For a tub surround, cement board with a properly detailed barrier behind it is perfectly appropriate.

Some form of vapor barrier Is needed. Kerdi is only one brand, albeit a good one. Bare bones would require a 6mil sheet of plastic, fastened to the studs, before the cement board is installed. That's enough to keep moisture out of the wall cavities as long as there aren't any odd angles like from recessed niches, benches or knee walls. Another alternative is to install the cement board without the plastic sheet and instead roll a paint-like membrane onto the surface. This liquid-applied membrane method works well for niches, benches and attached tubs but requires some downtime to allow the 2 (two) coats of membrane to cure properly. Another system is a "sheet membrane" which is fixed to the cement board's surface without plastic sheeting underneath. Kerdi is just one of several sheet membranes which can be used.
These are examples of cement board installations. There are many other ways to build a shower though this is the least expensive method, regarding materials AND labor.
Shaughnn

The guys have to tuck the bottom of a vapor barrier inside the tub flange, so that any moisture it catches will slide down inside the tub and not into your wood (studs).

There needs to be a vapor barrier behind the cement board. It keeps moisture out of the wall cavity. Although tile and grout will shed water, they're not waterproof, especially the grout-- even if you seal it. The vapor barrier (usually either 6 mil polyethlene or 15 pound tar paper) is what keeps moisture from getting into the wall cavity, and giving mold a chance to get its start.

To Davidro1,
Kerdi is an exceptional product, and not just an internet whim. It's impermeability and versatility make it a valuable tool in an installer's bag of tricks. When I need a form-fit membrane, I usually choose Laticrete's Hydroban with fabric reinforcement, but Kerdi is effective if my schedule is tight.
I'm a certified WEDI installer and I've used quite a bit of it. I'm switching to Schluter's new Kerdi-board product instead. The permeability rating is bettter (for steam shower applications) and the product line is broader giving me a single-source warranty.
Shaughnn

is WEDI and the new Kerdi boards...just a 1/2" board like Durock is? I never new Kerdi had boards, all I read about was a roll product.

Durock is a tile backer board, but it's not waterproof. If you use Durock or one of the other cement-based boards, you still need waterproofing of some sort.

Wedi and KerdiBoard are tile backer boards, but both have a waterproof skin or surface on the face of the board. Once Wedi or KerdiBoard are installed, you just need to detail (waterproof) the seams and fastener heads. Then you tile directly on the face of the board.

Both boards come in varying thicknesses.

So my contractor should use waterproofing over the Durock? Why do they sell this stuff then?

Is 1/2" OK for KERDI/WEDI boards for walls? I guess I will get the contractors to re-bid on a job with these boards.

This is confusing, but if my contractors do not know, I guess I have no choice but to be a pain. Is there anything such as turnkey? Here, tile my bathroom.

"So my contractor should use waterproofing over the Durock?"

Not necessarily. They'll either need to put waterproofing behind the cement board; normally 6-mil poly sheeting, stapled to the studs, with the cement board then fastened to the studs over the poly...then they tile on the cement board.

or...

The can put cement board on the studs, then apply a liquid waterproofing membrane to the face of the cement board. The liquid membrane is typically HydroBan, RedGard, etc, something along those lines.

Or they can use Kerdi membrane.

Or...there are myriad variations.

What your installers have proposed, which in your original post was "...both contractors were going to use a vapor barrier and cement board" is perfectly appropriate. Their "vapor barrier" is probably 6-mil poly sheeting. Their "cement board" is...well...cement board.

It sounds to me like they are indeed offering you "turnkey".

Best, Mongo

fall, web search before posting general questions about something you just read about for the first time in this post, or any other post. There is too much in general that you can learn just by going to a corporate web site and then using a search engine for the first, simple, questions. After that (which may take a day from your busy schedule), your knowledge level is light years ahead of where it was previously, and your subsequent questions are more likely to be the kind that may require a new thread or a continuation of this thread.

hth

fall,
you got the answer to your main question you asked in post #1 :
-- yes, the guys were right about everything that you wrote they said.
-- make sure the guys know to use a plastic sheet.

Any other subsequent questions about K or other membranes might just complicate these guys' lives a whole lot. Why would you want to do that? They were on the right track already. You wouldn't want to derail them.

I am not trying to confuse them...it is just that it begged the question. I got the impression durock and vapor barriers are being outdated by improved products such as Kerdi and Kerdi Board. Why would you use Durock if Kerdi board is waterproof (and I guess better) plus it seems easier and lighter to install? The posts commment it is exceptional. But in trying to interpret the response, I guess it can be summarized that a poly barrier and cement board is OK, but other methods are better. I guess like anything, it is up to the homeowner to decide if the additional cost is warranted even though something less expensive work, may be a piece of mind thing that you have a gold plated job.

