomeric liquid on substrate better but it’s more expensive, requires cure time (24hr) and several coats (maybe three) + cure time. It then requires more time to finish tile job because of slower cure time (couple of days) because of mastic on liquid rubber membranes (RedGard). [Response to Roger on 30 Jan 2011, “It will grab the tile and set in a normal 24 hour period but the polymers will still need to cure before sealing it up with grout. A couple of days should be fine.”]
[Response to Dan 16 JAN 2011 you say, “The plastic barrier is a perfectly acceptable installation method, IT JUST DOESN’T LEND THE ADVANTAGES OF TOPICAL MEMBRANES IN THE FORM OF ELIMINATING WATER RETENTION.”]
So, I take it that RedGard or similar application is THE BEST METHOD and plastic or roofing felt is next best method if you don’t want to spend the time and money (which is always a bad idea in a wet area? !).
I thinking after reading much of your site, ito prevent surfaces from moving or expanding due to water getting to and into the wood and swelling (not the substrate), WHY NOT apply several coats of RedGard on the studs surface that will contact substrate, then hang cement board, tape the joints, and then apply RedGard to the substrate surface. Seems like that’s the best of all methods. No ‘double moisture barrier’ except at the studs where the potential problems generate.
Hey Brantley,
The main reason not to do that is simply that if the redgard is applied correctly onto your substrate no water will ever get to the back of the substrate. It’s simply not needed. That said, there’s no reason you can’t do it if you choose to – it won’t hurt anything at all.
The redgard or other topical membranes are advantageous because they don’t allow water to penetrate into your substrate at all. With the vapor barrier option your substrate will be saturated and will flush with every shower. Topical membranes allow your shower to fully dry out between uses. Either method works just fine when properly built. There is a bit longer cure time required over topical membranes unless you use a non-modified thinset (NOT mastic).
i had someone install and tile two showers in my home……issues have arisen…leaks down in the basement. after further contacting him, it sounds as if he did not install the rubber mat under the tile correctly.
he now tells me that he is going to come and apply redgard over the ’tile’ that is there and then pour mortor and then retile. Does this sound like it should be happening this way??
not feeling good about him screwing it up twice!!!!! lol
Hey Lee,
Redgard is not the magical fix-all he’s making it out to be. It can be used as the primary waterproofing and using it in the manner he suggests might work IF he removes the tile on the walls, runs the redgard up the walls and re-installs that tile as well. As far as the floor goes it could work but the drain would need very specific methods (divot) to work correctly otherwise your weep holes will be open beneath your waterproofing – counter-productive.
It honestly sounds to me that he’s attempting to simply put a band-aid on a shoddy installation. If he didn’t get the waterproofing correct the first time I don’t know that I would let him touch it again. The only true fix would be to remove what is currently there and build a proper shower base – short of that it is simply a temporary fix in my opinion.
I am getting 2 different answers to this question ? Do I apply vapour barrier under my durrock if i am going to use red gard as well, or do i not use the poly vapor barrier under my durrock if i use red gard on my durrock,, This will be a steam shower, Some ppl say yes i need the ploy and some ppl say i shouldn’t use it, Please advise thank you.. Bruce
Hey Bruce,
You are receiving two different answers because there are two different applications.
For a regular shower you DO NOT use a vapor barrier behind your backerboard if you are using redgard. For a steam shower you need both a vapor barrier as well as the redgard. A steam shower is a totally different construction method and an entirely different animal with substrate preparation – you need both.
Hi Roger,
Love your site. I am attempting to build a 4x6x7 steam shower with 2 interior walls and 2 glass walls. Can you please tell me the ‘layers’ from stud to tile to ensure that no moisture hits my studs? Is it 4mil poly – cement board – mesh – thinset – tile? Kerdi? Help?
Hey Trevor,
A steam shower is a very, very specialized installation – and not an easy one. Glad you’re doing your research. First of all you need insulation in all your walls and your ceiling, whether they are exterior or not, except the glass walls, obviously. This is to reduce the demand on the steam generator. You then need a vapor barrier in the form of either 4-6 mil plastic (the thicker the better) or roofing felt, which actually swells and closes up when subjected to moisture – it’s a very effective vapor barrier. Then you need your cement board installed with the proper screws. I then use a liquid topical membrane such as redgard, 9235 or hydroban, over the face of the cement board. You can use kerdi as well. What you need to be concerned with when choosing your topical membrane is the vapor permeability rating – a steam shower needs to be below 1%, the lower the better.
A steam shower is the only place you will have both a vapor barrier and a topical membrane. You also need to take into consideration a very good ventilation fan placed as close to the outside of the shower as possible. Your shower ceiling also needs to be sloped to prevent cold condensation from dripping on you – it’ll ruin your shower.
