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 almost a full gallon of Black Jack Ultra 1000 Siliconized Elastomeric roof paint. Would it be acceptable to apply one coat of that, followed by one coat of RedGard, to the cement board in the shower surround I am retiling? Just looking to save $50 if possible.
Hi Dave,
No, it wouldn’t be okay. Elastomeric roof paint is not an approved substrate (which covers anything beneath the layer of redgard) for redgard. I have absolutely no idea whether the two products are compatible, I doubt anyone does. It would suck to find out they aren’t and you need to replace an entire shower in order to save $50.
tiler installed inside shower walls about 1 year ago.He built the 4 ft pony walls himself and screwed them into cement floor.He used the cement backer board and the roll on vapor barrier used thin set then tiles,grouted and after they dried used a sealer.every 2 or 3 months he has come back to repair small cracks in grout and reseal works fine for 2 or 3 months then water gets behind the tiles or grout flows along the shower pan behind tiles runs inside front shower enclosure frame and comes out the other side and water comes out on front left bottom corner on right pony wall. don,t know how to fix this once and for all help!!!
Hi Brian,
He has a slope angle incorrect in there somewhere. All water, whether above or below the tile, should be angled to the drain. Sealer has nothing at all to do with waterproofing anything, it is for maintenance purposes. If he’s relying on that to stop water from penetrating the tile or grout then it’s not going to solve the problem. You need to figure out where (beneath the tile) the substrate is incorrectly sloped. My guess is the top of the curb.
Hi Roger.
I think I have a little situation.
I’m going to tile a ceiling over a tub. Already installed cement board, thinset the seams ( tub walls and inside corners), and primed walls with Redgard. I wasn’t planning to apply Redgard over the ceiling.
Now, whe I said ceiling, I meant a soffit built over the tub area and vertical wall of it, will be painted. The soffit has an outside corner and I installed a metal corner bead on it. Of course I already taped and compounded it to the vertical wall…
So here we go…
1) Am I screwed by using metal on the corner? Hopefully not.
2) Should I use mesh tape and thinset over the metal just like over CBU seams?
2a) And then prime with and use Redgard as anti fracture membrane? Or
3) Mesh tape, no thinset, prime with and use Redgard? Or
4) Rip metal out and use plastic corner bead?
Thanks.
Hi Sebastian,
1. No, not up high like that. If anything it will only see vapor, direct water contact over time is what causes problems.
2. I would mesh tape and thinset, let it cure, then redgard.
Hi,
Great site – I commend you for all the effort involved in this site.
I’m not sure if I am reading this right, but it seems like there are two options for prepping the walls for tiling. I can use a plastic sheet behind the cement-based backer board, or I can wait til the backerboard is taped then use the Redguard water proofing with no vapor barrier behind the backerboard. So how do you decide which method to use? And is there any issues with using the thinset over the Redguard when installing the tiles?
Thanks,
John
Hi John,
There are about 20 ways to properly prepare a shower wall for tile – those are two of them. A topical membrane (redgard) is a more efficient system because your substrate will never get wet. With the traditional system (plastic behind backer) your substrate will get saturated and hold water until the next time the shower is used, it then flushes the water and replaces it with new, but it’s still normally always wet. No issues at all with using thinset over the redgard.
Roger, thanks for the reply. A follow-up: this is probably just a semantic issue, but when you say the substrate [backerboard] gets saturated having the vapor barrier behind the backerboard – doesn’t the tile, thinset, and grout prevent the water from reaching the substrate? And isn’t the vapor barrier meant to protect the wood from absorbing the moisture and ‘moving’? I’ve always heard that cement contains some moisture to stay together and that having a vapor barrier next to the wood is best.
That is exactly why you have the barrier behind it – tile and grout are NOT waterproof. If you have your waterproofing on the face when water gets behind them it immediately hits your waterproofing and runs down into the drain. With the traditional method it first saturates your substrate, then hits your barrier and runs down into the drain.
