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.

redgardIt 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.

RedGard website

Laticrete website

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.

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  • Moo Kahn

    Baloney on the “no vapor barrier behind the red guard “- First – you install poly behind a wet area to prevent LEAKS from rotting out the framing/insulation/whatever is in the wall. It’s the last barrier between a leaking shower/tub and disaster. We install it in such a way that if there is a leak, it can be observed (and hopefully, fixed) by the homeowner before major structural damage occurs. The poly is terminated over the tub flange and would direct the leak to the base of the tile/tub joint. The first indication of a serious leak would be a failing caulk joint between tile and tub flange and an area that never seems to dry up. If you’re seeing that – you have to demo the failing tile and repair the membrane on the tub side of the equation. Second – if the RedGuard is truly forming a membrane – the water won’t get there in the first place – right? Right. “Mold” is the least of your problems if you have a leaking shower pan or tub surround. Rotting studs, sheathing, and floor joists and subsequent termite or carpenter ant attacks are what we’re trying to avoid. Of course – if RedGuard is properly applied (and I do like the 3-coat method) – it’s as good as a solid membrane and done correctly you wont have any problems, there won’t be any leaks, and the whole issue will be moot. But you cannot gauge the importance of uber-detailing a tub/shower every step of the way.

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  • Margarita

    My tiling person applied Redguard today … and she would like to continue the process of tiling tomorrow. I told her I thought it would be best/safest for her to wait at least one more day before continuing. Do you agree?
    I am chemically sensitive and my thought was that it would be good to let the strong-smelling Redguard off-gas for an even more substantial period of time than one day before covering it up, in hopes that if the smell has more time to dissipate, it will have less of a tendency to seep out through the thinset, tile, and grout and be a problem for me. Does the Redguard weaken if you don’t cover it within a certain period of time? And if so, what is that certain period of time? What are your thoughts? PLEASE RESPOND JUST AS SOON AS POSSIBLE … my tile person is raring to go and she’s hoping for an answer from me tonight!
    Thanks so very much!

    • Legacy Bath

      You can tile the next day with no problems. The off gassing due to the chemical reaction/drying agents is usually done in 12 hours depending on humidity. If it is a tiled/poured shower pan, don’t forget to do a 24 fill test BEFORE tiling.

    • Legacy Bath

      EDIT:
      24 hour fill test

      Also, it doesn’t weaken over time.

    • Roger

      Hi Margarita,

      Once cured (24 hours) redgard is inert – meaning it will not offgas more than it does in that first 24 hours. Giving it extra time will do absolutely nothing.

  • Adam

    I’m confused on what to do with my shower project. I put in purple board and joint compound mud already. I’m going to use RedGard and I’m not sure if I need a skim coat layer of thinset before or after the redgard? Then I’ll tile with a half inch thinset but I’m confused about which goes on first? (RedGard or skim coat of thinset) Any feedback would be appreciated. Thanks!

    • Roger

      Hi Adam,

      You don’t need a skim-coat of thinset over the walls.

  • Lyle

    Roger, I just finished Redgarding my bathroom shower mortar base floor after laying down the mortar base on top of a rubber membrane (Oatey). I’m ready to put down the tile, however, you said to Trina in a previous post (about mold smell and other issues)… Hi Trina, Please tell me he installed deck mud (cement-like stuff) over the membrane (rubber liner) in the shower floor??? If so, did he paint Redgard over the entire shower floor as well? Because he should not have. Please tell me how he constructed your shower floor (if you remember).
    …..My question is… I installed redgard over the mortar base which was laid on top of the rubber membrane (Oatey). You said to Trina that he should not have put Redgard on top of the Mortar base. Just to make sure I;m reading this correctly, are saying that – NO – I SHOULD NOT HAVE??? Is this correct??? Tell me now, so I can rip off the Redgard or leave it before I tile over it!!! Thank you Sir!!!

    • Roger

      Hi Lyle,

      No, you should not have put redgard over it. You are mixing waterproofing techniques. You need one or the other, never both.

  • Art

    Hello,

    My tile installer wants to put 10 minute building paper behind HardieBacker 500 for a bathtub surround. Will that be just as good and last at least a long as HardieBacker with RedGuard on top?