There is a .pdf from laticrete which describes all of this in great detail – it’s the best I’ve found. You can find it here: Laticrete steam shower technical design manual.
Hope that helps.
Hello!
We are installing ceramic tile (with natural stone accents) into a tub/shower area. The tile store has told me that I can use either Kerdi to waterproof the walls (which are green drywall) or Mapgegum WPS. According to my understanding of your above article, I should not be using a “liquid rubber” (as the tile store called it) to waterproof on top of drywall. Could you please let me know if it’s safe to use both procuts or if Kerdi is my only option. Thanks!
Hey Kathryn,
I’m actually not familiar with the mapgegum wps. If it is an elasomeric liquid similar to a redgard or hydroban (liquid rubber) then it likely shouldn’t be used on a gypsum-based product such as greenboard. I would check out the manufacturers website for that particular product and find out the recommendation. If you can’t find it on the site contact their customer service department – they’ll tell you whether it’ll work or not, they don’t want their product to fail. I do know that kerdi will work – I can guarantee that.
Just as an aside a lot of information people receive from tile stores is not always accurate – they’re trying to sell products. Dunno if that’s the case with your particular tile store but it is common.
Is 16×16″ ceramic tile too large to install on shower walls? If not, are there any special precautions to take during installation?
I was previously going to use a 12×12″ tile and was concerned about the size of that as well, but that tile selection (pattern/color) is no longer an option.
Hey Allen,
Nope, not too large at all. I just finished a 20 x 20 shower. The lateral shear of tile is nearly the same per square inch whether your tile is 12 x 12 or 24 x 24. The bigger tiles are a bit heavier per square inch simply because they are normally a bit thicker but not so much as to make a difference. This would only be a concern on an upside down horizontal surface such as your shower ceiling – the wall doesn’t care what size your tile is.
Roger,
Can we discuss thinset choice for setting tile on top of liquid membranes? I would think liquid membranes under tile would perform similarly to kerdi as far as slowing down modified thinset drying times, so for that reason, do you advise sticking with lightly modified thinsets like versabond or plain unmodified and avoiding heavily modified “flex” type modifieds?
Asking because I am about to do a large bathroom floor and shower pan over 3/4 ply, 3/4 osb, (20″ centers) and trying to decide between using Durock membrane or Blanke Securmat for decoupling/stress reduction, or just going with cement board or self leveling compound and a flex thinset for the floor.
Just subscribed to the newsletter – great info on this site!
Thank you,
Mike
Hey Markore,
You are correct – the liquids do slow down the total cure time of the modified thinsets because the polymers need air to cure. The portland in the basic mix, however, will cure and grab the tile and substrate while the polymers are still in the curing process. All this basically means is that it will cure – eventually – it just needs a bit more time before grouting. It will grab the tile and set in a normal 24 hour period but the polymers will still need to cure before sealing it up with grout. A couple of days should be fine.
I use versabond all the time on kerdi and liquids – I have issues with unmodifieds. Not the strength (it’s actually a stronger bond once cured) but with the lack of ‘stickiness’ – I make a damn mess with it because I can’t scoop it out of my bucket, throw a big glob on the wall, or all the other stuff I normally do with modifieds. It drives me nuts. As far as bond properties, though, unmodifieds are just fine.
With 20″ oc joists you should attempt to maximize the amount of flex your tile can handle without transferring through to the tile or grout. I would use ditra, or even ditra xl or the blanke equivalent (I’ve never used blanke) or a very, very highly modified flex thinset with cement board. I would not use the leveling compound as it has very limited flex properties and tends to crack when pressured.
Thanks for subscribing! I’m not consistent with my timelines but they’ll show up every now and then.
Day job and all…
Hi Roger,
My tile guy left yesterday and this is where we are at:
• Tub/Shower three wall alcove to be tiled
• Back wall is exterior has a window/ insulation between studs/ 3ml Poly over insulation stapled to studs/ Durock over Poly/ Durock down to top of tub flange with 1/8″gap/ Poly is behind Durock (not overlapping flange)
• Left wall has all fixtures/No Poly behind Durock
• Right wall has a niche built out of Durock/No poly behind Durock
So from reading here and other places I think things are a bit wonky. It should have been all poly or no poly with Redgard. He should have pulled the poly out over the flange, correct?
Can we just Silcone the 1/8″ gap above the flange on that back wall and leave the poly behind the Durock? Or do we need to take the Durock off and pull the poly out? Even though there is poly on that window wall should we still tape and Redgard around the window frame?
For the right and left walls we just tape/thinset the seams and then Redgard?
Would we tape/thinset the seams on the back wall as well but leave off the Redgard since there is poly behind?
Thanks,
Denise
Hey Denise,
You’re right – things are a bit wonky.
