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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  • 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.

  • 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.