Do we set the tub and then put up wall?

[Jadnashua]

Kerdi has some unique properties. It is hygroscopic (water repelling) which keeps the seams from allowing water to penetrate, and you can attach it to a surface, and then tile directly to it. You use thinset on both sides. It requires that you also use their drain (it's slick) and the material on the floor, curb, and walls. Watch the video on www.schluter.com and check it out yourself.

I did a shower over Christmas for my mother with it...neat stuff.

 

[HoneySuckle]

But do I need Kerdi if there is something like Hardibacker board? Isn't Hardi similar to greenboard or durock? Are these any different?

 

[Sponsor]

 

[HoneySuckle]

Another question. Do I use Ditra on plywood for the flooring once we figure out why the floor under out linolieum is so noisy?

 

[Geniescience]

no and no.

Hardi, Durock and greenboard are all different in several ways.

If you use Hardi board, in a shower, the recommended installation is to put a plastic sheet between it and the studs. The plastic is then a "vapor barrier" preventing moisture from migrating into the studs, the wall cavity and the rest of the house. Many people have not had vapor barriers installed in their tub-shower, and have had no problems. The degree of risk is not determinable in advance. Construction methods cannot rely on indescribably perfect installation which also depends on a little dose of dumb luck to succeed. It is not a recommended practice to follow. Hardi looks and feels like it's waterproof, but it isn't. Check their web site. Hardi is not waterproof; it can let moisture migrate, it can hold water.

Why a vapor barrier? Nobody should ever rely on grout alone to block water, since grout is not waterproof itself (it can hold a lot of water) and it may be insufficiently applied in one or two places; although it can look continuous on the surface, it may cover big air spaces behind or between tiles that grab water and hold it. Pure water doesn't enable mold to grow, but soap and construction materials are food for mold. Once conditions are ripe for mold to grow, it can grow fast and give off mycotoxin gases and liquids, which might remain largely trapped behind the tiles. This explains why some showers "smell" and why powerful smells are released when showers get demolished. These mycotoxins are true excrement designed to eliminate molds' very own fecal matter; they are so powerful that they even act as chemical warfare among microorganisms, preventing other microorganisms from growing in their vicinity. That is how insulin was discovered, and that property is what makes insulin work for us. Most other molds give off excrement that hurts us; it weakens our immune system by forcing it to work very hard all the time.

The plastic sheet directs the flow of moisture down to the inside of the tub's tiling flange. This is good. Now, invisible water vapor has a direction to follow. Either it evaporates back out through the grout, or it slips down (percolates down) and collects into drips that go down into the tub or evaporate at that bottom edge where the collected water would have dripped off if it had been big enough to drop. Although a plastic sheet gets perforated when nailed to studs, this is not deemed to be a serious problem; people have not reported that studs have suffered at nail holes nor harboured mold there.

If you use Kerdi, the continuous layer of vaporproofing is now Kerdi, and not the plastic sheet. Kerdi needs support, so it goes on top of your wall surface, not underneath. Being waterproof, Kerdi ensures that the wall surface won't get wet; this explains why you can install Kerdi on top of any drywall. You don't need Hardi. You can still use Hardi, or Durock, but it is not required.

Squeaky floor:
you have a problem that Ditra may not fix. Squeaks are movement. Movement is bad. Study this first before choosing the under-tile membrane to use.

David

 

[HoneySuckle]

Thanks David. I had two people come in to discuss my bathroom woes and I got conflicting advice and ways they would handle it. Are you surprised?

First one said Hari is not as good as Durock - he will only use Durock. Kerdi is not required with Durock use. As to the squeaking floors. He advised ripping out the flooring and check the joists, maybe even adding more support there then use some type of construction glue to put plywood down and then use cement board nailed down on the plywood. Sounds like a good idea?

Second guy said two sets of sheetrock, no barrier necessary if we use something he paints on, put some good nails down on the floor and squeaking will be gone I sent him packing

 

[Jadnashua]

There are paintable waterproofing systems, but they should be used on cbu. As to which cbu is better - that is mostly a user's preference. Each one has its advantages and its deficiencies. Some are not allowed outside where it can freeze. basically, as long as it is installed properly, it doesn't matter which one.

Until you know the joist structure (the part that holds up your floor), you won't know if it is stiff enough for any tile to survive. If the planks are in good shape, you would need to screw them down enough so that they are tight to the joists. If they are all dry and split, you might want to consider replacing them. You need four things for a tiled floor to survive: a strong enough joist structure, no loose or sqeaky subflooring, strong enough subfloor, and proper installation of all materials. As already noted, on a wood floor, you MUST have some plywood down since the planks (while maybe strong enough) move too much. Tile doesn't like movement, either vertical or horizontal.

 

[Geniescience]

it goes on drywall, not Durock. So says the Company that makes it.

one more thing: according to the manufacturer, Kerdi goes on sheetrock (drywall), not on Durock cbu, not on Hardibacker cbu. Durock is not prescribed.

david

 

[Jadnashua]

You can put it on cbu, but it is harder, costs, more, and doesn't buy you anything! Now, if this is going to be a tub/shower (don't remember, didn't look), I'd consider it, since you never know about the bottom edges. They shouldn't get wet, but if anything did, that would be where problems would happen.