Ask your guys what other way they could do it, since you want to spend more money, and hope to get an installation that would achieve a higher standard. There are many other products and other ways of doing things, not just the one that keeps coming up on internet discussion forums. In the real world, the one you asked about is one of many, and not "the thing, the way, the one". If anyone posts to try to rebut my words, he may be a specialist who is hoping to offer minute, finegrained factoids, but for all intents and purposes, this level of granularity in details is only relevant to industry specialists.

Yes, your quest for understanding is ok, and yes the durock and vapor barrier method is (gradually) being phased out as people use more of these high tech products, and as long as no problems get reported in future decades.

A lot depends on workmanship. No matter which method. Old or new.

I hate learning about new things after the fact. I never knew the foam boards existed by Schuelter. I do recall seeing them several years ago in Home Depot, but they were made by Wonderboard (custom) I believe. I was like no way, they seemed so cheesy and too flexible. I guess the Kerdi stuff is on the same order? Are these flexible...does the thinset and tile give it is rigidity? I have a bathtub I was cement boarding around. May have to consider a redo?

I think that was called Easymat. Not sure if it is "foam" or a hardi like material. Custom even has a peel and stick underlayment...no thinset and no screws/nails. How all this stuff work, who knows.

But like anything, technology improves and standards change. Some for the better, and some are found to be flops and everyone needs to rip them out down the road because of failures.

What we do know for sure:

Is "old fashioned" mud bed jobs are the cat's a_ _. That is why those jobs are around for 100s of years.

And do not worry about having the best. IT DOES NOT MATTER. Your taste or the next owner of your house taste will HATE the style and the bathroom will be gutted again. This is WHY many have re done their kitchens...NOT because of failure, but because of the look. My 1930s mud bed jobs are perfect shape. If the next owner hates it, it will be gutted, and the cycle starts over again. As long as it is built correctly, it will last the test of time. This is why I think KERDI is an unnecessary added expense. Yeah it may be "superior" but I am sure the majority of bathrooms with plastic and durock will be gutted for STYLE and NOT FAILURE.

in supply plumbing there is pex (plastic) pipe, and there is copper. And there are other types of pipes. And there are some that have come in as the latest and newest, and later been removed from the market.

sometimes new is not better. In years from now we will all know more.

same thing applies to the subject of membranes.

steph1, since you "never knew the foam boards existed by Schuelter" I'll suggest you go web searching, before posting general questions about something you just read about for the first time in this post, or any other post. There is too much in general that you can learn just by going to a corporate web site and then using a search engine for the first, simple, questions. After that (which may take a day from your busy schedule), your knowledge level is light years ahead of where it was previously, and your subsequent questions are more likely to be the kind that may require a new thread or a continuation of this thread.

Here's a few points

Both WEDI and Kerdi-board are available in thicknesses ranging from 3/8" all the way up to 2".

Both WEDI and Kerdi-board are built on a core of extruded polystyrene foam, though Kerdi-board is a hybrid of extruded and expanded foams.

Both WEDI and Kerdi-board have a nominal insulation contribution due to their foam cores, but neither should be relied upon as the sole thermal insulation for a given plane.

WEDI's cementitious surface coatings are NOT waterproof. They are completely permeable and the product relies almost entirely on the foam core for it's impermeability rating. Because of this permeability, an epoxy coating or mortar MUST be used when installing WEDI in a steam shower environment.

Kerdi-board is skinned with Kerdi membrane and the Kerdi membrane is entirely waterproof, adding to the inherent impermeability of the foam core. Kerdi-board can be used in a steam shower environment using a high-quality dryset (unmodified thinset) mortar alone.

The WEDI catalog is limited to building panels and building kits.

Kerdi-board can be used with the entire Schluter Systems catalog of materials (over 1800 items) for a single-source warranty.

Pricing and availability for both WEDI and Kerdi-board makes them mostly inaccessible to the average DIYer. Many professionals find it nearly impossible to have a reliable source for either.

I'm manufacturer-trained with both systems and am an impartial observer. You are welcome to ask more questions and I'll be happy to answer them to the best of my ability.
Shaughnn

I hate learning about new things after the fact. I never knew the foam boards existed by Schuelter. I do recall seeing them several years ago in Home Depot, but they were made by Wonderboard (custom) I believe.

You never knew about Kerdiboard because it just became available to the public. As for what you saw, most likely it was Denshield, which is made by U.S. Gypsum-- the same people who make Durock-- and you most likely saw it at Lowes.

