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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  • David Maxwell

    Should a fiber based thin set be used on a shower wall that has been treated with Regard?

    • Roger

      Hi David,

      I have no idea what you mean by a “fiber based” thinset. A modified thinset should be used over redgard. Is that what you mean?

  • Adam

    I’m installing a Redi Tile shower base which will be tiled with square ceramic tile up onto the flange. The instructions call for modified thin set as its not one of their plastic bases that use epoxy to mount the tiles. I do not intend to tile the walls, which will be covered with FRP panels. I would like to redguard the new Green board walls and the base before tiling.
    Two questions. Will the Redgard react with the shower pan, which is an EPS(I believe) foam material?
    Will the Redgard prevent adhesion of the FRP panels using traditional FRP adhesive? Is there a specific panel adhesive that would be best for adhering over Redgard?
    Thanks. -Adam

    • Scottie

      I asked the same question regarding the Redi Tile shower pan that I installed I did not red guard the shower pan I did use the epoxy adhesive to tile it advise that I got was to not red guard it as it was already water proof.

      • Adam

        Was your Tile Redi base a hard plastic? Ive seen pictures of them that look that way, but my base is EPS foam I believe and the instructions don’t mention epoxy for the tile as I saw on the plastic ones, but rather it says to use modified thin set to set the tile.

        • Scott Adkins

          No definitely not hard plastic very lite probably not more than 30 lbs installation instructions said to set it on a mortar bed and supplied epoxy adhesive for the tile.

          • Roger

            The plastic redi-pans that require epoxy are not a ‘hard’ plastic, and extremely light.

        • Roger

          Plastic needs epoxy, foam uses thinset.

    • Roger

      Hi Adam,

      It will not negatively react with your tile redi pan (but don’t tell them I told you that :D ). As far as the frp I honestly don’t know what to use for adhesion. I assume the regular adhesive will work just fine. Maybe get a scrap piece of drywall or something and test that out? I see no reason why it wouldn’t work.

  • DoubldD

    Can you apply Redgard directly to wood (like2x4 or plywood) for a shower shelf (no Wonderboard)? Will it provide enough water resistance to avoid water damage?

    • Roger

      Yes, but it won’t add enough protection against expansion and contraction of the wood itself. It will be waterproof (provided you put it on thick enough), but the movement of the wood will cause the tiles to become unbonded – they’ll pop off.
      So…don’t do that. :D

  • Lacey

    I just ripped out the old tile and sheetrock from my shower and found a black plastic vapor barrier stapled to the studs over the insulation. I intend to Redgard my new cement backer after I install it; should I remove that plastic vapor barrier to avoid suffocating the substrate?

    • Roger

      Hi Lacey,

      Yes you should.

  • Zac

    Unmodified or modified thinset over Redgard in shower walls and ceiling?
    I would much rather use modified because it is easier to work with, and in my opinion sticks better, but I am being told you shouldn’t use it in a shower because moisture breaks down the polymers in the modified thinset over time. Also, I believe modified takes longer to cure and requires aeration, and with Redgard being an impervious layer I feel will not allow it to aerate properly to cure. But will unmodified thinset be weaker and not properly hold the tile over time, especially on the ceiling. Using 12×12 tile. Seems there’s pros and cons to both. I just want to do the right thing.

    • Roger

      Hi Zac,

      Modified. Redgard is designed and formulated to enable modified thinset to correctly cure. It calls for modified thinset.

  • Carla Young

    We have covered our shower with Redgard and now want to install white glass tile. Can we paint over this white and the tile still stick?

    • Roger

      Hi Carla,

      NO! But you can use white thinset. Done correctly the redgard will not show through. It will be just like painting it. :)

  • H Nicol

    Can redguard be used on fiberglass shower walls? Or what can be used on fiberglass shower walls, I do not want to tear the fiberglass shower out, I just want to upgrade it!

    • Roger

      Hi H,

      No, it cannot. You HAVE to tear it out. There is no way to upgrade fiberglass or acrylic walls. Sorry.

  • Scottie R Adkins

    I am going to install a redi tile shower pan my question is should I apply red guard to the shower pan before I apply the Redi Poxy epoxy adhesive when I lay the tile

    • Roger

      Hi Scottie,

      No. Tile Redi pans are already waterproof.

      • Scott Adkins

        Thanks Roger for your help pan has already been installed tiled and grouted I read extensively about this shower pan and couldn’t find that red guard was recommended pan was installed on a concrete floor in a condo Iam looking forward to a trouble free experience with this product and happy with it so far.


