How to Use a Membrane System for Tiling

  • tub_bathtub_bathroom_tile_install_installing_installation_shutterstock_12058861
  • Transcript

    LESLIE: Renovating a bathroom is a great way to update the look, function and feel of the space. Now, some gorgeous tiles can really take a blah bath and make it an outstanding room in your home.

    TOM: Good point. But the key to making sure tiles last is making sure the surfaces are waterproof. And any water getting behind those tiles can not only cause your new tile project to fall apart, it can also lead to mold and mildew and decay. Here to tell us how to make sure those tiles are watertight is Tom Silva, the general contractor on This Old House.

    Welcome, Tommy.

    TOM SILVA: Well, thank you. It’s always a pleasure to be here.

    TOM: And the name of the game is watertightness. You want to make sure that water does not get behind those tiles. I think people forget that the tiles are not the waterproof part of that installation.

    TOM SILVA: Water is the enemy.

    TOM: Yeah.

    TOM SILVA: Water is the enemy.

    LESLIE: Yes.

    TOM SILVA: Water will definitely permeate the joints of the tile. In some cases, it will go through the tile.

    LESLIE: Yeah. But you need water when you’re bathing.

    TOM: Yeah.

    LESLIE: So this – we’ve got to solve this problem.

    TOM SILVA: I’ve heard that. I’ve heard that.

    TOM: So let’s start, then, in the shower. If you’re building those tile walls, how do you make sure we keep those watertight?

    TOM SILVA: Well, you’ve got to think about the backer board that you’re using. A lot of people think if they use a cement board, that’s waterproof. Oh, it isn’t. You have to put a membrane over that, whether it’s a trowel-on type or a type that – almost like wallpapering the wall. I like that type there where you take – first, you have to do is cut the pieces to fit your size first. And they don’t have to be exact. They can have a little gap on each corner.

    But the first thing you want to do after your pieces are cut is wet the wall down with a sponge so that you can then apply a dry-set mortar over that board. You cover the entire wall with it wet. Then you take a trowel – a V-notch trowel – usually a 1/16-inch V-notched. And then you scrape the trowel over the mastic and then you have a V-notch that you can now lay the membrane on.

    Once you lay the membrane on, you have to make sure that it’s flat, so you take a flat part of the trowel and you work it in, taking all the bubbles off. Bring it in tight to the corner.

    TOM: So that V-notch trowel is key because that actually gives you the grooves in the surface to be able to get good adhesion from the membrane to the wall.

    TOM SILVA: Good adhesion. Exactly.

    TOM: Got it.

    TOM SILVA: Now, you’ve got to put your next layer on. You want to make sure that your joints are overlapped by a couple of inches and you want to make sure that the mastic or the adhesive – the dry-set mortar – goes down onto that sheet so that they glue each sheet to the sheet on that joint, along with the wall.

    Once it’s on the wall and everything’s flat and you’ve got your corners that have a little bit of a crack in it, there’s a strip that you buy that comes with the kit and you can now put your mastic into the corner. And then you put your – just like taping joint compound but you’re only going to use this spun fabric that is basically waterproof. And you put it right over the corner. Then you work all the bubbles out, make it flat and then put your floor on. Once you’ve done all that, you tape all the corners – inside corners, outside corners, whatever they have – all these little pieces of tape that will form to just about anything you want.

    TOM: So the work is getting ready for the tile. It’s not the tile part of it. It’s all …

    LESLIE: It’s always all in the prep.

    TOM SILVA: Yeah. It’s like anything. If you don’t do the right prep work, the finished product’s not going to last.

    LESLIE: Now, because there’s so many layers of these different membranes and different layers of mastic, are you allowing each sort of step of the process to dry or cure before you then put whatever adhesive over the membrane?

    TOM SILVA: Well, yeah, you want the mastic underneath the dry-set mortar – it goes on. It’s kind of loose. You’ve got to – because you’ve got to work this stuff like wallpaper.

    You put it on. You don’t have to be that fussy with it as you do with wallpaper because you’re not lining up a pattern.

    LESLIE: Wallpaper is fussy.

    TOM SILVA: Yeah. And this is not that fussy. It’s pretty user-friendly.

    You want it to be flat. You don’t want to have any air gaps under it. And you want to make sure that it’s tight. You want to let it dry overnight before you put your tile on. Actually, once it is dry, you can actually use the shower without any tile. It’s waterproof.

    LESLIE: That could be the way I get around renovating my one-bathroom house.

    TOM: There you go.

    TOM SILVA: And you will have …

    TOM: That’s not actually a bathroom unless it’s tile, right?

    TOM SILVA: If you like the orange-y walls, they’ll look great.

    TOM: Exactly.

    We’re talking to Tom Silva from TV’s This Old House.

    So, Tom, you’ve explained the right way to tile a shower or a bath. Let’s talk about what I would consider the wrong way and that is with green board. Incredibly common material. I wish it was never invented because it doesn’t seem to last at all. But we see a lot of it.

    TOM SILVA: Oh, we see a lot of it because people think it’s waterproof. It’s not waterproof. It’s water-resistant. If you’re going to use green board and you want to feel good about it, put it in the part of the bathroom that’s not the shower.

    LESLIE: Would you use it like a kitchen backsplash even, maybe?

    TOM SILVA: You could. But it’s really not any need to do it. I mean you could put it behind the stove, for example. But if you’re using the membrane that I said or just talked about, you can put that wall board in a shower. It will keep the drywall – the moisture board – from getting wet.

    TOM: Yeah. Good point. It’s water-resistant drywall. It’s not waterproof drywall.

    TOM SILVA: Right. They do make a waterproof drywall but it’s usually used on the exterior of buildings. It’s yellow in color and it’s 5/8-inch thick. Very heavy.

    TOM: Now, let’s talk about that membrane. Is that also something that you would use on a floor, say, perhaps not in a bathroom? Would you use it because it gives tile more stability in parts of the house?

    TOM SILVA: They have a product that will give the tile more stability and it actually – you trowel it right on and you go over that and it keeps the tile areas more stable. There’s less chance of cracking.

    TOM: Similar application.

    TOM SILVA: Similar applications, yeah.

    TOM: Yeah. Right. That’s great.

    Now, what about the shower pan or the bottom of the shower stall? You know, for decades upon decades, that was always a lead pan. There’s not much lead shower pans out there anymore.

    TOM SILVA: Lead, copper, even galvanized.

    TOM: Yeah.

    TOM SILVA: Galvanized would rot but when people want a mud job – true mud job – we will put in a copper pan.

    TOM: Right. Copper pan.

    TOM SILVA: And then the key is the copper pan should have a little bit of pitch to it, also, so that if the tile should ever weep or leak over, say, years later, you don’t want that water to lay in that pan. So I like to pitch the pan using shingles around the perimeter and lay the pan on that.

    But with this system that I’m talking about, they actually make a tapered-foam shower pan that basically lays on the floor. You don’t need anything under it except for the adhesive, a bigger notch trowel. You push it right in and then you go over that with the membrane to waterproof it.

    TOM: Great advice. Tom Silva from TV’s This Old House, thank you so much for stopping by The Money Pit.

    TOM SILVA: Always a pleasure.

Leave a Reply


More tips, ideas and inspiration to fuel your next home improvement, remodeling or décor project!