Installing Redgard on Shower Walls for Tile

by Roger

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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Sam

Hi Roger,

First of all, great site! I’ve found a wealth of information on it so far.

I’ve been reading through this thread and am a little confused. If I read correctly, in a regular shower application, I shouldn’t put a plastic vapor barrier behind the backer board if I’ll be using RedGard on top (to avoid a moisture sandwich and mold). However, in a steam shower, I must put a plastic vapor barrier behind the backer board when using RedGard. Won’t a steam shower have the same problem with trapping moisture between the two barriers (plastic vapor barrier and RedGard) as a regular shower would?

Thanks in advance!
Sam

Reply

Roger

Hi Sam,

Yes, that’s correct. Liquid elastomeric membranes are not VAPOR-proof. So the manufacturers require a vapor barrier as well. You would have to ask them about the specifics of both membranes trapping moisture, I’ve never received a satisfactory answer to it – so I don’t use liquids to waterproof steam showers.

Reply

Rene

Aloha Mr. Elf,
In a walk-in shower, I have hardibacker, premixed thinset along with fiberglass mesh taped seams/corners then a wash of Redguard over. Ready to tile 2×3 subways. Now…about this whole ‘do not use premixed’ that I run across now and then. Really?!? I have just short of a 5 gallon bucket left of the premixed and mixing up stuff in an apartment is not easy.

Also, I have a horizontal stripe of clear glass tile which I need to put white behind, of which I have 4 gallons of ready-to-use white tile adhesive leftover that I planned to use.

Sigh, please tell me I can use what I’ve got in the way of thinset and adhesive.

Mahalo!
René

Reply

Roger

Hi Rene,

Yes, really. Thinset can emulsify when it is constantly subjected to water, which it will be. And it will likely never fully cure between tile and redgard. There is no such thing as ‘premixed thinset’, it is simply mastic with sand in it. I have no idea what ready-to-use white tile adhesive is, but you HAVE to use powdered thinset to bond glass tile to redgard.

Reply

Wayne Peruski

Hello again Roger,
I have a prefab shower base and on the studs is drywall. I will be covering the drywall with kerdi membrane. But first I will be installing a 14″x25″ plastic preformed niche.I’m going to cover the drywall with kerdi. The niche has a 3/4″ wide lip on it with holes for screws into the stud framing. What is the best way that you recommend sealing around the niches lip and the kerdi membrane. Do I put a bead of silicone from the drywall to the niche lip then cover it with thinset and kerdi or completely layer the kerdi in the entire niche and will it stick/bond well to the plastic. Please lead me in the right direction and a leak free shower walls.

Thanks, Wayne

Reply

Roger

Hi Wayne,

Your best option is to kerdi-fix the kerdi to the perimeter of the niche. That will bond the kerdi and give you a watertight transition.

Reply

Kelleyboralsky

Can you use redlock on green board?

Reply

Roger

Hi Kelley,

I have no idea what redlock is. If you mean redgard then no, greenboard is not a proper substrate for redgard. You need to use cement backerboard.

Reply

Dennis

Roger, I was going to used schleuter membrane for my shower and coat it with redguard. Now Schleuter wants unmodified thinset but the redguard site says to use modified polymer thinset. I am using 12 x 24 tiles with one sixteenth spacers – which is the best thinset (currently I have mapei unmodified). Thank you

Reply

Roger

Hi Dennis,

Either one will work fine. I would use modified on it.

Reply

Brooke

Hi Roger,

If I am going to use Redgard, do I mud and tape my Hardibacker seams with drywall tape or the alkali resistant tape?

Brooke

Reply

Roger

Hi Brooke,

Alkali resistant mesh tape.

Reply

Dan

Hello Roger,

Great site! Just for clarity, you recommend taping and sealing the seams with mortar before rolling on RedGard? I was going to put RedGard on, then seal the seams with tape/mortar when putting the tiles up. I guess water could still get through the mortar at the seams, and with no RedGard behind it, it could cause problems.