    Repair of 3 rows of tile at bottom of shower wall and floor. If their is any gaps after using red guard on new cement board on 3 rows of tile can you use flex seal over the gaps?

    • Roger

      Hi Ellen,

      No! Do not use flex seal in a shower, it isn’t made for that and may interact negatively with the existing redgard. Use more redgard.

  • Curtis

    I saw your site too late. Thanks for the great resource! In an effort to make a new basement shower extra waterproof, I put up 6mil vapor barrier on the studs, 1/4 inch hardiebacker on that, and then one thin coat of Redgard on that. I have not yet tiled, but just saw that this extra waterproofing could cause me problems.

    What are my best options? Am I probably fine for an infrequently used shower in a basement bathroom? Should I sand off the Redgard? Thanks in advance!

    • Roger

      Hi Curtis,

      You should be fine since it is seldomly used and you only put a thin layer of redgard on it.

  • Ryan

    Hello, we are tiling our shower. We used a recommended water resistant dry wall…have properly prepped all the walls and just before we were going to prime them, we were told to apply redgard. So we bought some…and I understand how to apply it, however I’m just worried the tile glue we have won’t stick to it. The brand we have is flextile.

    Will all these things work ok together ?

    • Roger

      Hi Ryan,

      First of all – ‘water-resisant drywall’? Which particular product (brand name). Is is densshield or purple-board (or something else)? Secondly, it depends on which particular flex tile product you have. Nearly any of the powdered adhesives (thinset or mortar) will work fine over redgard, if it’s mastic or another pre-mixed type of adhesive it can not be used over redgard. Just need a bit more info to be able to help.

  • Paul

    Hi Roger,

    I have a redi niche installed and am about to put up my CBU.

    Before applying Redgard, would you recommend taping/thinsetting the seams where the niche meets the CBU? The instructions say to fill the gap with 100% silicone, but I can’t find any info on the CBP website about applying Redgard over silicone. Do you know if it can or should be done?


    • Roger

      Hi Paul,

      Redgard will not bond to silicone. I would use tape and mud, let that cure then redgard over everything.

      • Paul

        Greatly appreciate the response. Off to tape…

  • Arnie

    Hi, I am attempting to install 3×6 Subway tiles in the bathroom and tub surround over an old mud job, the old mud job and lathe seem very solid. Those big triangular holes in the mud job I filled in with plaster. Can I just sand this down and apply Red Guard. Can I use a ceramic tile adhesive over the red guard

    • Roger

      Hi Arnie,

      Yes, since you already have it there just sand it down and apply redgard over it.

      No, you absolutely CAN NOT use tile adhesive (mastic) over the redgard – it will never fully cure. Use powdered thinset that you mix with water.

  • Mr big

    you should not be using green board to tile onto. there’s no guarantee it will not take and keep moisture, and may likely fail into a soggy mess.

  • Larry Green

    I have a existing tile shower. Can I Red Guard a ceramic tile wall. And then apply new ceramic tile with thin set??

    • Roger

      Hi Larry,
      Yes, you can, but why would you? You may be creating a hell of a lot more issues than you want. If there is water or moisture behind that existing substrate you’ll be sealing it up – that ALWAYS creates issues. It would be better and easier if you just removed what was presently there.

  • Hank

    Just installed Durock on my shower walls, Taped and muddied joints. Ready to apply RedGard For my sealer, My question is. I’m hearing stories about certain Mortar or thinset That you must use with redgard , Is this true. And i was wondering if redgard can be saved if seal tight for future jobs, Thanks

    • Roger

      Hi Hank,

      You can use any good modified thinset over redgard. The only one that has specific requirements is schluter. Redgard has an open shelf life of about one year.

  • Robin

    We are tiling our 3 shower walls. DuraRock is up and seams are all taped and have thinset on them. We have DuraRock from the shower pan all the way to the 9 foot ceiling. However, we are more than likely not tiling all the way to the ceiling. We are not sure where the tiles will stop (somewhere around 12-16 inches from ceiling), but will gauge as we get near to top and are able to use a full tile at the top and also judge by what looks pleasing to the eye. Above the tile will just be painted wall.
    My question is about the RedGard. Can we paint the whole thing with RedGard and then not tile over the Redgard? But, what then what do we cover the redgard with in the non-tiled area? Joint compound? Thinset? Paint? Primer and paint? A combination of all of these? Any recommended brands or types? My concern is having a nice flat smooth wall that looks nice when it is painted. Or, should we only RedGard where we think we are going to have tile, and then use joint compound on the DuraRock to smooth it out a bit before painting?