Roger,
Thanks for your helpful information. My question concerns the recessed niche. I’ve already installed the plastic vapor barrier, but just found out a certain someone wants a recessed niche for the soap. Should I just rip out the plastic and go with hydroban overall, or is it possible to keep the plastic membrane and waterproof the niche with hydroban?
Hi Ryan,
You can cut out your hole for the niche, silicone the existing barrier to the back of the perimeter of the hole, install your niche and hydroban it four inches around out onto the wall.
Did that make sense? I don’t know, I’m tired.
Made sense to me…
You’re fine, that makes perfect sense to me :). I’m assuming I’ll also need to create a dam with silicone between the barrier and the backerboard around the perimeter of the niche, correct? Thanks again, I appreciate the help.
Yes, that was the ‘silicone the existing barrier to the back of the perimeter of the hole’ part.
Hello! Thank you so much for such an informative website! Truly awesome!! I have a couple questions about my current what did i get myself into project. I am tiling the walls around a tub, one of the walls is an exterior wall with a window. The exterior wall is concrete block and stucco. I live in Florida and it is very humid here. I was planning on using durock and then waterproofing it with RedGard. My house has metal studs instead of wood, but there are strips of wood attached to the concrete block to attach the walls A guy at home depot said I could also paint the cement blocks with exterior paint to prevent moisture from coming in from outside.
so my questions are..
1. Is the durock/redgard approach a good choice in this case.
2. Should I paint the cement blocks?
Thanks in advance and I hope I made sense..
Dorothy
Hi Dorothy,
1. Yes
2. No, it will create a moisture sandwich in which mold may grow.
I’m a DIY and could use some advice. I installed Hardee Backer for the shower and didn’t tape the seams before tiling; I used MEIP thin set for 12 x 12 porcelain tiles. Am I looking at problems later or will it be ok?
Can I install 6 x 6 ceramic tiles on my shower ceiling over existing dry wall with stucco; it’s approximately 15 sq. ft. of tile. I’m afraid that the tile will fall out or collect moisture. I was told that there is some special type of adhesive thin set that’s made for tile to dry wall applications.
While in the basement I notice that 3″ x 5″ of my pan liner is showing through the sub floor, and there is a 1/2″ lip along the shower curb were the sub floor is uneven. Should I fix this before laying down 4-n-1 mortar mix, also I didn’t do a pre slope, before inserting the PCV liner. I haven’t poured the cement yet, should I fix this before continuing?
I removed the copper lines and installed PEX lines in the shower, so far no leaks. I have high pressure in my neighborhood would it be in my best interest to install a pressure reducing valve.
I have also put in a shower Niche, what is the best way to waterproof this.
Hi Loyd,
It’s difficult to tell. It may be fine, it may not. If you see cracking of the grout, especially where those seams are located then that’s the reason. Do you mean install tile to stucco over drywall…or install the tile over drywall with the stucco? If you are going directly to drywall any good modified thinset will work – the mapei you used will be fine. If you have stucco on your ceiling it will need to be removed first.
Yes, you need to fix the preslope issue – you absolutely need one. And you should also fix the subfloor issue as well. I don’t see why the pex wouldn’t handle the pressure, you should probably check the pressure ratings on it. Google the Terry Love forum and ask that question there, they’d know better than I.
Can’t get that pdf of Durock’s to read easily on my tablet. Which side, since I am Hydrobanning the walls to the ‘nth degree, of Durock should face inside shower?
Still 1 part Hydroban/3 parts water mixed well for primer coat?
And the Durock pdf seems to be saying…again their pdf not clear…that some sort of inorganic stickem stuff just fine for glueing tile to walls. My neighbors ‘PRO’ just used something like that over tightly abutted sheets of Durock, coated in RedGard. Oh and two days for the stickem stuff to dry under tile before he grouted. He told them thinset was impossible to work with.(How many weeks before they start having tiles falling off in their toes?)
Hi LaNell,
Side doesn’t matter, smooth side is easier. Yes, 1 part hydroban to three parts water for primer coat. Probably about three months or so before problems arise in that shower, may be a year before they can see it, though.
