Keep looking. It is hard enough finding a contractor that will be competent and easy to deal with once the project is underway. Luckily for you, he's already waving a huge red flag. Not your job to educate him.

It sounds like you have done enough research to know that you won't be happy with bare minimums. Yes, he could do it his way, but that isn't what you want, you want a waterproof shower.

Thank you, I'm trying to do my homework - bathroom remodel is not a cheap project to begin with, I want my money well spent - It's almost impossible to find a reputable contractor in central NJ, holmdel area, all of the 5 companies , I've interviewed so far failed the direct questions regarding waterproofing aspect of the project, some pof them belive it or not - adviseed me not to get a permits ...

The best place in my opinion to find a tile contractor is the John Bridge tile forum. The best and nicest tile contractors hang out there and will be able to answer your questions about how to proceed and maybe you will be able to find someone there to do your work.

tobik5:

I'd suggest www.homeadvisor.com. You can read customer reviews of contractors.

A bullseye for stonetech.

That means that stonetech HIT the bullseye, not that he has a bullseye on him. lol

Think of cement board in the bathroom as you do a kitchen sponge in your sink. Water doesn't cause cement board or a kitchen sponge to dissolve, decay , or fall apart. But water can pass right through both of them as they are both porous.

Cement board is great as a tile backer in a shower or tub surround. But it needs a membrane behind or in front of it.

mongo - this is what I don't understand. If water can pass through cement board, why would a membrane behind the cement board be acceptable? Wouldn't the goal be to prevent water from passing through the cement board altogether?

is it true, that :"the manufacturers of Wonderboard and Hardiebacker require a vapour barrier behind the substrate, whereas the makers of Durock and Permabase do not"?

"mongo - this is what I don't understand. If water can pass through cement board, why would a membrane behind the cement board be acceptable? Wouldn't the goal be to prevent water from passing through the cement board altogether?"

This is where it can get wacky. Understand that there is no "one size fits all" answer, but I'll address it from a couple of perspectives, and these will be grossly simplified. I can give you a specific answer for a new house that I build because I control how the house is built and I know the climate I'm building in.

But here is a mishy-mashy sort of generic explanation:

Vapor Drive. A lot of moisture moves due to differences between one environment and another environment. If your shower is hot and humid, and the wall cavity behind the shower wall is cool and dry, you can get vapor drive through the wall, with moisture vapor moving from the hot/humid shower, through the grout and cement board, and into the cool wall cavity. When the moisture vapor gets through, it can condense on the cool bare wood surfaces inside the framing bay.

Will that moisture in the wall cavity cause problems? It may or it may not. Going to extremes, if the house is in an arid desert or at a high elevation, the moisture might want to move on to an even drier environment. It doesn't accumulate or stay in the wall, so no damage occurs. If the house is an old leaky house with a poor thermal envelope, the same thing there...the basic "leakiness" of the house can promote drying.

If the moisture just stays there, and over time the process is repeated day after day, week after week? Problems can occur.

Liquid moisture movement: Grout on a shower wall can get wet. The grout can absorb moisture. Through capillary action, that liquid moisture can then move through the grout to the thinset behind the grout and tile, and through the cement board behind the thinset, and eventually end up on the back side of the cement board. Moisture movement can be enhanced by pinholes, voids, and cracks in the grout, etc, or other flaws in the wall.

Cracks in grout in wall-to-wall corners are problematic.

Again, if the house is leaky, or in an arid environment, or...etc, etc...or if the house is tight or the house is in a humid area...etc, etc...again, the moisture may or may not cause problems.

So that's a basic look at moisture vapor movement via atmospheric vapor drive and liquid moisture movement via simple capillary action. Either one may or may not cause problems.

Barriers?

Let's look at 6-mil poly behind the cement board:

It's an air barrier and a vapor barrier, so it'll stop air movement and vapor drive. So for simplicity's sake, let's discard vapor drive. We still have to look at liquid moisture via capillary action.