Your best bet would be to simply redgard the entire shower. Since there is a window on that back wall and the poly doesn’t overlap the flange the wall is not sealed up tight. Installing redgard to it won’t cause any problems. If that isn’t an option the only other option is to remove the backerboard and poly the entire shower overlapping the flange.
And yes, you should tape and thinset the seams before redgard.
Dear Sir:
I am currently having a steam shower installed in my home. One wall is located to the exterior which opposite is our attic space above our garage. All exterior walls were filled with urethane foam during construction. I was told by the techincal person at the local hardware store there were no issues applying redgaurd over Green Gyp brd.
three coates were applied to the entire shower walls & ceiling, next, my vinyl shower pan fastened to the coated gyp and then layer of 1/2″ Hardi board was installed to cretae a wainescoat over the coated Green brd. and siliconed at the top. The entire space will be tiled. After reading some of the comments listed, should I be concerned with Mold or integrity issue. I am hoping that we will not have to abort and start over.
Hi Bob,
If I’m understanding you correctly you’re saying that the interior of your steam shower contains greenboard as your substrate – is that correct? And if that is correct then whoever built your steam shower is not properly educated in correct steam shower construction. The urethane foam is fine and, in fact, every wall exterior or not around a steam shower requires insulation (this is to limit the amount of load required on the heat generator). A moisture barrier is then required over the wall framing, then cement backerboard, then redgard. Greenboard is not an approved substrate for any type of shower – least of all a steam shower.
While redgard does have the proper vapor permeability rating for steam showers the temperature and humidity differences on each side of the substrate will create condensation behind the redgard – in the substrate. This is why cement backerboard, as well as a moisture barrier, is required. I’m not sure who told you that there were no issues applying redgard over greenboard but it is definitely not an approved substrate for that (or any) particular waterproofing.
Unfortunately a steam shower is a very demanding and exacting construction. If not done properly it will be compromised in short order. If you’ve had a ‘professional’ build this he is absolutely liable for the proper construction. Sorry to be the bearer of bad news. If there is anything I can do to help please let me know.
I just finished reading your “Installing Redgard on Shower Walls for Tile” article and comments that followed. I noted that it is not recommended to put a plastic membrane behind shower walls that will have Redgard applied behind the tile bed due to mosture retention. I’m afraid that is exactly what I have done following my tile retailers advice to purchase and apply Redgard to the surface. Guess they didn’t realize I had already installed the plastic barrier. I’m ready to install the tile but concerned now about the mold issue. Is mold in this case a possibility or a probability? Is there anything I can do other than tear the walls out back to the studs (cringe!) and remove the plastic barrier? Can the Redgard be removed (as much as I hate too as I really like it)? Fingers crossed for some good news!
Hey Dan,
Mold in the case of a plastic barrier behind redgard is only a possibility – it may or may not grow. Unlike some construction methods this one does not ‘definitely’ lead to mold.
The only two options to completely remove this possibility would be to either take the walls off and remove the plastic or eliminate the redgard from the equation. The plastic barrier is a perfectly acceptable installation method, it just doesn’t lend the advantages of topical membranes in the form of eliminating water retention.
Hi,
I have just had someone tile my shower. I have a swanstone base and durock walls with vapor barrier behind. When finished, my installer sealed the grout and caulked with clear silicone the vertical joints in the two corners. He did not caulk at the bottom of the tiles where they meet the swanstone base. Would there be a reason he did not do this? Or do I need to caulk that?
Hi Lauren,
When you caulk the bottom of the tile installation over a pre-formed base you need to allow for weep holes so that any moisture getting to your moisture barrier will run out from behind the tile into the base. I explain those in my post about installing weep holes in tile installations. He may not have caulked it simply so as not to have the bottom caulked except for those two weep-holes, sometimes it looks funny. Swanstone bases oftentimes do not have built-in weep holes or spaces.
As long as your tile and moisture barrier are correctly installed there really is no need to caulk it. Although for cleaning purposes leaving the caulk out of it leaves small spaces for stuff to get into. I would probably install clear silicone around the bottom to keep stuff out of that space and make sure you leave empty spaces for weep holes so water can get out of that space.
Hi,
I have a question concerning using redgard. I am installing a shower in my basement and have used Durock on the walls and green drywall on the ceiling. It is a low ceiling because a bulkhead had to be built to cover heating ducts in the ceiling. My question is, should I use redgard on the drywalled ceiling (which I intend to paint) and if I do use redgard on the ceiling can I apply a suitable paint over the redgard? Thanks for any advice that you can give!
Hey Laird,
Redgard can be applied to the ceiling, then primer, then paint if you choose. The ceiling really should be backerboard as well rather than green drywall. Not that it won’t work, just that to guarantee that the ceiling substrate lasts it should be backerboard as well. Redgard, as any other liquid membrane, is not recommended for use over drywall – only backerboard.