Hello Roger,
I’m using the MAPEI Mapelastic Aquadefense product sold at Lowe’s for my new shower
topical waterproofing, …. have you ever used this brand. After 2 coats cures out
it is a really dark green and my Black Sharpie is way too hard to see any good layout
marks/lines. Any suggestions what I can use to mark on it for my layout lines that will show up good to my poor old weak eyes? I’m thinking some type of speciality pen/marker with yellow or whie ink or paint …… Any ideas??
Hi Bob,
Yes, I have used it. The color depresses me.
Get a silver sharpie, it works well.
Great information on your site! I’m tiling my shower stall and plan to use RedGard over cement board. I know (from your site) to use fiberglass mesh tape on the joints, but what I’m not sure of is: Do I fill the joints with joint compound, thinset or does the RedGard work for this?
Thank you!
Duane
Hi Duane,
You tape and mud the seams with thinset and mesh tape, let it cure, then apply the redgard.
I am over thinking as usual. That tends to freeze me in place. With with a square in one hand, a level in the other and my eyes glued to each posting you have.
On the verge of going for piece of mind and order custom KBRS pan. 5″ wall flanges etc. I assume unless you slap me silly that anywhere it is reading to use polyurethane sealant, that 100% silicone (no, am NOT hooked on the fumes and not because I sold GE stock) is much better ?
Hi LaNell,
You need to use the polyurethane sealant. It is a bonding agent as well as a sealer, so there’s a reason it’s specified.
I am putting red gard over backer board that has been taped and mudded. Do I need to put a coat of primer paint on before the red gard? I have some oil based primer.
Hi Mary,
Not paint primer. Mix two parts water to one part redgard and paint it onto your backer as a primer.
Great information!
Quick question. I have the liner sandwiched between my preslop and my top mud. Should I apply Redgard on the top mud? Or will this trap moisture?
Hi Barb,
It will trap moisture. You can paint it onto your pan about three inches from the wall, but that’s about all you want to do on the floor.
Does Redguard make any preformed shower pans like Laticrete’s?
I was trying to find the best combination of preformed pan, topical waterproofing and drain system.
I was thinking Adco linear drain, Redguard, and some sort of pan that would be compatible. Will Kerdi or Laticrete’s pans work interchangeably with Redguard liquid??
Hi Tauran,
Yes they do: http://www.custombuildingproducts.com/products/shower-installation-systems/prefabricated-bases/redgard-shower-base.aspx
Yes, you can use the redgard with the kerdi or laticrete drains.
Hi,
Is it reccomended to use Red Guard on the shower Floor?
concrete?
Thanks,
Robin
Hi Robin,
Redgard is approved for use in the shower base should you choose to use it.
Roger,
Thank you for the awesome resources on your website.
I am a DIY’er and I am planning on installing a tile shower with a traditional mud pan on a wood floor. I was planning on using a liquid membrane on the CBU instead of a vapor barrier on the stud side.
1) Should I install the CBU down to the floor, not putting any screws for the last 6-8″ (the pan liner will be about 3″ above curb), then put in the second mortar bed in so that it will hold the bottom of the cbu in place?
2) Should I apply Hydroban to the CBU down to the floor or stop about 6-8″ from floor?
3) Should I apply Hydroban to the transition/joint where CBU meets the floor?
Thank you in advance for your response.
Cheers,
Mike
Hi Mike,
1. Yes
2. All the way down
3. No need to, but you can if you want.
I love lists. Thanks.
Hi , Do I have to use thinset over Red Guard or can I use the pre mixed tile adheasive for the ceiling and wall tile installation . Thank You
Hi Russ,
It’s mastic. No matter what they label it.
You need to use thinset, mastic will never cure.
Hey Roger,
Maybe I’m off! I thought I could use the redgard for waterproofing the seams and corners of the denshield. Is there a better product to use for that?
Oh, that’s completely fine. It sounded like you were going to cover the entire wall with redgard, though.