    • Roger

      Hi Art,

      Not sure what “10 minute building paper” is – do you mean tar paper? If so then yes, it is an approved shower building method. Is it just as good? It makes your shower waterproof. Redgard has advantages over it, but they both accomplish a watertight shower when installed correctly.

  • Lance

    Hi,
    Putting marble in the shower got a heck of a deal. What thinset would you use over redguard? Thanks for any advice.

    • Roger

      Hi Lance,

      Any good modified thinset will work fine. I would use Laticrete 254 or TEC 3-n-1. But nearly any good thinset will work fine.

  • Ben

    Hi Roger,

    I am doing my washroom and used cement board for the walls and applied redgard. However, I did not wrap the shower door frame with anything. Can I apply Redgard over a shower door wood frame and tile after? Thanks.

    • Roger

      Hi Ben,

      You can, but the tile won’t last. You need to have some sort of approved substrate (cement board) over the wood. You can use 1/4″ for that if you need to.

      • Ben

        Thanks Roger.

  • Joe Lashomb

    Hi Rodger,
    I had a sub contractor do a shower for me, he installed greenboard for my tub/shower surround. Mud taped seams and red guarded the surround. I arrived back from vacation before he tiled it and informed him you can’t put red guard over greenboard. After 1 firing and a lot of profanity I need to come up with a plan.
    Can I install Kerdi over the red guard with unmodified or tear it out and use Hardi-backer ?
    Signed
    Frustrated in NY

    • Roger

      Hi Joe,

      You can do either. You can install the kerdi over the redgard, it would be easier.

      • Joe

        Thank You !

  • Richard Duyck

    Hi Roger ,
    Building a shower following your manual for topical liquids for floor and walls. I’ll be using Redgard. Their site says to use fiberglass mesh at drain and for extra protection at corners and change of plain. What type of fiberglass mesh are they talking about, the same I used at cement board seams? Or drywall fiberglass mesh? They recommend a 12″ square piece at drain. Any ideas for drain area. I’m using recommended kerdi drain.
    Also is the proper thinset for tile over Regard, modified thinset? Thanks for all the help.
    Rick

    • Roger

      Hi Rick,

      Yes, same mesh used for backerboard seams. Yes, modified thinset over redgard.

  • Greg

    Hi Roger,
    I am installing a shower. I thought I would use a Ditra sloped substrate and a ditra drain. I would bed the substrate in unmodified thinset, as recommended. Then use a thinset to fill the substrate cells and waterproof with a liquid membrane. Does that sound reasonable? Should i use unmodified or modified thinset to fill the substrate cells?
    Thanks

    • Roger

      Hi Greg,

      Ditra is not for showers – kerdi is. There is no such thing as a ditra drain. You need a regular deck mud bed, with a kerdi drain, covered with the kerdi membrane. Not exactly sure what you have planned here – can you clarify a bit?

      • Greg

        Roger,
        Thank you for responding. I will try to explain my project better. I would like to install a KERDI-SHOWER-ST tray and a KERDI-DRAIN. Bed the tray on the plywood subfloor with unmodified thinset mortar and then fill and top the tray with thinset, I then intended to use a liquid waterproofing membrane to install the drain and cover the thinset on the tray. I would then lay tile on the waterproof membrane. Should the thinset filling the tray be modified or modified? All walls are cement backerboard which i would also cover with the liquid membrane, reinforcing all seams, corners etc with fabric. KREDI shows the tray bedded in thinset on plywood, should I install roofing tar paper first as I have seen in traditional mud beds? Just a untraditional house situation here. Project sound reasonable?
        Thank you again!

        • Roger

          Okay. You do not need the tar paper, that is to prevent the wood from sucking moisture out of deck mud. Go straight to the plywood. You don’t really NEED to fill the top of the tray with thinset, those indentations are less than 1/16″. You can use modified to fill them if you want to.

  • Brian

    If I use the trowel method of applying redguard, I applied the first coat using a v-notched trowel. On the second coat I filled the valleys with the flat side of the trowel. When the second coat tried I still have ridges ( I presume due to the redgaurd shrinking). Is this normal? Or do I want the dried redguard to be flat/smooth?

    Thanks!

    • Roger

      Hi Brian,

      Unless the trowel is evenly notched (i.e. 1/32×1/32×1/32) then you will still have ridges as the redgard you put in between the ridges is not the same size as the ridges themselves. It’s fine, it doesn’t have to be smooth.

