I understand that the layers under bathroom tile go (from bottom to top): Kerdi membrane Chicken wire Hardboard Tile
What is the purpose of the chicken wire?
Also, I know that Thinset is used to hold the tile to the hardboard. But where else is Thinset (or other compounds) used in between the lower layers?
You're using the membrane as a cheap replacement for a copper pan? It's not needed in a normal bathroom floor application. I'd be leery of using something like that in a shower. It seems to be advertised for "constant steam" applications, like for walls in steam rooms, to reduce the migration of moisture through the wall.
Chicken wire might serve as structure in a sandmix bed, like rebars in concrete, though I've never heard of it being used. For bath floors I normally screw concrete board to plywood subfloor and use thinset on top of that.
I know a lot of people use the hardboard. I'm hesitant to trust it because it seems to be some kind of glue- based composite. Like using flakeboard for sheathing: It might work fine, but what if the glue breaks down in 20 years? There's nothing else holding it together.
Copper pan? You mean inside a shower, right? (I've always heard 'lead pan', not copper). Anyway, this is just regular floor tile outside the shower, but still prone to getting wet sometimes.
Re concrete board: I thought that was the same has hardboard.
From what I could make of it, the chicken wire is intended as a sort of cushion to keep the tile from cracking under uneven pressure. But I don't deal with this stuff.
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Schlueter system, all the way. makes a stable, waterproof tile floor with minimal thicknes penalty and weight.
| Anyway, this is just regular floor tile | outside the shower, but still prone to getting wet sometimes. |
There's no reason for a vapor barrier under that. But if you have large tiles there is reason to make sure the subfloor is strong and stable -- that it doesn't flex enough to possibly cause cracking tiles down the road.
| Re concrete board: I thought that was the same has hardboard. |
It may depend on where you live. What's available to me are two things. One is called something like HardiBacker. It's a composite fiber board. The other is actually a sheet of concrete, usually made lighter by the addition of stryrofoam pellets, and reinforced with fiberglass mesh. With the concrete board and thinset you end up with something that's like a solid sheet of mortar. The backer board may be fine. I just avoid it because it's a fairly new product and I don't want to trust the long term integrity of whatever bonding agent they're using.
| From what I could make of it, the chicken wire is intended as a sort | of cushion to keep the tile from cracking under uneven pressure. But I | don't deal with this stuff. |
I've never heard of that. It wouldn't make sense with thinset. There isn't enough depth. The only way it might make sense that I can think of is "for good measure" when pouring a bed of sandmix. That's what you might do for something like brittle marble tile, but not normally for floor tile.
I don't know what that chicken wire is all about.
And, from what I understand, Kerdi is primarily used on walls to prevent humidity from accumulating inside the walls with the result that mold grows in there.
For a wall, Kerdi serves much the same purpose as Red Gard; it's a moisture barrier to prevent humidity accumulating in the walls.
For floors, I think you want to use a different Schluter product called "Ditra".
Ditra is a plastic mat.
You see, wood is a natural material that swells and shrinks with changes in it's moisture content. Ceramic tile and the thin sets used to set ceramic tile simply don't have the elasticity to accomodate that movement in the substrate. So, it's never a good idea to set ceramic tile directly over wood of any kind, including plywood.
This is why Mayayana says he screws a dimensionally stable tile backer board down to the wood floor first, and then tiles over that dimensionally stable tile backer. The effect is exactly the same as standing on the fault line the day before the quake. There can be tremendous stresses in the rock a mile below your feet, but if the ground under your feet isn't moving, then you're completely unaware of any tension or compression in the ground down there.
So, if you were a grout line, you'd have no reason to crack.
I exagerate when I say there can be tremendous stress between the wood bathroom underlayment and the dimensionally stable tile backer board. Wood used in construction is relatively soft and compresses easily. Also, the movement of the wood is small and the screws will bend a little too.
The important thing to remember is that the tile gets set on a dimensionally stable tile backer board like Hardibacker board, Wonderboard, Durarock, Aquaboard, DenShield, etc. so that there's no tensile or compressive forces put on the tiling because of swelling or shrinking of the wood below.
Schluter Ditra accomplishes the same thing without using a dimensionally stable tile backer board. It's a plastic mat that allows movement of the wood below the mat without causing stress in the tiling above the mat.