Carry on.
Hey Roger,
Can I use the Kerdi-BAND for the seams on the DenShield?
I will just have a bunch left over from the Ditra on the floor. Wasnt sure if i could just use that instead of the mesh tape.
Thanks!
Neel
Yes.
Awesome site! Your info is such a help.
A few questions:
1. At what point do you place the fiberglass mesh on? During first coat of redgard?
2. You say no vapour barrier. What if insulation is in your shower wall? Do we use that plastic vapour barrier then? Or leave it open and put DenShield (which is what I’m using) directly over it?
Thanks!
Neel
Hi Neel,
1. Yes.
2. Leave it open and put the densshield right over it.
3. (My question): Why are you redgarding densshield?
Hey there you are the greatest info guy out there going for the diy guy. A small questions for you? I built a tile shower and put cement board all the way around I put a waterproofing membrane called the ultimate blue seal the guy at home depot says he use that instead of redi its supposed to be better then redi ? Now I’m worried about the adhesion of the thin set mortar with polymer. The question I’m asking myself is will take to the membrane surface is there something else that I can do to glue he tiles when do I need to rough the surface up so they stick better ??? Could you give me some guidance thanks a million jon
Hi Jonathon,
I have no idea what ultimate blue is. As far as I know it is not a membrane made for tile. If that’s the case then it should simply not be used, no matter what an hd employee told you. If it is tile-specific then just follow the manufacturers recommendations, they don’t want their product to fail.
First off, I love your website! I bought a redi niche… This was my first shower build and I was a bit scared to build the niche on my own with the durrock. It is plastic, but if I paint it with the redgard, do you think I would still have to buy redi’s “special” thinset for tiles to stick to it? I can’t really find anything about redgard over plastic.
Hi Lee,
Redgard will work just fine over it. Just don’t tell ’em I told you that.
: PS : Concerning the 1 inch mosaic tile (glass & marble and tumble marble) for shower floor -what grout do you recommend? Unsanded or epoxy? Do we need to add a non slip coating? Suggestions welcome.
My shower walls are going to be marble with unsanded grout.
I would probably use epoxy given the choice. No, you don’t need to add a non-slip coating.
Jared,
I do not like to clean grout in showers. So, I want to use metal panels to cover the wall instead of tile and grout and thinset for the floor. I will use 3 mil to cover the 2×4 and backer board. 1/8″ gap between the shower pan floor. The liner is 6″ up the wall. How do I need to seal the 1/8″ gap and backer board when I place the metal wall panels ( corregated galvenized metal roof) at the bottom and can the metal touch the shower pan. I want to use a thinset as my floor base for the shower, not tile.
Thank you,
Mario
Hi Mario,
You can use anything you want, because your shower will not last. Thinset is NOT a wear surface, meaning that if you attempt to use it as your shower floor it will not work.
So after installing my mud deck (waited 72 hours for full cure) and using Mapei Aquadefense for waterproofing (three coats), I got to the flood test yesterday. Good news, water stayed put. Bad news, I got some bubbling of the membrane. Very small, but they were pretty much everywhere around the base. I’m assuming this is bad so… First question: what do you think I did wrong? Second question, how do I fix it?
Hi Jared,
That freaks me out. However, it’s actually normal when you have thick layers in there. It’s completely waterproof. All it is is the bottom of the last layer you put in could not fully cure against the previous two coats whereas the top of the last layer did. It is condensation from the liquid membrane itself, not water getting into the membrane. You don’t need to do anything to it, it’s fine.
In your answer to Rene you said you do not want to cover the mud bed with Redguard if you have a PVC liner but just paint out 2 inches. Should you tape and Redguard the bottom edge of the backerboard to the mudbed? Is the reason the same as using vinal sheeting and Redguard on the walls that they will trap moisture between them and cause a problem allowing the moisture to evaporate?
Hi Chuck,
No, you should not tape and mud the backer to the mud bed. Yes, the reason is the same, trapping moisture.