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.
Understand everything about the install but just want to make sure about something… the moisture sandwich, I’m not using plastic behind the hardiboard but I’m planning on using tar paper behind it. Does the tar paper act the same as plastic and hold the moisture in when Redguard is applied over the hardiboard or am I over doing it.
Hi Cliff,
You are overdoing it. The tar paper will cause the same issue, it’s actually a better barrier than the plastic (the pores close up when subjected to moisture, so it gets ‘tighter’). Just use the redgard only.
Similar situation to one above in that I have removed old tile and wallboard down to studs in an existing tub enclosure and will be putting up plastic vapor barrier (plastic) under cement backer board. But I’ll be installing tile from tub all the way to ceiling that includes some area above old tiled area where some existing drywall remains which has been painted with semigloss. What prep does the semigloss need? Should I just skip the plastic, and just lightly sand the semigloss before brushing/rolling on Hydroban or Redguard over the backer board and semigloss?
Sounds to me like you’ll need to remove the existing drywall and replace it with cement backerboard everywhere you’re going to tile. Most drywall “paper” is not sufficient for tile. I’d think it would be much easier to do this now, than have to come back later and re-do the drywall, not to mention possible water damage and mold / mildew behind the drywall. When I built my shower in my upstairs addition a while back, I was advised to install 1/2 osb first to help provide a stiffer backing, so leaning against the wall wouldn’t cause the backerboard to “give”, possibly breaking the grout lines / tile, which I did.
After I put up the backerboard, I applied two complete coats of RedGard, onto which I applied the tile using thinset. Cement backerboard itself is rather rigid, but the osb provided extra rigidity. If there are any cracks in the grout, drywall paper can wick it through to the drywall itself.
Hi Ray,
If you use the plastic you just need to rough up the paint with sandpaper. If you use the topical membrane do the same before installing it.
Hi Jedi,
You should remove it all and start over. The backer on top of the drywall is going to create a lip at the edges you’ll need to deal with. You can paint redgard over it, but I really would just begin again and do it all properly rather than trying to band-aid it.
Can you tell me if Green board on shower walls coated with two coats of Redgard is going to work as a waterproof barrier behind tile in shower or should it be pulled out and start over?
Thanks for your help!
Robin
Hi Robin,
It needs to be removed and replaced with backerboard. Greenboard is not an approved substrate for redgard or anywhere in a shower.
Hi Roger,
In the past, I’ve always used the traditional method with plastic behind Hardibacker. This time around, I plan on using a topical vapor barrier for a shower surround.
I haven’t seen anyone comment on this, so it’s possible it’s a non-issue to be concerned about. But have you ever damaged your cured membrane when using a trowel to apply tiles? How durable are these membranes? Should I back-butter the tiles to avoid the potential of scratching a hole into the newly applied Redgard/Hydroban? Is there a trick?
Thanks for you help!
Hi Greg,
Unless you are stabbing your membrane with the trowel you won’t puncture it.
Using a trowel to spread thinset in the normal manner will not affect the membrane at all.
Roger,
This is getting serious! So many questions, and so many answered!
Here are a few more that are just eating me alive!!
I’m building a shower and mud pan.
I’ve read through your mud pan several times. Love it!
I want to use hardi board for the walls. And I was planning on red guarding the whole enclosure (also includes a soap niche)less the finish deck mud.
I prefer you option of liner, installing the backer 1 ” off liner , and decking the backer in to hold it in place.
I notice in your post also to install a moisture barrier behind the backer and over the liner. Makes sense. But with using red guard we don’t want to make the vapor barrier sandwich . So don’t use a vapor barrier behind the backer. My real concern is that the moisture from the deck mud after a shower will get wicked up the bottom of the CBU.
Is this not a concern, Vapor barrier behind or in front?
The pre slope is there, but it seams to me that the mudd would have to fill up with moisture like a sponge, also infecting the CBU , before it would gain enough volume to hit the liner and make it to the weep holes.
What do you make of all this nonsense?
Am I overthinking this?
Looking for your professional opinion.
Have you run into this problem during any demo/ discovery ?
Rotted lower portions due to CBU being set in deck mud.
Last- met a tile setter who says he’s been in the business for twenty years, and has been using mastic in showers. That’s still a no no isn’t it?
Thanks a bajillion
Greg
Hi Greg,
If using topical on the wall with traditional on the floor there should be a gap between the top mud deck and bottom of the substrate to prevent wicking (1/4″ is fine). That said, I still believe that as long as your substrate is NOT touching the horizontal portion of the liner you can still embed it into the top mud deck, but I’ve taken a lot of shit for that. I still stand by it, though, because I’m a stubborn bastard.
Yes, that’s still a no. You didn’t meet a tile setter, you met a handyman with a trowel.