And, because Ditra is a PLASTIC mat, it prevents to accumulation of humidity in the floor just like Kerdi does in the walls.
If I were you, I would use Ditra under your floor tiles, Red Gard or Kerdi under your wall tiles, and leave the chicken wire out.
To keep out the chickens.
I used it and I have no chickens in my bathroom.
Agreed. Don't try to complicate it by mixing different incompatible processes and using materials that are not intended to be used as you are planning. Go the entire Schluter system and you cannot go wrong. It may cost a little more but will give you an iron clad installation. Check the Schluter.com website for detailed instructions on using their materials. Shop around as prices do vary with the big box stores being the most expensive and with a limited selection of components. Large tile shops/warehouses can have the lowest prices and the best selection.
Checking back: I just spoke to someone at Thinset (asking about max thickness) and described the general layout without mentioning the chickenwire. The lowest layer is oak floorboards, so that may have something to do with this. Granted, the guy at their help desk was not an installer, but he thought that oak may present a problem in dimensional stability. But he also thought that Hardibacker and concrete board are the same, which in this case, is not true.
If there is a problem with dimensional stability of oak, it should not be of much consequence within the small 1 foot by 2.5 feet rectangle that I'm working with. But I would think that any dimensional problems would relate to ply or other types of wood as well. Perhaps that's where the chickenwire was supposed to come into play.
I ended up using hardibacker for spacing, under concrete board, then the large slate tile.
L
I think you need to forget about the chicken wire. :)
You're only tiling 1' x 2.5'? That's a very small space. Oak boards would be less stable than plywood, which has plies alternating in opposite directions for stability. Also, if the oak ever gets wet it might swell up. If it were me I'd either take up the oak or at least go over it first with something like 1/2" plywood. But if it's good and flat you're probably fine. As long as you seal around the edges (in case there's ever a flood) you'll probably never have to worry about it.
Chicken wire is used as a reinforcement in a custom mud bed shower pan. Expanded metal lath, or metal hardware cloth would be better choices if you can get them.
If you're just tiling a bathroom floor, you can skip the Kerdi and chicken wire. Just install the backerboard, then tile directly over that.
If you're building a custom shower pan with a mud bed, you would normally install a layer of roofing felt or rosin paper on the subfloor. This acts as an isolation membrane, and prevents the subfloor from sucking the moisture out of the mortar before it cures.
Then you would install your reinforcing wire, and build up your mud bed. Hardibacker board is used on the walls.
Then you can install your Kerdi waterproofing membrane on the shower pan and up the walls.
Finally, you can install your tile, and grout it once the thinset has cured.
Of course, this is just a basic overview. There are a lot of details you should research first. I recommend you visit the John Bridge tile forum and study Kerdi shower pan installations:
You can also see how I handled the different situations in our two bathrooms at:
Take care,
Anthony Watson
| Then you can install your Kerdi waterproofing membrane on the shower pan | and up the walls. |
I'm curious why you'd recommend that. This forum is the first I've heard of plastic backer films. I've used concrete board for many years. Companies like Durock have never recommended moisture barrier. I put plastic sheet behind the lower section of concrete board on walls, in case there's ever a long, slow leak, but I'm careful not to seal the board entirely. The idea is that water shouldn't be getting through in the first place. If it does, sometime down the road, the concrete board can diffuse it without breaking down.
By putting a sheet of plastic between tile and board, or between tile and sandmix base, you're breaking the continuity of the mortar, for no apparent reason that I can see. If the tile were not, in itself, waterproof there would be little point in going to the trouble of using it.
Are there some kind of studies somewhere -- not paid for by the plastic membrane companies -- showing that the polyethylene layer is somehow an improvement?
I could see the possible logic of using such a membrane in places like low-end condo conversions, to float a floor on the subfloor without needing some kind of mortar base or board, though even that seems hokey to me. I can't see the logic of what you're describing.
Before Kerdi was available, the traditional way to make a waterproof shower pan was to have a custom copper pan manufactured, or to use a vinyl pan liner embedded in the mortar bed. In those cases, the tile backer board usually overlapped the shower pan, so any water that found it's way behind the tile "should" eventually work it's way down to where it would drip inside the pan liner. (I believe you're supposed to keep the bottom of the backerboard up off the pan so it doesn't wick moisture up into the wall) Of course, it's always better to keep the water out of the wall in the first place.