Reply

Roger

Hi Dan,

Yes, tape and mud, let it cure, then paint redgard. If you do the redgard first you are relying on the bridge of the redgard over the backer, if it moves and splits then you WILL have problems. Redgard gets painted over the tape and mud once it’s cured.

Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.

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Ron

So for a steam shower, you have to have both some plastic over the studs AND something like Red Gard on the cement boards?

Reply

Roger

Hi Ron,

For a steam shower you need a vapor proof barrier. With all existing liquid membranes that requires a vapor barrier behind the backer as well as the liquid over the surface.

Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.

Reply

Tauran

Hi there,
Good blog. Question. I am doing a laticrete preformed shower pan and hydroban. Do you suggest installing with a roller, or a 3/16 trowel? I figure I would paint the corners, use laticrete anti-fracture membrane and then paint them on, then either do the roller or trowel for the main surfaces. What do you think?

Second random question. do I fill the divot around the drain with pea gravel afterI screw in the drain, and then put thinset over the pea gravel (and rest of shower floor) and start tiling? Or are one of those plastic weep protectors better? :guedo:

Reply

Roger

Hi Tauran,

Of the two the roller is likely the better option. Pea gravel, then deck mud, then thinset and tile. You can use the weep hole protector if you want, they are normally too large to use with a divot, though (the ones I’ve used anyway).

Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.

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Vico

Hi Roger,
I put a first coat of RedGard over Wonderboard (and thinset on the joints) in my laundry closet yesterday. I wanted to put on a second coat today but there are many cracks and pealing all over the place. Have I put it on wrong or is it maybe a defective batch?
Thanks

Reply

Roger

Hi Vico,

I’ve never heard of that. The only thing I can think of (short of a defective batch) would be something on the backer before you installed the redgard. Did you wipe it down well and let it dry before installing your redgard?

Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.

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Ed

Thank you Rodger. Have a great holiday season!!!

Reply

Ed

Hi Rodger. TY for this great info. Quick question …….I am going to redgard my cement board (no plastic behind). My plan is to lay the top deck mud, then hang the hardibacker (1/8-1/4 inch above final deck mud) then redgard. My question is how do I fill that small gap between the final deck and the board?
1) If I don’t fill it won’t there be a chance of water sneaking in there and going from the cement board to the bare wood studs?
2) if I am to fill it do I use 100% silicone and redgard on top of it and carry the redgard a few inches onto to pan floor?
Or……
3) Would it be easier (and smarter) to lay the board before the final top deck mud (do I leave a small gap above the pan liner in this case?) and bury the board in the final deck mud then cover with redgard to “avoid” the gap mentioned above to have a solid surface for the topical regard?

Does this all sound right? THANK YOU !

Reply

Roger

Hi Ed,

I normally embed the backer in the top mud deck, leaving about 1/4″ between the liner and the bottom of the backer. Or you can hang it above the top mud deck, it just hangs there, you don’t have to fill that gap with anything, gravity takes care of the water that ‘sneaks’ up behind there. Your liner should run up the wall about 12″, so the bottom foot of your wall is waterproofed behind the backer, water isn’t going to run up your liner.

Reply

James Spurr

Hello Roger, I am building a shower stall that is roughly 9 ft long and 4 ft wide. One end is steam and the other end is a car wash. The problem is that about 5-1/2 ft of one wall and 2 feet of another wall are extremely well insulated exterior stud walls with appx 1″ of spray foam behind a layer of tarpaper behind exterior stone, with fiberglass batt in the stud spaces. There will be some plumbing with fixtures in some of the exterior wall stud spaces. I am concerned about a moisture sandwich between the interior RedGard and the exterior foam insulation.

Can you offer some advice?

Thanks in advance, Jim

Reply

Roger

Hi James,

In a steam shower application (if part of your shower is a steam shower then the entire thing needs to be built as a steam shower) you are required to have a vapor barrier behind your backer with a topical waterproofing membrane on the walls. Exterior foam insulation is not going to cause a moisture sandwich, but you need a vapor barrier back there anyway, so moot point.

Reply

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