Hello Roger – – does your book cover Steam Showers? Thanks.
Hi Jim,
I do not have a book that covers steam showers yet. It is a specialized application. If you search ‘Laticrete steam rooms’ you’ll find a pdf that describes the build of one with liquid membranes.
Excellent website, very informative, thank you. I have a basement bathroom, 2×4 wood studs, open faced insulation, pre fab shower base. I have installed 8″ wide Vycor rubber self stick membrane (window sealing tape) over shower pan lip and on the inside corners from the shower base to the ceiling. Then 6mil plastic over vycor/shower lip up the wall BUT stopped 2′ from ceiling. The plastic was then covered with Hardie Backer(HB).
So here is my list-
1-Can I put Red Guard on the HB or will still cause a mold sandwich even if the pastic is 2′ short of ceiling?
2-Or just install tile (subway tile) over the Hardie Backer
3-A niche has been added, I know I will have to cut into the HB and support. If I go with a premade plastic niche, do I Redguard and mesh tape the seams or thinset/mesh tape the seams
Your expertise will be much appreciated.
Hi Wayne,
1. I would not. It’s not a matter of allowing dissipation at the top. You can still trap water between two plain sheets of plastic laying on a table, even though the sides are open. Water only evaporates off a surface then becomes vapor which dissipates through open air, it will not become vapor and dissipate upwards through your backer.
2. Just install the tile over the hardi.
3. You need to thinset and mesh tape the seams, then cover with redgard once it’s cured. The thinset and mesh locks it in, the redgard waterproofs it. You need both.
I am remodeling my shower. I have torn out the backer board down to the studs. I am keeping the tile floor. I plan to put up Durock and then Redguard over the walls and the existing floor before tiling.
When the cement board was removed it left a channel all the way around between the existing tile floor and the shower liner.
My question: Since I am using Redguard can I fill that channel with mortar to end up even with the existing tile floor and then put up the Durock on top or must I put the Durock back in that channel and fill any gap with mortar.
I want to fill the channel with mortar but don’t know this will affect the shower liner. Help!
Hi Jo,
You can fill it with mortar, it’ll be fine.
Roger,
Thank you so much. You have just made my life easier. I am off to finish my shower..
Roger,
We are creating a barrier-free shower in a very small bathroom. For reasons having to do with substrate and clearance, my contractor seems to be forced to use a 3754 TileRedi pan to form our curbless shower. The pan will take up 1/2 of the floor, thereabouts, and the rest of the floor will be formed by cement board. We will tile the entire floor with the same 1″x1″ carrara marble throughtout.
He is placing it on 3/4″ ply and 1/2″ cement board, and setting the pan with mortar (I believe that meets your recommended subfloor depth of 1-1/4″). The rest of the bathroom floor will be the same substrate but with thicker ply, so that cement board is brought to the same level as the pan. The joint between the two will be fiberglass mesh. He wants to seal the whole affair with RedGard, including the concrete-board floor outside the pan and all walls both inside and outside the shower pan area.
The pan manufacturer requires a special adhesive for adhering the tile to the pan. The RedGarded areas call for the use of thin-set mortar. Will the two different adhesives cause any problems? Can the RedGard be painted over the pan surface, thus allowing the use of thin-set?
Ugh.
Hi David,
He can use redgard over the pan and use thinset, or use both materials where appropriate. They will both work just fine.
I have a basement bathroom that has been striped down to the cider blocks and studs after a mold remediation. Should I apply Redgard to the cider blocks AND the cement backer-board? Or just appy Redgard to the cement backer-board? I am concerned that in the first scenario I would be creating a place for mold to develop as moisture could not escape the two layers? I am not planning on putting up tile but fiberglass walls. Thanks
Hi Dave,
If you are putting up fiberglass walls you don’t need redgard on any of it. The fiberglass is your waterproofing.
If the hardibacker seams aren’t taped with the mesh and thinset prior to waterproofing with RedGuard, does the waterproofing work? Contractor said he was going to use mesh and thinset when he installs tile AFTER waterproofing with RedGuard.
Hi Stephanie,
The waterproofing will work just fine, but you’re negating any effect of the tape at that point. It needs to be done before redgard or it’s useless.
Is my barrier or barriers there to protect the Duroc or studs?
If Duroc, why would you ever use a membrane underneath the Duroc?
Ever used CertainTeed MemBrain?
They say the fact that it’s a slightly semi-permeable will let any water that makes it under the substrate evaporate.
Could you use Redguard on top and it underneath a substrate?
It is there to protect the studs. CertainTeed MemBrain is not manufactured for that application. I have no idea whether it will work or not. I would not use it.
