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 am finishing my bathroom and have some questions about the shower. It was sheet rocked throughout.
1) I wanted to know if I can redgard over the sheetrock or do i HAVE to install backerboard over the sheetrock? Do i need to remove the sheetrock?
2) Can I use the redgard directly over the pre-slope without a liner?
3) Will the redgard alone be a sufficient barrier between the pre-slope and the wall transitions?
Thanks!
Hi Matt,
1. No, you can not redgard over sheetrock. You need to remove the sheetrock, replace it with backerboard and redgard over that. Or you can install kerdi directly over the sheetrock.
2. Yes.
3. Yes.
Roger,
I had my shower pan poured with a membrane put under the poured pan and about 2′ up the 3 walls. I finished the walls with backer board and applied Regard over the walls and the floor. Was it a mistake to paint the floor with Redgard and also I was about to use Acrylpro ceramic tile adhesive…Redgard says don’t use it, what should I use on wall tile. I already have Flexbond crack prevention mortar for the shower floor.
Hi Jeff,
It’s not ideal to have redgard there, but it’ll likely be fine. Use regular thinset for the walls, NOT mastic. And NOT the premixed stuff in the bucket that they call thinset – it is just mastic with sand in it. You want the bag of powder that you mix with water.
Hello!
I love your site and have, it’s been indispensable for our current project, which is a steam shower with a 10KW steam generator. I found a very detailed steam shower guide published by Laticrete and have been using it as an overall guide to our project. They recommend a tight vapor barrier on the walls, a PVC pan liner AND their roll on waterproofing membrane on the cement board and final slope. I’m a big fan of logic and you lay out the case against two vapor barriers with perfect logic. However, the Laticrete manual is written for both commercial and residential installations; it’s the guide a government contractor would most likely use. While I’m a fan of logic, I’m also a fan of following published instructions. When the two contradict I manage to loose hours and hours of sleep.
So here is where I’m at: We have a pre-sope, PVC liner and wall vapor barrier up. Once the cement board goes in I’ll it will be time for the roll on membrane. What is your advice regarding the use of the membrane on the floor in this application? I’ve attached the diagram shown in the Laticrete guide.
Hi Rebecca,
I actually only install the hydroban onto the floor about 6-12 inches from the walls. Steam is not going to infuse into the floor, only the walls and ceiling. Keeping that continuous barrier until it is well into the floor is the best option to my mind. That’s how I do it.
That makes sense. Time to charge forth with the next steps! Thanks so much for responding; I have no idea how you manage to do all the work you do and maintain this website…
Me either.
Roger I got your book on using waterproofing membranes and I am installing 18″ travertine tiles with a pre-formed (acrylic) tub. I put up Durock backer board with 1/8″ gap above the tile flange on the tub. I used tape and thinset for most of the in-plane seams but then put silicone caulk between the tile flange and the backer board and also in the corners. The silicone is for granite/stone and claims to be paintable.
I plan to use Mapei Aquadefense and have two questions:
1) Should I spread Aquadefense over the silicone joints and also onto the tile flange, or would it make more sense to use mesh tape or mesh tape and thinset over the seams first to give the Aquadefense something to stick to? I know very few products stick to silicone and I’d like a continuous waterproof surface. Looks like this has come up before as a question but I’ve already put silicone in the corners…
2) My durock boards extend about 1/4″ proud of the tile flange and I am planning to tile down to the ledge on the tub. What do I do with the extra space between the tile flange and tile when I set it? Fill it with mortar? Will that stick to the tile flange, or again would tape help? I think I read on your site that you can set tiles in free space but I am worried that it could be sensitve to cracking in the future and that it might be difficult to grout. Are those concerns misguided?
Thanks!
Hi Devin,
1. It would be best to tape the seams first. Not the backer to tub seam, but the rest of them. Paint the AD down over the silicone and onto the flange. It won’t stick completely, but it will fill in any tiny voids.
