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.
Mold sandwiches aren’t on the menu, so I want to make sure I don’t order one. My new shower (plumbing wall) backs up to my new tub (plumbing wall). I was planning on using RedGard to waterproof it all (no traditional vapor barrier). But…. will the two redgarded walls that share studs create that damn diseased sandwich. If so, what are my options? This my sound dumb, but can I open up the ceiling on each side of some of the studs to allow vapor/moisture to release?
Hey Denise,
Nope, no problem at all. Moisture can dissipate from the wood (if any ever gets back there) into the wall cavity and will eventually fully evaporate. It’s when you have a solid object sandwiched between two barriers that a problem may develop.
Roger,
Sanded or unsanded grout? I have 1/8″ grout lines, although my corners, which were somewhat challenging, are about 3/16″. I’ve been told, although messier to work with, to use unsanded for the shower, due to the roughness of sanded, and the probability of collescing soap scum over time. What would you use?
Thanks,
MP
Hey Mike,
I would use sanded. If you need to be worried about the ‘roughness’ of the grout coalescing scum and such there are bigger problems with the cleanliness of the shower than a 1/8″ grout line.
The last time I used unsanded grout in a shower was 1994 – seriously. I use sanded all the time.
Good article. You might want to add that the folks at Redgard suggest that if you apply with a roller, you apply the first coat horizontally, and the second vertically (i.e., 90 degrees different) to ensure proper coverage.
Thanks Davis, I’ve changed that to the proper recommendation. I appreciate you bringing that to my attention.
I am installing a wetroom on a second floor, above a family room. I was considering painting the backerboard on the floor and walls and for double protection install the PVC sheet membrane on top of the mortar providing my pitch to the drain. I would then put another layer of mortar on top of the PVC membrane and lay the tile. Would I be providing an opportunity for mold/mildew with the double protection?? Any advice owuld be appreciated!
Hey James,
Either one of those products, installed properly, will be completely waterproof. Using both will create a problem where one does not exist. If you choose the liner method you said you would place a layer of mortar over it – I hope you mean deck mud and not thinset mortar. It could create a mold sandwich, it just depends on how much moisture it sees as well as many more factors. If you have the redgard installed (I’m assuming here that by ‘painting the backerboard’ you mean with a liquid membrane?) correctly there is absolutely no need for a double barrier.
THANKS Roger! I would have mad a mistake if I had not found you and asked! By “painting” I was referring to “RedGard” and by “mortar”, I meant “deck mud”. I’ll decide which one to use and go for it; RedGard seems much easiier to use. Thanks again!
Just makin’ sure. ;). The redgard is a much easier product and method to work with for what you have there – I would go that route.
Greetings Floor Elf and props to all the great info you share with the DIY community, you rock.
of “just put it in and it will be fine 
” is not a very good confidence booster for me. Thanks again.
Now here is my new delima. I am redoing a bathroom in a basement – the floors are well cured flaw/crack free concrete, 60+ years old, and the walls are 8″ cinderblock with a plaster like coating over them in a thickness of about an inch and painted. Two of the walls are exterior walls and 2 are interior.
I know what to do with the shower floor and walls now, thanks for that info, but now my wife wants to do all the walls and the floor in the rest of the bathroom. The floor is solid and in great condition so I figure I can just use a flexbond type of thin set mortar to bond the tiles right to the floor (cant really justify the cost of DITRA in my head but i dont want to have to redo this in 5 years) but the walls are my bigger concern as i dont need a sign on the bathroom door stating “Danger Falling Tile”.
Do i need to put up cement backerboard over the walls/floors? Redguard them? Or since the plaster material is similar to concrete can i just use a similar type of flexibond thin set on the walls and back butter the tiles as well?
I am pretty sure I will be using a rectified impervious porcelain tile with a PEI of 3-5 for everything in this room. The advice of someone who just wants it done already
Hey Kris,
As long as your plaster on the walls is good and solid you can use flexbond and just set it all right to the concrete as well as the existing walls without danger of falling tiles. Really.
AWESOME!!! I was so hoping you were going to say that and yes it is still good and solid.
Hi There,
Usually we are folks who do everything by the books, but in this case we were taking advice from a friend
And have gotten ourselves into a pickle. Our current setup is vapour barrier behind green board as our whole bathroom was covered with slat boards with 2 outside wAlls. It has already been puttied at the cieling and I’ve read a lot on you site here that what we have done is wrong and bad! There are alot of hours put in at this point. We are hoping to tile and were planning on using red guard first but now I’m not to sure what to do. What will happen if we continue? What do you suggest?
Hey Dawn,
The simple answer is that the greenboard needs to go. It is supposed to be ‘mold and water resistant’ – it is neither. It is also not a proper substrate for redgard. If you place redgard over the front of it with a barrier behind it you will trap moisture in between the two with no way to dissipate – a PERFECT breeding ground for mold, especially with greenboard between the two.