I used Aquabar on the walls behind hardibacker. I did not run it all the way to the ceiling, the top 19″ is drywall. I was going to to use RedGuard to seal the seems and screw points. Because the walls were formerly garage walls, they (the studs) were not consistant, or plumb. So I have 1/2″-3/4″ shims behind the Hardy backer (to plumb everything up). If I cover all the Hardy backer with Redguard, is it still going to create a seal? It’s sandwiched, but it’s more like a sandwich with lettuce and tomatoes. The gap allows it to breath, No?
I am concerned I did not install the Aquabar properly. (It’s been well over a year so I do not remember) I thought the Redguard was the answer to my problem. Obviously now that I am more informed, I think I have created a headache.
Hey Ted,
I think you’ll be fine going over the hardi with redgard.
“sandwich with lettuce and tomatoes” NICE!
Hello!
I hope you have not abondoned this site and that you still respond to emails.
Where i am in my shower installation is I have taped and mortared hardiebacker on the walls. Soon (in a few days) i will be applying hydroban from laticrete. The tile i will be installing is large format porcelain. i have not lain tile before and expect it will be difficult to obtain professional looking results but not impossible. I really really believe i will need the assistance of battening to help me get the first rows true, but the batten screws will puncture my hydroban. So… am I to inject 100% silicone into the batten screw holes after removing the battens but before laying the tiles that cover the area under the battens? Is there a method better than battens? Do you know anyone who has TileTracker?
Can you also advise me on what mortar mix to apply the tile to taking into consideration it will be over hydroban and the tile will be heavy? I want quick adhesion for supporting the weight of the tile and good glidability. (sp) My current understanding is large format (any edge longer than 15″) tile does not get set with “thinset” but medium bed mortar and hydroban needs a polymer fortified or latex fortified mortar. I’ve seen in their literature specifying one in the data sheet for the drain and one in the data sheet for the membrane. I’ve read in your postings that you use redguard in your work, not hydroban; will you have to perform outside research for this? I apologize for any extra work.
Thank you for taking care of me, Roger.
Hi Persia,
I have not abandon the site, why would you think that?
You can use silicone or hydroban in those holes, or a combination of both. Whatever makes them waterproof again. I do not use redgard much, I use hydroban a lot. You can use a medium-bed or a thinset, either will work. The reason for the medium bed is mostly for floors, the extra sand in it prevents the large format from sinking as it cures. Any good modified mortar will work. All medium bed mortars are modified. I prefer laticrete 254.
Dear Roger
I know you seem to lean toward Hydroban over Redgard for topical waterproofing, right? I’ve not bought my bucket of either yet but did buy the proper trowel to use Hydroban. Just received by email a ‘notification’ (advert/propaganda/whatever) claiming Redgard to be oh so superior to Hydroban. Your take on this? I don’t think I can attach it, the PDF, here but could send it . (communicating with a phone this way is really beyond my tech prowess)
Thanks so much as always
Hi L,
Yes, I prefer hydroban, but redgard is very good. The notification you received was simply advertising created by people who have done nothing with tile except walk on it. It’s a good product, they both are.
Roger,
I’m remodeling my master bath, we tore everything out and down the to studs… The sheet-rock guys came through and they installed DensShield in the shower but seem to have taped all the corners and seams with regular drywall mud… I planned to coat the shower with Redgard but now I’m concerned.
Can I just coat everything with Redgard or do I have to tear it all out and use cement board?
Hi Aaron,
You can coat it with redgard, just make sure you get the drywall mud covered REALLY well.
Roger,
We are in the process of remodeling a tub bathroom. All the walls surrounding the tub were stripped down to the studs. So far the following has been done:
1. Insulation was applied to all walls (1 facing outside the house, 2 are not)
2. Stucco mesh paper was installed (chicken wire with black paper)
3. Coat of cement was applied (cement with sand, no grabble)
Next hardie-backer board will be installed. Porcelain tile will be the final phase. Question is, you’ve mentioned not doing a double insulation as it may trap moisture. Does the stucco-mesh with “black” paper count as a barrier?
My plan was to apply redguard (or equivalent) to the hardie-backer board before installing the tile.
Your input is much appreciated.
thank you,
Hank M.
Hi Hank,
Why?
What I mean is why the tar paper, wire and cement if hardi is going to be used? With the wire and mud between the hardi and tar paper you shouldn’t run into a problem with the redgard, it’ll be fine like that.
But why?
We were initially told to use greenboard around the shower – would Redgard be enough to waterproof the walls before tiling? The greenboard has been installed & now people are saying we should have used cement board, but we are hoping we don’t have to take down the greenboard after all the time and work that went into putting it up. Your input would be appreciated.
Thank you
Hi Michele,
No. Greenboard is not a sufficient substrate for either a shower or redgard. It needs to be removed and cement backer put in it’s place. Sorry, I know that isn’t what you wanted to hear. You can use kerdi over the greenboard if you want, but that’s it.