Kerdi is applied to the mortar bed AFTER the pan is built-up. It is installed directly under the tile. In this case, the kerdi waterproofer laps up the walls, and the manufacturer recommends it extend up above the water source (shower head or tub spout, whichever is highest). It makes sense as you wouldn't want any water getting behind the kerdi membrane and into the structure. Basically the entire shower area becomes a unified waterproof barrier.
Tile is waterproof. Grout is not.
Also, Kerdi isn't just a sheet of plastic. It's some kind of fabric material and you use regular thinset to install it.
I am not aware of any studies, but I seem to recall several topics on the John Bridge forum talking about moisture problems in traditional vinyl lined mud beds. It has been about 10 years since I really researched tile work, but I believe the moisture soaks through the grout and into the mortar above the liner. Mold, mildew, and probably other problems. You might search the tile forum if you need details.
I used Kerdi on our entire master bathroom, even the flat areas of the floor that didn't need to be waterproofed. Zero problems in the last 10 years. Compared to all the other costs of building a bathroom, the cost of Kerdi was insignificant. Certainly cheaper than a copper pan.
Anthony Watson
While it still has seams, epoxy grout is far superior to sand grout.
I used a one piece Swanstone base for my shower and I'm going to do the same in the other bathroom soon too. Tile on the walls and floor.
| I used Kerdi on our entire master bathroom, even the flat areas of the | floor that didn't need to be waterproofed. Zero problems in the last 10 | years. Compared to all the other costs of building a bathroom, the cost | of Kerdi was insignificant. Certainly cheaper than a copper pan. | It's good to know that it's held up. I'd be wary of the interrupt it's causing between the two layers of thinset. They claim that hairs on one side, and insets on the other, solve that problem. Maybe so. I still find it hard to justify using it, though. In a copper pan it makes no sense, and a shower should not be built without a copper pan.
On a wall inside a shower, using concrete board, I could see how it might seem to make sense, but water simply doesn't get behind the concrete board normally. Grout *is* waterproof. If it were not then people would have to rebuild showers every couple of years. The only problems I normally see are where there's a gap between a tub and wall, and people don't keep it caulked.
On a wall or floor outside the shower I can't see any possible justification. As you say, it's creating a "unified water barrier". But that would only be relevant in the case of something like a tub overflow. In that case, the water will not be going through the tile floor, anyway, in all likelihood. It will go down through the gap around a radiator pipe, perhaps, or under the door and through the floor in the hall. It would never be held in the bathroom long enough to test the resistance of the tile floor.
I have never used a copper pan, so I can't really say much about them. I suppose they would work fine in a traditional square or rectangular shower, but irregular shapes might be tricky. Copper pans aren't really DIY friendly either. Kerdi is.
Our master shower is 6'x6'. It would have been very expensive to have a copper pan made for that size of shower.
A quick Google search ("is grout waterproof") shows numerous sites that disagree.
If grout and tile were waterproof, there would be no need for a shower pan or waterproofing membrane beneath the tile.
Walls are less likely to have leaks because the water mostly just splashes on and runs off. Floors are a different matter where water can stand and soak in.
For the most part, I agree with this. In my case, I had extra Kerdi leftover with no other use, so I went ahead and waterproofed the entire bathroom floor. If there's a major spill or the bathroom sink develops a leak, it's just an extra layer of protection.
Also, we have a "curbless" shower, so in effect the entire bathroom becomes part of the shower pan. I had to cover most of the floor anyway, so an extra three feet was insignificant. I had it, why not use it.
I was very skeptical of Kerdi when we built our house, since I had never seen it used before. Now that I've used it, I can't imagine doing a shower any other way. It's waterproof, easy to install, and relatively inexpensive.
Anthony Watson
replying to HerHusband, Red rock wrote: They are using chicken wire instead of expanded metal and floating it . If you do this you don't need hardy backer or Schluter system. Its stronger but more work. grout is not perfectly water proof. That's why you should use sealer every couple years.
replying to HerHusband, Red rock wrote: They are using chicken wire instead of expanded metal and floating it . If you do this you don't need hardy backer or Schluter system. Its stronger but more work. grout is not perfectly water proof. That's why you should use sealer every couple years.
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