I’m not saying it won’t last – I’m saying I don’t know if it will or not. With a lower ceiling and limited ventilation I would definitely feel more comfortable with a cement backerboard like durock up there.
in an exterior wall of a shower wall I plan to foam with closed cell insulation, which does not need a vapor barrier. If I put Durock over the closed cell foam. Can I use redgaurd over the Durock?
Hey Charles,
Yes, you can. You still have open channels, even with the closed cell foam. The areas along the wall studs will allow any minute moisture in there to dissipate and not become trapped. You just do not want to seal off the entire wall and squeeze the substrate between two air-tight materials like plastic (over the studs) and redgard. The foam will not create that problem.
Roger,
A couple shower questions for you. I’ve installed Durock on the studs with kraft paper faced insulation in the stud bays. I taped all the kraft paper seams together with Tyvek tape before hangin the Durock and wonder if that prevents me from being able to use Redgard? I’ve already applied mesh tape/modified thinset to the Durock seams/custom niches and would like to apply Redgard at least to the seams and niches if not the entire Durock surface area. Can Redgard be applied over thinset like this?
Many thanks,
John
Hey John,
That will not prevent you from using the redgard at all. What you need to be concerned with when there are two ‘moisture barriers’ like having plastic and redgard both, is the vapor permeability of the barrier. That simply means whether or not (or more specifically – how much) water vapor can penetrate the barrier. If you have plastic back there no vapor can get through it – the moisture between the two cannot dissipate. Vapor can get through the kraft paper on the face of insulation. While it is always better to physically slice open areas in the paper for this to happen, it will not create a ‘moisture sandwich’ like plastic would. You should be fine using redgard throughout.
Yes, redgard can be applied to thinset and just about any other surface you may have in your shower other than acrylic or metal. It’s actually made for cement-base products like thinset and backerboards and, you know, concrete.
Hi Roger,
I see were people attach a straight edge to a shower wall in order to start tiling on the second row. Can I screw on a straight edge over the Redgard then when I take it off fill up the screw holes with more Redgard?
Also, I just poured water over my shower pan painted with Regard to see if all the water runs to the drain. I was surprised to see it turn pink! Should I be concerned if there are a few places around the edge that holds a little water?
Thanks!
Sharon
Hi Sharon,
Yes, you can screw a straight-edge to the wall to tile – it’s called a ledger board. When you finish you can fill the holes with either more redgard or 100% silicone.
Yes, redgard turns pink again when it’s wet – the first time I saw that I freaked out too. However, after totally running it through the ringer I found that this is only a color issue – it has nothing to do with the stability or integrity of the membrane itself – it’s still completely waterproof. It is only the thinnest part of the very top layer of redgard that turns pink (I actually created a bowl out of redgard, filled it and watched the bottom and sides). I still don’t like it but it’s waterproof, the coloring still freaks me out a little bit, though.
Yes, you should be concerned with any area that hold water. If there is any standing water at all that means it will never drain. You can use some thinset to fill those areas and get them sloped just enough, let it cure, then paint some more redgard over them. Everything needs to drain, if it doesn’t now it never will.
Yer Awesome.
Will this work? If not what would work better?
I want to build a mosaic tile freestanding paper soaking sink for my print shop. About 3ft by 4 ft with a 10 inch depth. I just finished my shower floor using kurdi system and I’m feeling cocky. My plan is to build the box like a shower pan out of exterior grade plywood, and waterproof with either the Kurdi membrane or the red guard and tile. The entire box/pan will be tiled except for the bottom which will be exposed to air. My questions: 1. Is it imperative that I use cement board. Will the wood shrink and expand too much? 2. Kurdi, or red guard? It will have standing water in it for long periods of time, but no steam as it will only be plumbed for
cold water. It seems like it would be a no brainer to me, which makes me suspicious that I’m totally misguided. Your guidance therefore would be much appreciated.
Hi Lisa – Yer awesome!
It’ll work provided you use cement board.
The problem is not with the waterproofing ability of kerdi over plywood – it will waterproof it just fine. So will redgard – either one would work just fine. The problem would be in the expansion and contraction of the plywood over time. This is normal stuff – and may be fine for a couple of years. You simply don’t know how much it will move over time – it isn’t consistent – and any movement under tile is bad. If you continue to move your tile substrate up and down (the expansion of the plywood) over time, no matter how small that movement is, the tile will eventually become loose.
If you want it to last you should use backerboard for your substrate.
Redgard is an approved waterproofing method for waterproofing below line (under water – the bottom of a sink or shower) but you need to use fabric reinforcement at all changes of plane and at the drain. These are simply the areas most prone to movement and the fabric reinforcement keeps the membrane intact. It is similar to landscaping fabric and can be purchased wherever you get redgard. If it were me – I’d use the kerdi.