2. Do not fill it with mortar. The tile just hangs there, nothing behind it (anything you put behind it will end up cracking out). It will not crack. That space between the tiles is not difficult to grout, and the tile to tub seam gets silicone.
Thanks much Roger, I will tape in the corners over my silicone. Should I do that as part of applying Aquadefense or should those be applied with thinset a day ahead of time and allowed to dry?
Do I leave a “caulk joint” on the tile to tub seam or support the tiles directly on the tub surface?
The day before and allow it to cure first. Just the joint at the tub.
I would use Lexel where the tile meets the acrylic tub. Silicone doesn’t like to grab to acrylic very well. It is sold at Lowes in clear and white. Silicone will hold for a while, but it always lets go after a while. Also, Lexel is crystal clear where silicone is always a hazy clear. I do 20 to 25 showers a year and have been doing them for 20+ years.
I have aa plastic nook in my shower. Will redgard adhere to it?
Hi Steve,
If you rough it up with sandpaper it will.
Hi,
Can I use:
stud – plywood – 3 layers of redgard – tile
Would this be okay? I’ve previously used Duroc with Redgard over it. I’ve always thought that Redgard could be used on anything.
My main reason is that I need to pad the wall out, but reading advice above I can rip pieces for shims. But, is plywood acceptable with 3+ layers of Redgard?
Thanks,
-Parsko
Hi Parsko,
No, you can not. You need a stable substrate behind your redgard, like backerboard. Sorry.
We have plaster walls that have been previously painted. I’m wanting to tile up the whole tub surround.
One forum I found said I needed to remove all of the paint, prior to putting up the redgard or similar product, but I’m not even sure how to do that. Do you think it’s necessary?
Hi Jeff,
It depends on the paint. I would at least sand it down to where you have a rough surface, that would ensure a good grip by the redgard.
I used red quad on purple board. I then used a premium premixed motor from lowes. I found after doing half the tike that I was not to use the or emailed mortors, the tiles are stuck solid to the wall. Should I demo and start over even though I can not pull the tiles off. This is a tube shower unit.
Hi Chris,
Did you cover the entire surface of the purple board with redgard? I would pull one of those tiles off and see if the mastic (premixed mortar) is cured in the center of the tile. It would be my bet that it is only cured around the edges of the tile – that’s why you’re having trouble pulling it off. It’s likely still wet inside the perimeter unless you’ve used small tile like a 4×4 or smaller.
Hi Roger,
One question I have, and rarely seems to be mentioned anywhere:
If tearing or puncturing the redguard membrane is an issue, then how do you trowel it safely? Scraping a metal trowel across the membrane will surely cause a few tiny holes or tears.
If you could advise, I’d appreciate it.
Thanks.
Hi Jim,
You can paint more redgard over any penetrations. If you are puncturing your redgard membrane with a trowel you are using it incorrectly. It will not puncture the membrane when used correctly. You would almost have to swing at it with the trowel teeth to damage it.
How long can I leave a redguard treated shower wall exposed before I have to tile it? I work and am trying to do the job between my days off, and we won’t be using the shower just the tub.
I’m going off the Hydro Ban data sheet and it states that you cannot leave exposed walls up for more than 2 weeks. However, the the main concern is exposure to sunlight and out door weather. I plan on blacking out my bath windows and the shower will be inside an insulated air conditioned house. I’d urge you to find redguards data sheets to learn the specifics if tghe product. Good luck to us both!
Yes, that is only for exposure to sunlight or any UV light.
Hi Richard,
As long as you need to provided it isn’t subjected to any abrasion or wear (don’t use the shower).
My question is in regard to using Redgard on Hardibacker, I have read about many people having issues with proper adhesion due to the hardie being so dry. The install instructions for Redgard seem to indicate that a primer coat (1 part RG to 4 parts water) is recommended with fiber cement boards.
Have you had experience at all with this issue? The primer coat is not mentioned in the instructions for Laticrete’s Hydro Ban, and I have heard the adhesion is better. What liquid waterproofing membrane would you recommend specifically for use with Hardiebacker? Thanks for your time.