I remember how this thread started. It asked about Kerdi, the sheet membrane.
Why is Kerdi all over the internet?

Now internet people are asking about another product, similar in name and function.

Are Kerdi's competitors unable to create this same kind of question and answer buzz?

Davidro1,
Schluter's marketing team has nothing to do with the buzz. Left up to those bozos, they would still be trying to crack into the North American market. It's because their product line is so versatile and reliable that there are so many professionals discussing it here online when they should be spending time with their families. :)
I'm not sure what you mean by "question and answer buzz", John? If people ask questions, other people try to answer them. Schluter's not part of the equation. I know for certain that Schluter Systems has a very strict policy about not allowing any of their employees to engage in conversations about their products online. They have an excellent customer service department and that's where their field questions about their products and their applications.
Shaughnn

David, I don't know what your problem is with Schluter, and personally, I don't care. Yes, there are several other systems out there. People ask me what has worked for me as a successful shower builder. Until Hydroban came along, this was it. Even WITH the Hydroban, I'm still using a Kerdi Drain. Now if you've got other products that work best for you, that's all well and good. When you answer someone's question, give them YOUR alternative. But don't think I'm talking Schluter for any other reason than that it's a great product.

Shaughnn,
Using Google, enter this into the search field and click on Enter:
davidro1 site:ths.gardenweb.com
This will produce hundreds of results from long before "John" arrived, so please drop this idea that he and I are the same person.

Your writing style and his are similar. Your logical leaps are similar. Your suspicions and accusations are similar. You even share the same prejudices. It's an easy presumption to make, considering that Mr. Whipple is renowned for creating straw accounts to act as shills for his diatribes.
The original question was "Is Kerdi needed?" Shall we get back to that then?
Shaughnn

So, what is the consenus for a bathtub tile job....

Is Kerdi a waste, just go with poly and cement board?

Tom-- it'd be a waste. The most I'd do for a tub, is use a roll on if there were no vapor barrier behind the CBU.

Tom,
For a tub-hop, I agree with Bill. No need unless there wasn't already a vapor barrier behind the board. If I had the luxury of time though, I'd choose a liquid membrane instead.
Shaughnn

When you say tub are you assuming that it's "just" a tub.... or a tub/shower that would be used as a tub shower almost daily? Any difference in your recommendations if the walls would be wet daily from showering?

We'll be building from scratch one of these days (if our current house ever sells) and this is a question that I've been pondering. We will have a master shower that I plan on using Kerdi with because I want the peace of mind. Will have an occasionally used shower that I'm not sure what we'll use and a tub shower that will see a lot of use.

thanks

I have the same issue...for a bath tub being used daily as a stand up shower, is the poly vapor and cement board OK?
What would warrant Kerdi and why? A stand up shower?

Is a roll on better than a poly barrier? Isn't a roll on like sticking tiles to paint. Wouldn't tile adhere better to cement board than a layer of "paint?"

To rank the installation, are we saying the following:

Tar paper and cement board
6 mil poly and cement board
Cement board and roll on liquid membrane
Sheetrock and Kerdi (or other fabric)
Cement board and Kerdi (or other fabric)
Kerdi board (or WEDI)
Mud Job

And the ranking does not necessarily mean one will fail or it is bad, I guess it is how much you are gold plating it, and even to the point of overkill or unnecessary work.

For tub-shower, any of these methods are OK also.

The post by pete_p_ny said it well. (Sept 20th at 18:17).
You've said it well too, parkplaza.
You've even said that going a certain distance may be seen as overkill or unnecessary expense.
So, I don't need to add that since you already did, and I avoid putting myself into the position of being oppositional.

BUT, there is a but.

A lot depends on workmanship.
A lot.
No matter which method.
Old or new.
Low cost or high.

Personally, I wouldn't put those products into the same rank exactly as you wrote it. But I'll certainly agree that you've got the general idea, and I could live with this order (ranking) if I had to.

One of my previous remarks in this thread were to the effect that the subject of one certain sheet membrane always seems to get raised, again and again. And that people promoting or asking about other competitive products are not "seen" on internet discussion forums. Not at all. Not one bit.

Discussing your ranking might be a sterile discussion: i.e. little or no real change or result will come of it. Thatis because you have definitely got the right idea, in that ranking. However, I'm sure it would not be a surprise to find out that some (or many) people) will vouch for the many liquid membranes there are out there. They are great. Think of rubber, not a thin and brittle coat of paint. Believe me when I tell you that they are good. In the real world, these products do get manufactured and delivered, bought and sold, installed and warranteed. So just be aware that all of us often talk about one product only. It's only one out of many good products. They are all good. None are bad.