The area inside the shower needs to have the greenboard removed and replaced with cement backerboard. If you want a vapor barrier no need for redgard, if you want redgard forego the vapor barrier.
Didn’t you post that drywall was ok but not ideal? My husband is wondering if we could slice through the drywall with a saws all to slice the vapor barrier in order to provide the moisture a place to escape? I know the best bet would be to redo everything, just wondering if there is a way around that.
The only time drywall is ok is behind kerdi – that’s it. Drywall is not an approved substrate for redgard, barrier or not. Whether or not you allow moisture to dissipate in some manner you are still applying the product over a substrate for which it is not approved. It may fail. It may not. I simply don’t know. I do know that if a manufacturer specifically states that their product is not approved for use over a particular substrate there is a good reason for it. I also know that if both the International building code and the tile industry standards state that greenboard is not approved for use in a wet area there is also a good reason for that.
You can, of course, do whatever you wish to do. It may or may not fail. I cannot guarantee failure, I can only give you methods which guarantee success. What you have there is not one. I realize the stage at which your bathroom is would require a considerable amount of work to remove the greenboard and replace it with proper materials – I get that. But if it does fail it will not only cost more work but much more time and more money that you’ve already spent. The only way around that is to take a chance that it won’t fail. Sorry.
I know the benefits of ditra, but am trying to understand RedGard as a crack prevention.
Can , you can use RedGard directly over interior plywood and then put down the tile. (eg. a bathroom floor ? Will this help prevent cracks as the ditra , and also give the thinset a good surface when installing the tile. Am I seeing this correctly?
Thanks for any and all help.
Hey Bruce,
Custom building products (the manufacturer of redgard) states that it can be used over exterior grade plywood in an interior non-wet application – a bathroom floor. So yes, technically it can. I don’t agree with that. Redgard gives you crack isolation properties for in-plane movement – I don’t see how it would compensate for normal expansion and contraction in the plywood over the long-term. But, yeah, custom says you can do that. I say you shouldn’t, but I’m just a tile guy.
Hey There,
Were renovating our downstairs bathroom. For the shower we have decided to tile the walls and floor. I’ve found your site vary helpful and believe we may use the Redgard as you mention. Our walls will be cement backer board which I will line with the Redgard as you suggest. My question is this, the current floor is concrete. Am I able to use proper mortar or more concrete to make the proper “Slope” without having to install a “Schluter” type system? Sounds crazy but I cannot find an answer to this question. Any help would be greatly appreciated!
Hey G,
You can build the floor with a proper deck mud mix. If you want to use the redgard to waterproof your floor as well rather than using a liner between two slopes like this: building a shower floor then you’ll need to utilize a topical drain or the ‘divot’ method for the drain.
We were planning to do a redgard type tub surround installation. The drywall subcontractor just put joint compound on all the durock joints (and I think also used plain old drywall fiberglass tape, not the durock stuff). Also the durock was installed with drywall screws. Will the redgard sufficiently make up for all these flaws (thereby waterproofing the joint compound and screws), or do I need to have it be taken down and reinstalled with durock screws, durock tape and thinset on the joints.
Hey Andy,
While not ideal, as long as the heads of the drywall screws :cencored: aren’t sticking out then going over everything with redgard will be fine.
Thanks. As many have said before, site is an invaluable resource.
Roger,
Just wanted to confirm your answer to Carol Dawson. One of my shower walls is an outside wall and there is already plastic up over the insulation. If I plan on using redguard on my backerboards, should I remove this plastic and install the backerboard right over the insulation? Thanks.
Hi Andy,
Didja think I was drunk when I answered her?
You need to either remove or cut slits into the barrier on the outside wall and redgard everything.
Hi Roger,
I am currently doing my bathroom renovation because there were molds on the drywall (It is all taken off). I am going to use the plastic vapour barrier to cover the insulation and studs, and then I will put the cement board on top of it and a thin-set mortar to install the tiles. Is it good enough? Or should I remove the plastic vapour cover and use the redgard to protect the cement board? Moreover, what type of mud/compound should I use to cover the cement board joint? Last question, I have a greenboard (water resistance gypsum) on top of my shower, what should I do to make sure it is fully protected? Should I use redgard -> primer -> paint? Thanks a lot!!!
Kevin
Hey Kevin,
Either method will work just fine. The redgard is a more efficient system simply because the backerboard will never get wet. But both of them are completely waterproof. To tape and mud the seams just use thinset that you will use for the tile. Ideally the greenboard should be removed and replaced with backerboard. I don’t think primer will stick to the redgard – but it might. You can try it, if it sticks it’ll work fine.