Hi Bob,
My preferred liquid membrane is hydroban, but they all work the same over hardi. You want a primer coat as suggested.
I just coated the walls and floor of my shower with the one coat of redgard but already had a plastic vapor barrier installed underneath the duroc backerboard. I just ready the above portion that states I shouldn’t do both. What do you recommend I do? Should I apply another coat to prevent water from penetrating?
Hi Gus,
Nope, leave it and tile it as it is. It’ll be fine.
Instead of the mesh tape and redgard for seams, could I run a bead of silicone?
Hi John,
Yes, but you still need the tape and redgard.
Hi,
I have a 3×5 shower whose base is deckboard covered with durarock then a rubber membrane was layed then a sloped mortar mud floor and adjustible drain. The membrane is sitting flat on the durarock covered deckboard with no slope I want to redguard the floor because I don’t want water to pool in the flat membrane below the mud pan. Did the guy who built the shower make a mistake by laying tha membrane flat beneath the mortared pan instead of laying it on top of the sloped mortar floor? If you use a membrane, is it placed on top of the sloped mortar bed and can it be redgard OR a rubber membrane? Please tell me how it can be fixed:( This shower is in a small stilt house 12 foot in the air and im afraid if i redguard the fllor with the rubber membrane at the base ill get that moisture lock you talk about with the walls. Thanks in advance.
Hi Kristi,
Yes, he did it incorrectly. A membrane is always to be placed over a preslope. The only proper fix is to remove and rebuild the floor with either a proper preslope or build it with a single slope with redgard on top of it. Redgarding over what is there now may cause issues down the line.
Hi, Roger. I am getting a shower installed with Durock cement backer. My drywall contractor taped and joined the seams, including the corners where drywall meets Durock. Now there is some setting-type joint compound on parts of the Durock that I plan to tile over (extending 2-4″ from the edge). I plan to use Redgard before tiling. Do I need to scrape the joint compound off? Or, can I just prime over the joint compound before putting on Redgard?
Hi Vince,
As long as it’s flat you can prime over it.
I have a tub surround and would like to tile from the top of the tub surround to the ceiling. Do I need to rip out the drywall above the surround and replaced with cement backer board? Or can I apply redgard over the drywall then tile?
Thank you,
Bill
Hi Bill,
As long as it’s over 2″ above the shower head you can redgard it and tile it. You actually don’t need waterproofing there (2″ above), but it certainly doesn’t hurt.
Hello Roger
bought your ebooks on waterproofing and tips for tiling showers and found them as helpful as your excellent blog posts. I want to ask a couple of questions to be sure I’m clear on how to handle my current shower project:
1) I can’t find clear instructions on how to handle sealing the joint between the top of my cement backer (wonderboard) and the ceiling (green sheetrock) — my best guess from reading your info would be to use silicone for this gap, but do I also tape it with the fiber tape first? I’ll stop guessing and wait to hear your answer :-)
2) As a novice DIYer, I was following Lowe’s guidance on waterproofing my shower which indicated to do a vapor barrier AND a waterproof barrier like redguard. I was planning on using redguard after filling the seams with thinset which I am ready to do tomorrow in fact — however–
I do have a vapor barrier behind my cement backerboard. I like to be as thorough as possible for waterproofing so could it make sense to redguard the seams, corners and ceiling joint (maybe not ceiling but I would have before reading this blog post) but do not Redguard the face of the boards? Would this allow extra waterproof protection while still allowing room for evaporation, or am I better off not using redguard at all?
Looking forward to your reply and really glad I found your site!
Job
hey, thanks again for your help.
I have my walls up (durock),
first layer of mud bed has been laid,
I wanted to ask
if I am doing a Redguard membrane do I still need a shower liner above the first layer in between the second layer of the mud bed?
if so once I install the liner and lay my second layer, do I then Redguard the top of the mud-bed, then install my tile?