    • Moo Kahn

      If you install RedGuard with a notched trowel – you do NOT LEAVE THE NOTCHES THERE TO DRY. That would give you hundreds of shreds of membrane and not a unified membrane. RedGuard wants to you spread with the notch – THEN turn your trowel around and smooth out the notches completely. Watch the RedGuard video on YouTube . Notched trowels are used (generally – with any material) to meter the amount of material going on the surface. In the case of RedGuard, you’re ensuring complete coverage and the correct thickness when you *turn the trowel around to the flat side* and smooth out the coat. NEVER, EVER leave the “ridges” to dry – if you do you’ll need to essentially start over with your second coat – and you WILL need a third coat for sure. Comb the notches… then turn the trowel around and smooth out the coat into a continuous membrane.

  • Rob

    After putting Redgard on my shower walls, I realized I did a terrible job filling the gaps between HardieBacker boards. I had tried to feather it out from the seams, but I put way to much material on the walls and have ended up with buildup in these areas, which means my walls aren’t flat. Would it be okay to put a skim coat of thinset on the walls to make them flush? I would let that dry, then tile the walls. (BTW, I don’t think it matters, but the Redgard has been on the walls for about a year and a half now. I’m doing a whole house remodel and am just getting back to this.) I just want to make sure the skim coat will bond nicely to the Redgard and that subsequent tiling will bond to the skim coat.
    Thanks for your help!

    • Rob

      Actually, I’ve just looked over the wall again and am now thinking about skipping the skim coat and am wondering if using deeper notched trowel to set my tile might help. Looking forward to your thoughts!

      • Roger

        Hi Rob,

        Yes, a larger notched trowel is exactly how to resolve that issue.

        And yes, I realize this reply is likely too late, but the info will be here for others in the future. Sorry for the delay.

  • Aaron

    Hi Roger,
    I wonder if you’re still around. Hope you’re doing well.

    Does anyone know if RedGard over mesh tape which didn’t get fully embedded in thinset will work?

    Should I skim thinset in the corner or run a bead of caulk down corner before applying RedGard?

    Thanks guys.

    • Roger

      Hi Aaron,

      It will work, but it would be better to cut out the part that is loose and patch over it with another piece.

      And I’m fine, just trying to catch up on stuff – I’m friggin’ slow like that. :D

  • Colleen

    Hi Roger

    I have searched your site, so I don’t think I’m asking something you’ve already answered.

    Would you please elaborate on using Redgard as a crack isolation membrane? I really appreciate your more technical explanations for how things work.

    I’m going to be doing some smaller tile floor areas, not bigger than 5′ x 5′, which are slab on grade in new construction with no pre-existing cracks. One of these areas is a bathroom floor. I know I can tile directly over the concrete but I seem to remember reading that you recommend Redgard over the concrete. Since the cost would be minimal I don’t mind doing this even if you consider it an optional step.

    Thanks! I’ll sit here with my recreational beverage while awaiting a reply.

    • Roger

      Hi Colleen,

      A layer of redgard gives the layer below the tile a ‘buffer’ which can stretch or conform (to a small degree) as needed. What this means is that when (not if :D ) your concrete does crack the 1/32″ or 1/16″ of movement on each side of that crack (allowing it to open) will stretch the redgard without transferring the movement up through the tile. The stress is on the redgard, not the tile.

  • Raynaldo Ramos

    Can you use a non skid water proofing paint over redgard

    • Roger

      Hi Raynaldo,

      No. Why would you??? Redgard is not a wear surface, it needs something installed on it. That being the case, you wouldn’t be sliding on it.

  • Trina russo

    Hello, I had a company tile my shower walls with 13×24 porcelain wall tile and flat mesh rock tile on the shower floor. The setting materials used were Tec mp thinset. The plumber installed a rubber pan. The tile installer then installed the cement board, and used the red guard. Several months later I am smelling mold, and seem to be getting a white residue on the
    Bottom two rows of tile.

    • Roger

      Hi Trina,

      Please tell me he installed deck mud (cement-like stuff) over the membrane (rubber liner) in the shower floor??? If so, did he paint redgard over the entire shower floor as well? Because he should not have. Please tell me how he constructed your shower floor (if you remember).