Rodger,
I applied Redguard to cermet boards on the shower walls. The shower has a pre-slope mud bed, liner, and mud bed as you have described throughout your website. I wanted to know your thoughts above using the leftover Redguard on the surface of the shower floor before tiling. I understand the concept of water draining through the mud bed and routed via the liner to the weep holes in the drain but was just wondering about it after inhaling the fumes from the Redguard.
Hey Paul,
If you have the liner between the two mud decks you don’t want to coat the surface with redgard – it will create a double barrier and may lead to mold.
Stop freebasing redgard!
If I seal grout and use regard will it create a double vapor barrier creating moisture problems?
I was thinking about painting ceiling (hardiboard) with redgard applied. Bad idea?
Hey David,
No, it will not create a double vapor barrier because sealer is not a waterproofer – it allows for vapor dissipation.
It’ll be fine if you can get the paint to stick to the redgard. Which it won’t. So it probably won’t work.
Roger,
I decided to tile my walls first, all but the bottom row. If I decide to do bottom row before doing the floor, what size gap should I leave between the bottom and the shower pan? Do I grout this or caulk, or both? I thought doing the floor last would cover any uneven wall tiles.
MP
Hey Mike,
As I said in your previous question, I usually leave a 1/16″ gap no matter which way I do it. Any change of plane – that one included, needs to be silicones rather than grouted. Just out of pure curiosity – why would you have uneven wall tiles?
Good Evening…
I’m ready to tile my bathroom floor and shower walls, so i wanted to confirm my current setup before installing the tiles. For bathroom floors (basement), i layed down a platoon membrane and 1′ inch plywood as my subfloor on top of the concrete (Concrete -> Platoon Membrane -> 1′ plywood). I also TAP CON every 2 feet spacing of the floor to ensure no movement. I’m going to be adding 2 coats of RedGard membrane tomorrow. As for the Shower walls, I currently have vapor barrier behind the WonderBoard (Cement Board). By the way, the bathroom walls including the shower are insulated with R14. I wanted to confirm this setup and get advice on what type of thinset i should use for the floor (on top of Redgard) and shower walls.
Thx
Hey Mac,
Everything sounds fine. Make absolutely certain that you leave a 1/8″ gap between sheets of plywood as well as around the perimeter of the room. You want a good modified thinset such as Laticrete 253 Gold or Mapei Ultraflex II for tile over the redgard on that particular floor.
Thanks for the quick reply, Roger. what do you recommend for the shower walls?
Nevermind, the Laticrete 253 should be fine on the cement board.
Yup, 253 works for mostly any substrate.
Roger, My basement shower is all cinder block that’s been painted and has started to peel. I have spent a couple of days prepping for new paint and then saw your thread on Redgard and Laticrete products. Is this something that can be applied over the old paint after roughing up with sandpaper and/or wire wheel? If so, can it be used by itself or does it have to have tile applied? I can live with the red or olive green color of the above products. Thanks, Bill M
Hey Bill,
Yes, it can be applied to the roughed up paint. It can not, however, be used by itself.It is not made to be a ‘wear layer’ which means it does not stand up to abrasion long-term in any form. It’s meant to be covered up. And unless you have tile installed over it there is no positive pressure on the product.
What I mean by that is the forces acting on a given layer in a substrate lamination are known as positive and negative pressures. The positive being the force applied to the layer when that layer is over or against another solid layer. The negative pressure being the opposite. If you have vapor dispersion or pressure coming from the cinder blocks (what made your paint peel) that is negative pressure acting on the layer of paint. The redgard or hydroban would be the same. You would still have negative pressure acting on the layer over the wall from the backside. If tile were installed over it this becomes a positive pressure scenario and turns the layer into a neutral pressure lamination – it will last. Without something over it the product is likely to do the same thing as your paint.
In scenarios such as you have there it is normally the best idea to place furring strips onto the wall and installing drywall to them. This gives the vapor dispersion from the wall a cavity into which it can dissipate. Then paint right over the drywall. The small cavity created by the furring strips becomes the buffer for the pressure.
Physics lesson over.
EDIT: I just reread your question – this is inside a shower??? Paint will not last inside the shower. Neither will the other products – water causes abrasion on the surface and will eventually wear away the product. It needs to be covered with something. AND your shower needs to be waterproofed with something, even if it’s a fiberglass surround. You don’t live in Florida, do you?
Man, I answered that one the hard way.
So I ripped out the drywall as you advised and then hung hardibacker. I am going to go over with the aquadefense or redgard ( do you perfer one or the other). Question being. I used caulk in the corners already, do I tape and mortar over that or do I just redgard/aquadefense?
Another question the wall where the showerhead/knobs it comes out the 36″ and then is a corner to a 4″ wall. On that corner what should I use to transition. The metal corner piece one uses in drywall or should I tape/mortar to seal the end?