    • Roger

      Hi Robin,

      You can either stop the redgard at 2″ above the shower head (no water is going to get to it above that), or you can use a primer over the redgard, wall mud (joint compound), then paint.

      • Robin

        Hi Roger,
        Thanks for the quick reply. What type of Primer do you suggest to paint over the RedGard with before applying Joint compound? Thanks!

        • Roger

          Killz is the most readily available, but any drywall or paint primer will work fine.

  • Anthony Frazzini

    How thick should redgard be applied on a shower wall?

    • Roger

      Hi Anthony,

      About 35-40 mils thick, about the thickness of a credit card.

      • Aaron

        Roger, I have black mastic residue from pulling up linoleum. I’m afraid the pores of the concrete are filled in with this mastic so scraping it off is just leaving a slick surface.

        I need to tile this floor so could I Redgard the mastic residue so my tiles thin set will have a bondable surface?

        • Roger

          Hi Aaron,

          Redgard will work, but a primer made for self-leveling cement works as well, and is much less expensive. Any of them work.

  • Chad

    Can you redgard the gap between the tub flange and backer board? I was planning on taping this gap and using regard on top of the tape (a couple of coats). The gap is greater than 1/4” in some areas and is too big for caulk.

    • Roger

      Hi Chad,

      No, you’ll need to tape and mud it, then use redgard over that. If it’s too large to fill with caulk it’s too large to fill with redgard.

      Unless you meant ‘can I tape the gap and use redgard over it’, in which case the answer is yes.

      • Aaron

        Why would you need to tape that edge at the tub flange? I just skimmed over the screw heads with thinset and red guard over everything. Then set tiles 1/8” above tub shoulder. Left a nice small gap for caulk.

      • Chad

        What I meant was tape the gap with mesh tape from the bottom of the backer board down to the top part of the tub flange and regard over the mesh tape with a couple of coats. I’ve read where a lot of people fill the gap between the backer board and tub flanage with silicone and some people fill this area with thinset. My dilemma is that the gap is too big in some areas (1/4”). I thought maybe the tape and redgard coupled together could fill the gap. If my gap was around 1/8”, it would be easy to fill with silicone. I don’t have that luxury at this point! :) I’m open for suggestions!

        • Aaron

          I don’t know if it’s any help but some good quality silicone caulking should easily fill 1/4”.

          I have almost an inch gap between Saltillo and the wall where custom building products commercial silicone has stood up for almost 5 years.

          • Roger

            Yes, you can run the tape from the backer to the tub and redgard. Yes, you can also fill it with silicone – it will work, it’s just not the best solution.

            The best solution is to fill the gap with backer-rod, which is just cylindrical foam, then paint the redgard over that. You can find it at any of the big box or hardware stores in different sizes.

  • Chad

    Do backer board walls have to be dampened with a sponge before applying redgard? Also, can Silicone be used (with sufficient drying time) in corners before applying redgard?

    • Roger

      Hi Chad,

      Yes, they should be dampened. The better option is to mix redgard with 2 parts water, 1 part redgard and use that as your first coat. This seals the pores of the backer and doesn’t allow it to suck moisture from the layers of redgard as it normally would. Yes, you can use silicone first if you want.

  • Amy Sanchez

    Can I redgard a shower pan and curb if they have a PVC membrane under it?

    • Roger

      Hi Amy,

      No. It will create a damp layer (mud bed) between two waterproof layers (liner and redgard) and it will grow mold. ‘Just in case’ normally does two things: 1. Creates more problems that did not exist and 2. Declares that whomever is building the shower does not have confidence in their ability to waterproof a shower using a proven method

  • John

    First let me start by saying that I really appreciate the way you explain how to do proper tile work in just about every possible situation that is involved in the process.Very detail oriented with no bs. Awesome. Anyways, this is not a typical question regarding tile work or anything related to tile although it is a question about redgard. There’s no information on the possible application I may use it for on the bucket or online. So here it is : Will redgard stick to pvc and other hard plastics? Can redgard be painted and if so what kind of paint will stick. Mind you the application I’m inquiring about will not be exposed to any water whatsoever, but it will be exposed to the sun and temperature. This is more of a cosmetic application question as opposed to applying redgard on a tile substrate. Any information would be helpful and appreciated.

    • Roger

      Hi John,

      It will bond to pvc and most hard plastics. Paint will not bond to it in my experience. However, Killz will bond to it, and paint will bond to the Killz.