HTH
.

gbsim-- That recommendation is specifically for a tub/shower combo that will be used daily. If it was "just a tub", all you'd need is sheetrock, nevermind waterproofing! :-)

Thanks Bill.

So is it the meeting of the walls with the drain pan at the floorline that makes the shower so much trickier and thereby merits Kerdi if you want a bulletproof shower that will be there in 30 years?

Gbsim,
The presence of a shower head, and the high probability of water on the walls, which make it a shower. Whether a tub-shower or a full shower with pan, the wall treatments are the same.
Shaughnn

Yeah-- what he said! :-)

My tub is being used as a shower being all I have is a tub (no stand alone shower). So to the original question...are my contractors wrong....it should have waterproofing in the form of Kerdi products (fabric or board), WEDI products, or a paint on with roller version?

yes. Either a vapor barrier behind the cement board, or waterproofing over the top of it.

I have been blessed to live in a beautiful island state where the ocean is a key part of our daily lives. But all of you, regardless of address, has a responsibility to the planet. Whether you believe Earth came to us in a big bang or was given to us by a loving creator, it is our choices that will shape it for future generations.

1. The fact that Styrofoam is lightweight and floats, means that over time a great deal of Styrofoam has accumulated along coasts and waterways. It is now considered the main component of marine debris. Styrofoam is manufactured by using HFCs, or hydrofluorocarbons, which have negative impacts on the ozone layer. Styrene is also known to be toxic to the reproductive system. The brominated flame retardants that are used on Styrofoam are also causing concern, and research shows that these chemicals have negative environmental and health effects. Combined with the fact that all the scraps and waste of this Kerdi-Board material will be sitting in landfills for hundreds of years because it takes so long to biodegrade.

2. The laminate (waterproofing) that Kerdi is made from is polyethylene. The same plastic that the grocery bags are made out of. Which are now outlawed in Kauai and Maui counties. There are many ways plastic is bad for our environment. From its manufacture to its disposal, polyethylene emits toxic compounds. During the manufacturing process dioxin and other persistent pollutants are emitted into the air, water and land, which present both acute and chronic health hazards. During use, polyethylene products leach toxic additives. When polyethylene reaches the end of its useful life, it can be either landfilled, where it leaches toxic additives or incinerated, again emitting dioxin. The world's "great garbage patch" can be found floating between Hawaii and San Francisco. This garbage patch is estimated to be twice the size of Texas and thousands of pounds of our discarded trash, mostly plastics.

These materials have no business being pumped into our economy and homes. Large corporations make up lies about the impact the production of such materials has on our earth and it's inhabitants. I will have no part in increasing the use of these materials. Not when mortar methods are and have been available to us for generations. It is only laziness that breeds the use of these products. They, in no way, lead to a better finished product.

I am moving my shower. The new location has drywall(sheet rock) on the studs. Should I remove the drywall or just put the polyfilm on top of it?

Do you just go to the bottom of the stud with the polyfile and end or leave some extra?

Johndrew,

You don't want to bury drywall behind another type of backer board in a shower.

A couple of choices are to:

1) Leave the drywall and use Kerdi membrane over the drywall. Drywall is an approved substrate for Kerdi membrane.

2) Pull the drywall and toss it. Then use cement board over the studs, use a liquid membrane over the cement board (Hydroban, RedGard, a liquid membrane like that).

3) The least expensive would be 6-mil sheet poly over the studs, then cement board over the poly, and tile over that. If you use sheet poly, let the bottom edge of the sheet poly drape over the flange of the shower base, or over the shower pan membrane.

There are other typed of lightweight tile backer boards out there, some with foam cores, some with gypsum-based cores. I don't use them, a personal choice.

bobvilas,
thanks for mentioning the environmental considerations. I try to avoid plastics when fixing the house, when possible.
Laura

If you don't use the plastic in your house, it's just going to get thrown in the trash. So save the earth, use plastic!

Hi everyone, I know this is an old thread-but I am need help to choose the right way to REDONE our shower ( with a Rain SHower on the ceiling). Original contractor was using a copper pan but he did not put a weeping holes ( plumber stated it was the tile's responsibility) and they DID NOT waterproof the shower after installing Durock, just tile after that. In 2 1/2 year finally water is sipping through the BENCH that is not waterproof. Also the copper pan did not installed under the Bench. So now the contractor will completely gut out the shower, I prefer them taking out the Copper pan- now should we continue using the cement board with the Redgrand membrane, KERDI or WEDI. We heard issue using WEDI in California, but we live in Massachusetts. If using either WEDI or KERDI are expensive, but if gives us a better and last longer shower, we just have to eat the cost. Thanks Yani