If liquid moisture got through the cement board to the poly, the poly stops it there. Often times, the moisture is held against the cement board. When the shower is over, the bathroom air dehumidifies and the moisture often times will dry out back into the bathroom air. It simply reverses course. If the 23 hours and 50 minutes of "drying time" each day allows the moisture that got into the wall during the 10 minutes of showering to exit the wall, then all is well.

If more moisture gets into the wall during a shower than can dry out during the drying time, then the moisture can collect and work it's way down to the bottom of the wall. If the plastic is lapped over the tub's flange and there is a path for it to escape, perhaps a weep hole, then all is well. If that bottom seam is caulked, then the moisture might hold against the back of the caulk. With the continual presence of moisture behind it, some caulks can get mushy, or discolor, or mildew out.

Topical membranes.

From your question: "Wouldn't the goal be to prevent water from passing through the cement board altogether?""

This is why I love topical membranes like Kerdi, Hydroban, RedGard, etc, in a properly constructed shower. That's exactly what they do. The only thing in a topical shower that can get wet is the grout, the tile, and the thinset. There is no deep wetting into the wall.

With so little moisture allowed into the wall during a wetting or showering cycle, it's very easy for a wall to dry out during a drying cycle.

The thing to understand is that while the goal is no water penetration into a tub or shower wall, we need to recognize that even if water gets into a wall, it may not manifest itself as a problem. It might dry back into free air before it can cause issues; mold, mildew, wood rot, etc.

Conclusion:

There are no promises when it comes to water.

A lot of moisture penetration might cause no problems at all in a leaky house or in an arid environment, because that house dries so easily.

On the flip side, a little moisture penetration repeated each day may cause a lot of problems in a tight house or in a humid environment, where drying opportunities are limited.

In either of the above environments, an adult taking a four minute shower might not cause any problems. But when a family with teenagers who take 20-minute showers move in to the same house?

You just never know.

Do understand that what I wrote is not gospel. It's just a generic and somewhat basic attempt to explain how moisture may move in to a wall, and how it may or may not move out of that same wall.

I wrote this over the course of the morning with numerous interruptions, so hopefully it's not too disjointed and it makes sense.

Personally, I'd look for a contractor who uses the old-school method of prepping a shower or tub surround ... paper, wire, scratch coat, and float with cement.

I don't like to use online referral services that contractors pay to be on. To each his own, though. Your local tile stores will have a list of local contractors whose work they are very familiar with. That might be a good place to start.

This post was edited by jellytoast on Mon, Apr 21, 14 at 13:43

I feel your pain, tobik5. when I was planning a remodel of two of my baths, I contacted 5 contractors that were highly rated on Angies List. I had an alcove tub and tile surround in each bath. None of the contractors included waterproofing in their bid. When I asked one if they would waterproof, he said they would apply a liquid product if I supplied it. But I didn't trust that they had enough knowledge to do it well.
this is in the Washington DC area. I didn't expect that contractors would think it strange that I wanted waterproofing.
I didn't waterproof my baths since I hardly ever use them. But for a shower, you need some type of waterproofing.
Keep searching for a contractor that will do what you want. good luck!

This post was edited by jules8 on Mon, Apr 21, 14 at 14:02

Thanks mongo for the detailed explanation. I was always curious about the levels of moisture in the walls that are acceptable.

This is the shower we just had done. The Kerdi membrane is truly a thing of beauty!

There was a lot of wood rot from water penetration near the window so some wood had to be replaced. That's because regular sheetrock was used and no waterproofing whatsoever. It doesn't make sense not to waterproof a shower

We are really pleased with our new shower and are confident that the waterproofing will last a long time!

Kerdi! Well there you go!

I am going to request Hydroban on the other shower (bathtub alcove) just to be perverse.

Perfict! (And thanks for the "Kudos," Mongo).....and you said it more succinctly than I ever could.....!

jerzeegirl, not perverse, educational! Be sure to report back which you like more.

tobik5, in your original post you wrote that your contractor told you:

"Either you spend a lot more money for the schluter type products or you use cement boards or hardi boards and properly seal it."

