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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Dave

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

Reply

Roger

Hi Dave,

If you are putting up fiberglass walls you don’t need redgard on any of it. The fiberglass is your waterproofing.

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Stephanie

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.

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Roger

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.

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Philip

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?

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Roger

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.

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Ted

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.

Reply

Roger

Hey Ted,

I think you’ll be fine going over the hardi with redgard.

“sandwich with lettuce and tomatoes” NICE! :D

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Persia

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. ;)

Reply

Roger

Hi Persia,

I have not abandon the site, why would you think that? :D

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.

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L

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

Reply

Roger

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.

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Aaron

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?

Reply

Roger

Hi Aaron,

You can coat it with redgard, just make sure you get the drywall mud covered REALLY well.

Reply

Hank

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.

Reply

Roger

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? :D

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Michele

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

Reply

Roger

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.

Reply

Luke

Hello,

Would painting RedGard over greenboard be sufficient for waterproofing the shower before tiling? Thanks!

Reply

Roger

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.

Reply

Dave

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

Reply

Roger

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.

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Kurt

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

Reply

Roger

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.

Reply

Mike

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.

Reply

Roger

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.

Reply

Tracy

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

Reply

Roger

Hi Tracy,

No, it doesn’t apply in that application – paint it right up onto the flashing.

Reply

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