Hi Victor,
No, you do not. You don’t even need a second layer, you only need one slope for a topically waterproofed base.
My contractor is proposing to install a vapor barrier in a shower stall behind the hardee/durock board – it is a brown paper material on one side and the other side looks like foil. Is it still possible to use redguard or the mapei aqua defense on top of the cement board, or is there the possibility for moisture to become trapped as you describe above with the use of plastic. Please advise. Thanks.
Hi Valerie,
It is very possible to trap moisture in there with a topical membrane over the top. I have no idea what that product may be, but it likely isn’t a product made for a shower barrier.
Roger, it is rigid foam. It is commonly used as a R-value insulation to hold fiberglass (pink stuff) off a cinderblock or brick exterior wall to avoid condensation. I’ve no clue what would happen if it were installed on the interior walls. It likely will build up condensate on the foil side if temperature difference between the shower wall and exterior wall is too great and that condensation could cause mold problems if there is no gap or place for the water to evaporate.
Have several rental properties: Have a tub surround where I have to replace the wall down to the studs. I have left over 3/4 ” AdvanTech flooring. Can I use this to replace the wall board around the tub? I will be using Maax polystyrene glue-on panels for the surround. Will this cause any type of water moisture/ mold problem? Thanks for your help. Bob
I have a question guys. Can you tile directly over the redguard (shower pan) flooring? I dont know how I found this site so please email me thanks in advance! JMartinez
Excellent and informative site, thanks.
My question is in regard to using Redgard on Hardibacker, I have read about many people having issues with proper adhesion due to the hardie being so dry. The install instructions for Redgard seem to indicate that a primer coat (1 part RG to 4 parts water) is recommended with fiber cement boards.
Have you had experience at all with this issue? The primer coat is not mentioned in the instructions for Laticrete’s Hydro Ban, and I have heard the adhesion is better. What liquid waterproofing membrane would you recommend specifically for use with Hardiebacker? Thanks for your time.
I have removed a tub surround and want to put tile in it’s place. Some of the top coating on the drywall came off where the surround was glued to it.
Do you know if that can be repaired in any way or do I have to replace it before using the Regard. It is sturdy and in good shape otherwise. Thanks for your help.
Hi Bill,
You can not use redgard over drywall. The drywall needs to be replaced with cement backerboard.
I have taken out tiles, grout, boards underneath the shower bench/seat (this area is about 3 ft x 1.5 ft, not that big), found that builder did not use Cement board, rather following construction method was employed.
Tile + Thinset + Redgard + Green mositure control board + drywall board + studs
Now, i want to do this thing in a right way … since the builder used 2 board each of them 0.5 ” , can I replace the old construction with the following ?
Tile + Thinset + Redgard + Hardie board 0.42″ + Pressure Treated Plywood +studs
Reason for having the same kind thickness for the whole thing is that I cant move the aluminum shower frame.
Question 1 : Can I use Exterior grade plywood in wall over stud, any recommendation on plywood?
Question 2 : Also if Plywood is used do I need to apply a fine layer of thinset mortar on wall also just like they do it on floor ? why they apply thinset between plywood and hardie board in floor ?
Thanks and appreciate your feedback in advance !
Hi Salman,
Just shim out your studs with strips of any type of wood to get your backer flush with where you need it. Since you are using redgard over it the type of ply doesn’t really matter. No need to use an entire sheet over the studs, just rip down strips as wide as the studs as shims.
Roger, got your book, one thing not clear to me, at the change of plane where the side walls meet the back wall do I:
1.) Use silicone caulk wait a day then redgard over
2.) Use silicone caulk wait a day then embed mesh fabric in the redgard
3.) Tape and thinset wait a day then redgard over
4.) Caulk, wait, tape and thinset, wait, then mesh fabric in the redgard
5.) Something else?
Roger,
I have the exact same question – thank you!
Hi Tom,
#3 – tape and thinset, wait a day, then redgard.