Did your contractor give any details on how he "properly seals" the cement board?

tobik5 asked:

"is it true, that :"the manufacturers of Wonderboard and Hardiebacker require a vapour barrier behind the substrate, whereas the makers of Durock and Permabase do not"?

Manufacturers will often tell you simply how to best install their product. They'll tell you that a certain framing schedule is needed to back the boards, they'll tell you haw many fasteners should be used to attach the boards.

What they often don't tell you is how to use their material within a certain system, in a shower, for example.

There are a couple of reasons. One is liability. With national, state, and local codes, building code may vary throughout the country, even from town-to-town. So often times the manufacturers will write nothing specific and only write installation generalities. Or they might wrote "consult your local building code" or "consult a knowledgeable professional".

The other is that there are so many variables in shower systems out there. A manufacturer can't reprint their literature for every permutation that can be thought up. Example, before topical membranes became common, pretty much every manufacturer wrote to "install 6-mil poly or lapped tar paper behind the cement board in a shower", because that's how showers were built.

When topical membranes became popular, people followed the 6-mil poly advice because the installation instructions said to do so. But then they installed a topical membrane on the face of the cement board too.

So things change. And with the rapid rate of change manufacturers have responded by simplifying. A lot of them will tell you just how to install their product, but not how to incorporate their product with installation options "A", "B", or "C".

Thanks for an interesting thread--
Just curious as to what your final decision was???

we need a master bath redo in FL house built in late 70's which has seen little renovation...the small shower is failing due to water intrusion...
we are planning to take out the acrylic Roman soaking tub and change to large walk-in shower...among the other elements of the remodel...

The 4 contractors we have had come bid the job (with either top recommendations from Angie's List or from local electrician we really trust) were not that great about how they would water-PROOF the shower area...
One of them would do an "old-fashioned" concrete shower prior to tiling...
and even that I am not sure about because concrete can crack...
the two others were only doing the poly sheeting behind the Hardi-board or cement board...

This house has a concrete block exterior and concrete foundation--
and shower would have two sides on the external walls, one on interior wall.
Framing niches is also an issue because only one wall will have deep enough studs...
two of the people didn't really seem to pay attention to that fact--
which makes me wonder how much preplanning they really do prior to actually gutting the space...

It can be very frustrating when you are a female who has done some research and gone through one serious bathroom remodel before where contractor DID use a waterproof membrane--liquid paint-on over the cement board--prior to tiling...which was impervious to any water source IMO--
and get patronizing comments from contractors who don't appreciate being questioned at all about their work efforts...

" ... and get patronizing comments from contractors who don't appreciate being questioned at all about their work efforts."

I rule these types out immediately. It is wise for a customer to ask questions and to ask their contractor to be specific about what they propose to do. If a contractor balks at that, I keep looking.

loves2read,

The person who wants to build you an "old-fashioned concrete shower"?

If that contractor is talking about floating mud to build your shower walls, that's an exceptional way to build a shower. A good mechanic will leave you with walls that are dead flat in plane, that are plumb, and with dead-on corners.

With the advent of lightweight tile backer boards, there are not many "mud men" left in the business.

If you can have a deck mud sloped floor with a Laticrete flanged drain set in the mud, with floated mud walls, then Hydroban the walls and floor, you'll have a very durable and watertight shower.

Yes--I know that method is kind of lost art but it would be easy to let it cure then coat with waterproofing--

we have showers in our TX house that were done w/concrete (I saw them putting in a shower even though we weren't the original owners)...just don't know if they were waterproofed after that--

but that guy drove my husband nuts--he was talking about what HE wanted to do in the bathroom -- totally screwed up the dimensions of the room when planning additional cabinetry we wanted to add--just seemed like he didn't pay attention to what we were asking for...
maybe he was just trying too hard to sell himself but he kind of scared my husband off...