Thanks again for all your help. I would of never attempted this without your website. It truely is the best.
Hey Misty,
You can just redgard over that silicone in the corner. It won’t stick very well, but the parts it doesn’t stick to are already sealed by the silicone.
I normally use a plastic corner bead on any corners around a shower. If it’s more than six inches away from the shower, though, you can just use the metal bead on the corner.
OK – so I have the Redgard – now, we are using it on the bathroom floor, first we have
plywood, then 1/4 ” backerboard, then “Warm your floor” heat wires on webbing,
THEN we would like to use the LevelBest self floor leveler , and then use the REdGard,
and then mastic and tile. Does that sound like a good order to you ???????
Thanks for your help, Vickie
Hey Vickie,
Yup, sounds good, as long as by ‘mastic’ you mean ‘powdered thinset sold in a bag that you mix with water’.
Hi Roger,
I have almost have walls ready I have 1/2′ hardy tub shower area and 4′ high around rest of bathroom I am ussing redguard .on outside wall plumbing is all way cross if I use all hardy on oust side wall (also has window small) i am thinking I want to tile that whole wall insolation at tub i pulled vaper barrior off because redgaurd should i do that on that whole wall and red gaurd it ?then next question tile floor will meet 3/4″x 5″hand scraped prefinished hardwood what if anything should do to make it right highttile to wood and and waht to marry the two at thresh hole at door way?
Thanks so much,
Carol dawson
Hi Carol,
Yes, you should remove, or at least cut slits into, the barrier on the outside wall and redgard everything.
You’ll need to build up the substrate / thinset to the proper height to be level with your wood. Schluter makes several transition strips that can make that transition. You can also just leave a gap there and silicone it – DO NOT grout it. It’ll crack.
thank you for your quick reply you have been wonderfull
Carol dawson
Can I use the redgard directly on hardiboard? I have an open shower and I may get a little
water on the bathroom floor, I thought I might apply redgard to the hardiboard on floor before I tile….??
Hey Vic,
Yup, no problem with that at all.
Hey Roger,
Getting ready to install the floor. Should I complete it, with grouting, before starting the walls?
You can if you want to. It really doesn’t make any difference at all. If you do the floor first and complete it that does give you a more solid surface to work over as you are doing the walls.
Would it be a problem to use redguard on the studs facing the tub enclosure as an added barrier against any leakage beyond the membrane? I know this harkens to the “moisture sandwich” effect, but shouldn’t the moisture should be able to evaporate through wicking action in the 16 or so inches between the studs?
Hi Matthew,
If you need an ‘added’ barrier, then your initial barrier isn’t doing the job, eh? You can do that if you want – it won’t hurt anything, but no real need to.
The problem with using the redgard rather than a barrier (I know that isn’t what you asked, just putting it here for others that may think of doing it) is that yes, the moisture can evaporate into the wall cavity, but it will also condensate there on the sides of the studs.
Roger,
hardibacker installed, but all screws are not exactly flush, and can’t get them to screw any farther. Will this affect the tiling process? I’m going to Redguard before tiling.
Thanks,
MP
Roger.
Amendment to previous post. Hardibacker installed, but some of the hardibacker screws didn’t countersink. When placing tile over them, they tetter a bit, from the higher than board screwhead. Will the 2 coats of redguard and the thinset compensate for this at all, or do I need to go back and countersink all the holes? Could it be that my drill hasn’t enough torque?
Thanks,
MP
Hey Mike,
As long as they don’t stick up more than 1/16″ or so the thinset will compensate for it. If you used the correct screws then it probably is either your drill (if it stops or slows toward the end) or the bit (if it is stripping the screws).
Can you use Redguard behind glass tile? Will the red color show through the thinset behind the tile? If doing glass tile (in a shower), what would you recommend for the waterproofing layer?
Hey Boogamite,
All three of your questions have the same answer – it depends on the glass. Every manufacturer has different accepted or recommended methods with their product – contact them and they can answer all three for you.
In general: yes, you can use redgard behind glass. Yes, the red color will show through unless you use white thinset with full coverage. And I always talk to the manufacturer. I prefer kerdi, but make sure that’s acceptable to them before I do it.
Hey Roger,
You’ve got me this far. Now, I’m about ready to start tiling. Walls or floor first, does it matter? And, as far as the walls go, best place to start. I’ve been told walls first, except for the bottom row, then floor, and install bottom row of wall so the wall sits over the floor tiles. Does this make sense? Your opinion is greatly valulud and appreciated cause….You Da Man….
Hey Mike,
Doesn’t matter. I’ll normally do the floor first and let it cure, then stack the walls on top of it. If you have the time that’s the easiest. But whatever is easiest for you is the proper way.