Hello,
Would painting RedGard over greenboard be sufficient for waterproofing the shower before tiling? Thanks!
Hi Luke,
No. Greenboard is not a sufficient substrate for either a shower or redgard. It needs to be removed and cement backer put in it’s place.
Roger,
I have a shower I am remodeling. One of the walls is the exterior wall, it has insulation and plastic over it. I was planning on using Hardie backer board with Redguard on the Shower wall. Will this be problem with the plastic on the exterior wall and Reguard on the other. I plan on putting Redguard in the whole shower.
Dave
Hi Dave,
I usually just cut a slit in the plastic the length of the stud bay. It doesn’t need to be removed or have huge parts of it cut out, you just need to not have the substrate totally sealed in with the two barriers. The slit allows vapor to dissipate when needed.
Hello Tile-Elf,
Your PDF guide is excellent and a great go-to resource for newbies like me.
Here is my question: I removed a fiberglass surround and installed hardibacker in its place. Per James Hardie’s suggestions I left a 1/4″ gap between the bottom of the HB and the tub’s flange. The height of the HB is 72″ but the wife wants to run the tile all the way up to the ceiling (another 2 ft. at least). I don’t want to do this buy hey, what can you do?
So, I plan on using thinset morter on all the joints, including the transition to the existing drywall and then embedding fiberglass tape into the thinset.
I will use redgard to cover the HB. I don’t plan on applying it to the drywall (which is painted, by the way). Here are my questions:
1. Can I install tile above the 72″ on the existing drywall. It will be unlikely receive any direct water hits. Or, should I continue the HB all the way to the ceiling(please say no!)?
2. I am going to seal the 1/4″ gap at the bottom with silicone sealer. Is that OK?
3. There are some areas, particularly where the old drywall meets the HB, that are a little uneven, maybe by an 1/8″ in some places. I am concerned this will cause issues when placing the tile. Is it possible to do some feathering with the thinset? Or just play with the the thickness of thinset when I apply the tiles?
Thanks,
Kurt
Hi Kurt,
1. Yes, you can install tile up there directly to the drywall.
2. Yes, provided you install it, wait for it to cure, then go over it again to ensure you don’t have any open areas.
3. A combination of both would be best. If it’s only 1/8″ keep in mind that you should have somewhere around that amount of thinset behind your tile once it’s installed. It’s easy to adjust your tile over that amount of inconsistency with just the amount of thinset under your tile.
Not to beat a dead horse, but…. I put plastic on the existing floor and poured a cement mix on top sloping it to the drain. Kerdi was put on top of this all the way to the drain. My big mistake, other than not using the Kerdi drain was that I did not seal the Kerdi to the drain ring but rather tucked it in and placed the top ring of the conventional drain on top of that. I believe this led to a gap that trapped water and finally destroyed the silicon “seal” I put around the circumference.
Now, replacing with a Kerdi drain, would you put the drain on top of the existing Kerdi and seal with Kerdi Fix or Redgard or strip off the existing Kerdi, set the drain and return the existing Kerdi to the top of the drain assembly???
The whole floor in the bathroom is covered with Kerdi and the shower is a no hub, no enclosure made for ez access.
Hi Mike,
I would cut an 18″ square with the drain centered in it, install the drain, then place a 2′ square piece of kerdi over it to patch it.
Roger-
I have a exterior window in my shower and is pretty deep which is nice because it also acts as a bench. The flashing tape adhered to the window framing extends in about 4-6.” I’m using topical moisture barrier and read that I shouldn’t add topical moisture barrier when there is a moisture barrier underneath the substrate. Does this count for flashing tape as well? Should I just add the topical barrier up to the point where the flashing starts?
Tracy
Hi Tracy,
No, it doesn’t apply in that application – paint it right up onto the flashing.
Used Kerdi to make a shower pan-Cement with slope, Kerdi on top. Used the conventional shower drain, however. Siliconed the perimeter of the drain and all was fine for about 2 years. Now, water is seeping in causing a leak into the ceiling below. I know you like lists, so,:
1> can I seal the perimeter of the drain with RedGard) taking off surrounding floor tile and coating with RedGard , the exposed cement slope as well as down to the plastic surface of the shower drain?
2. Should I tear out the drain and replace with the Kerdi drain kit?
Saved the $100 on the original drain, but, then again got an education in drainage. LOL
Thanks
Hi Mike,
I would strongly recommend replacing it with a kerdi drain. The redgard may work, and it will seal it, but I don’t know how you have the drain set up (divot method? Top slope over the kerdi?) so I really can’t say whether it will work or not. Go get a drain, why learn the same lesson twice? (It’s not that bad, I do it ALL the time.
But it does get expensive…)