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 9235 and Hydroban. I will refer to all the membranes as Redgard for the purposes of this post, but they all work 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.
It 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.
You can also install Redgard directly onto drywall if that’s what you choose to do. While this is not recommended procedure, it can be done. You must first rough up any paint that may be on the drywall. There has to be a surface the membrane can stick to.
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 9235, 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.
Most of the product specifications for these materials state two coats to be sufficient, and it probably is. I always 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, 9235, 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.
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Hi Roger,
I have almost have walls ready I have 1/2′ hardy tub shower area and 4′ high around rest of bathroom I am ussing redguard .on outside wall plumbing is all way cross if I use all hardy on oust side wall (also has window small) i am thinking I want to tile that whole wall insolation at tub i pulled vaper barrior off because redgaurd should i do that on that whole wall and red gaurd it ?then next question tile floor will meet 3/4″x 5″hand scraped prefinished hardwood what if anything should do to make it right highttile to wood and and waht to marry the two at thresh hole at door way?
Thanks so much,
Carol dawson
Hi Carol,
Yes, you should remove, or at least cut slits into, the barrier on the outside wall and redgard everything.
You’ll need to build up the substrate / thinset to the proper height to be level with your wood. Schluter makes several transition strips that can make that transition. You can also just leave a gap there and silicone it – DO NOT grout it. It’ll crack.
thank you for your quick reply you have been wonderfull
Carol dawson
Can I use the redgard directly on hardiboard? I have an open shower and I may get a little
water on the bathroom floor, I thought I might apply redgard to the hardiboard on floor before I tile….??
Hey Vic,
Yup, no problem with that at all.
Hey Roger,
Getting ready to install the floor. Should I complete it, with grouting, before starting the walls?
You can if you want to. It really doesn’t make any difference at all. If you do the floor first and complete it that does give you a more solid surface to work over as you are doing the walls.
Would it be a problem to use redguard on the studs facing the tub enclosure as an added barrier against any leakage beyond the membrane? I know this harkens to the “moisture sandwich” effect, but shouldn’t the moisture should be able to evaporate through wicking action in the 16 or so inches between the studs?
Hi Matthew,
If you need an ‘added’ barrier, then your initial barrier isn’t doing the job, eh? You can do that if you want – it won’t hurt anything, but no real need to.
The problem with using the redgard rather than a barrier (I know that isn’t what you asked, just putting it here for others that may think of doing it) is that yes, the moisture can evaporate into the wall cavity, but it will also condensate there on the sides of the studs.
Roger,
hardibacker installed, but all screws are not exactly flush, and can’t get them to screw any farther. Will this affect the tiling process? I’m going to Redguard before tiling.
Thanks,
MP
Roger.
Amendment to previous post. Hardibacker installed, but some of the hardibacker screws didn’t countersink. When placing tile over them, they tetter a bit, from the higher than board screwhead. Will the 2 coats of redguard and the thinset compensate for this at all, or do I need to go back and countersink all the holes? Could it be that my drill hasn’t enough torque?
Thanks,
MP
Hey Mike,
As long as they don’t stick up more than 1/16″ or so the thinset will compensate for it. If you used the correct screws then it probably is either your drill (if it stops or slows toward the end) or the bit (if it is stripping the screws).
Can you use Redguard behind glass tile? Will the red color show through the thinset behind the tile? If doing glass tile (in a shower), what would you recommend for the waterproofing layer?
Hey Boogamite,
All three of your questions have the same answer – it depends on the glass. Every manufacturer has different accepted or recommended methods with their product – contact them and they can answer all three for you.
In general: yes, you can use redgard behind glass. Yes, the red color will show through unless you use white thinset with full coverage. And I always talk to the manufacturer. I prefer kerdi, but make sure that’s acceptable to them before I do it.
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