  • JJ

    We are having our shower retiled. I am in California, and there seems to be disagreements about the right way to build the tile shower walls.
    Their plan is: Purple board, RedGard, Aquabar, Metal lath, 1/2 mortar followed by the tile.
    When I look online it seems that you should use Cement board not purple board. Would there be an issue putting RedGard then aquabar? Is there any issues with the way they intend to install it in your opinion? My husband and I don’t feel confident about the proposed process.

    • Roger

      Hi JJ,

      You state mortar after the metal lath, I’m assuming you mean wet mud, as in mud walls. If so then the plan is fine. There is no real reason to have the redgard in there, but it won’t hurt anything. Nothing is going to get to the purple board. We used to do mud walls with drywall behind tar paper – no issues with that method at all because water never gets back there.

  • Pasquale

    Great tips on tiling. I am doing the shower myself(except the plumbing which a pro did) I want to waterproof as you describe with the Redgard. Does that go directly on the backerboard? Can you coat the studs too? And can you coat the floor(plywood) under the shower pan? I also used waterproof screws(green ones) in the backerboard. Any help is appreciated!

    • Roger

      Hi Pasquale,

      It just goes over the top of the mud bed and over the backer. No need to put it anywhere behind that – water will never get there if it’s properly installed on the face of the backer and top of the mud.

  • Julie

    I put redgard on mortar shower base but don’t want to tile it as too many tile shapes every where. Is it possible to put granite grip on top, or maybe paint then coat with anti slip? Any ideas?

    • Roger

      Hi Julie,

      Redgard is NOT a wear-layer, it must be covered with a hard surface – like tile. I don’t know what granite grip is, I assume some type of roll or paint on product to give the surface grip. You (or I) have no idea at all how that will react to the redgard, or whether it will even bond. No, you can not paint it, the paint will not bond well and water will wash it off.

      Tile your floor. :D

  • Dan

    Hi, we just had a small 8′ x 10′ indoor therapy pool installed. Red Gard was used as a mold preventative on the drywall in the room where the pool is (under the flooring) The smell in the room is very very strong and unpleasant, and hasn’t gone away yet, 2 months later. The RedGard is not covered by tile or anything. I am very concerned for my health with the room smelling so bad. I don’t know about the toxicity of the product or the effects on the respiratory system. Any advice would be greatly appreciated.

    • Roger

      Hi Dan,

      Redgard does not have any VOC’s once cured, it is inert. If it is not covered with tile then yes, you’ll be able to smell it, but it isn’t at all detrimental to your health. Why hasn’t it been covered yet? Redgard is not a wear-layer, meaning it has to be covered with something, preferably tile.

  • Ryan

    You talk about using this as a waterproof membrane, but they also state that you can use them as a crack isolation membrane (at lease redguard states as such). Question is, would you reccomend it as such and if not what would you do instead? I am tiling a family room with a concrete slab floor that has some very small hairline cracks, but nothing significant.

    • Roger

      Hi Ryan,

      It would be perfect for that. The original intention for redgard was as a crack-isolation membrane. Waterproofing has become the norm, but it was actually developed for scenarios exactly like yours.

  • Nathan

    I used regard in my shower remodel, and applied caulk to the bottom edge of the backer board, bridging from the regard to the tub rim. When I install the bottom row of tile, do I need to use more caulk between the bottom of that row and the tub, or would that create a hazardous moisture trap?

    • Roger

      Hi Nathan,

      Once you’re done with the installation you want to put a bead of silicone around the bottom between the tile and tub, but you want to be sure to leave weep holes so that any moisture that makes it’s way down will have a place to drain into the tub.

  • Sharon Schander

    We took out a bathtub and are making a walk in shower. Due to the tub drain being too low for a shower we had to raise the floor 3″. They put in the concrete and did the correct slope for the new drain. We were told at the tile place at it is best to use Redguard on top of the concrete as a waterproofing method. Now we need about an inch to reach the top of the drain. Can we put a 1/2 mud pack down and then thin set to set the tiles? What would you suggest at this point. Our tiles are only 3/8″.

    • Roger

      Hi Sharon,

      You can put 3/4″ of deck mud down, then redgard. Did they put a topical drain in there? Because if it’s a regular drain with weep holes you need to do something different.