Kerdi will not prevent mold. But it can minimize moisture buildup within the walls that can promote mold.

All that can get wet with Kerdi is the tile, the grout, and the thinset.

There is no tile backer board to wet and hold water.

The deckmud between the membrane and the tile is not exposed to water, so it will never wet.

What Kerdi does is prevent deep wetting. No deep wetting means faster drying. But if you have a poor grout job, or a poorly draining tiled floor, or inadequate ventilation in the shower, then mold/mildew can still form within the shower.

Alternatives? Wedi. Any topical roll/trowel on membrane (like RedGard). Some of the tile backer boards that have a water and vapor proof acrylic face.

Although Redgard will do a good job, it is NOT comparable to Kerdi. In fact, there's only ONE membrane that is, and that's Hydroment's Ultraset. All other trowel or roller applied waterproofings that I'm aware of require the use of a vapor barrier in conjunction with the waterproof membrane to be completely moisture proof. The reason is that although they're waterproof, they are NOT vaporproof. Kerdi is, as is Ultraset. It's the only one, though. Not even Laticrete's 9235 or Hydroban. Matter of fact, about a year before they came out with the Hydroban, Laticrete invited several of the local contractors in Connecticut to brainstorm on what the perfect waterproofing system would be like. My sister was one of the contractors that went to that meeting, and before she did, she called me to ask for my input. The biggest thing I asked for was a single barrier system, where no vapor barrier was required. It's the only reason I use Kerdi-- It can be used for a steam shower without having to also install a vapor barrier. Anyway, they came up with Hydroban, which still requires a vapor barrier .

That said, for normal showers, the Hydroban, I'm told, works great in conjunction with the Kerdi drain, as a topical membrane system. But again, if you're going to do a steam shower, stick with the Kerdi. For my money, it can't be beat.

we're not installing for a steam shower. is kerdi still the way to go?
can fiber glass do the same thing? TIA...

kateskouros,

I've seen some of your choices/plans for your new house in other forums, and they're very nice. Are you sure you want to consider fiberglass for your shower? Perhaps there's some other thing your contractor is talking about, but to me, fiberglass implies those moulded shower things. There's nothing wrong with them, but I had the impression that you were going for something else. My husband did our Kerdi himself, it's not that big a deal. We used it in our steam shower and in those showers that weren't steam. Don't you want tile in your shower? And even if you do do tile on the shower walls, I wouldn't do a fiberglass pan either. I've always thought that just looks like an afterthought to do that. The shower floor should be of the same caliber as the walls.

Kerdi is great stuff. But it's not the be all end all. There are plenty of showers in the world that don't have kerdi in them and survive. But it IS terrific stuff, and if you can persuade him to use it, and use it properly, you will end up with a better shower, I think.

When he's referring to fiberglass, some of the topical roll on membranes get glass mat installed at stress points, like inside corners, etc. It gets embedded into the roll on membrane.

I really don't know what to say. That's his method, and he claims it's the best, but then he admits that niches he's done in the past using that method leak? Is that his personal history, leaky niches? That's an honest question. That's more an indictment of his methods versus the materials though.

Okay, I just reread your post and see he retracted.

Personally I'm a no BS guy. And this guy is changing his story as he goes along.

I'll say that Kerdi can be "idiot proof", but it does require a certain level of worksmanship and care when it is installed. It's up to you to decide if this guy is conscientious and caring enough.

pirula, no... not using a fiberglass pan. the GC wants to use a regular shower pan and fiberglass to seal six inches up the wall (wow, big deal!). dh is wondering if he could fiberglass the whole wall...

the floor and walls will all be tiled. not using those pre fab shower units. sorry, i realize i'm not being clear. i'm getting myself all worked up because i have all these guys with their pants down with their butt cracks hanging out insisting i don't know what i'm talking about... can anyone spare a valium?

just spoke with my husband again who seems to be more reasonable... our plan is to give the GC and option: find an installer who will do the kerdi or we will hire it out ourselves. the local dealer has been very helpful and will recommend an experienced pro. that sounds like a plan... any thoughts?

did i say how much i appreciate the help? thanks again.

GCs want to do what they are familiar with and what they specialize in. So if you are using a GC who
1) doesn't want to/can't do Kerdi
2) doesn't believe in recessed nooks

Then you need to stop pushing him to do what he doesn't want to do, and just let him know that this portion of the job (the shower) you will farm out to someone else.

Frankly, what contractor doesn't do recessed nooks? Every bath remodel and model home I've seen does nooks. I did them - they are great space savers. And they are not hard to do - what's the deal, jeez, LOL.

On the other hand, if you are still having problems finding someone in your area experienced in doing Kerdi, I would consider getting off that bandwagon and keeping your eye on the prize - the whole picture. Most baths in California don't use Kerdi and they are just fine.

Oh, I see. Sorry to have confused the issue. I'm glad..

our plan is to give the GC and option: find an installer who will do the kerdi or we will hire it out ourselves. the local dealer has been very helpful and will recommend an experienced pro. that sounds like a plan... any thoughts?

Sounds like a good plan. I have read the John Bridge Tile forums extensively, and the fiberglass method does not seem to be a mainstream way of building showers. I built my own Kerdi shower several years ago, and think that it is a great system for the reasons that Mongo cited. However, I wouldn't feel comfortable having someone who is reluctant using it building my shower. Perhaps if you have an experienced Kerdi installer build your shower your GC will be impressed and jump on the Kerdi bandwagon.

dh and i believe the only reason the GC is reluctant is he can buy a cheap pan, do the install himself and save on labor while still charging us. he even told me he will be installing the pans. i really don't want a traditional install, as we remodeled all the bathrooms in our last house that way. the showers we used daily started showing mold in the grout lines. can't remember how long it took, but we weren't there that long after the renovation; maybe three years...

in the meantime i just got home from local tile store who happens to be a kerdi supplier. they are having a contractor night in a few weeks and the schluter rep for our area will be there to give a presentation and answer questions. how timely! can't wait to see what GCs response will be...

AND btw: the kerdi prices will increase as of july 1st. i think bill posted june 1, but while i was at the store they called and verified, 7/1.

the GC wants to use a regular shower pan and fiberglass to seal six inches up the wall (wow, big deal!).

Real bad idea. Fiberglass not only flexes too much, but it also expands and contracts way too much to tile over, The only way you can tile over fiberglass is if it's made specifically for tiling over, (IOW, it needs to be super thick) and you need to use a bondcoat between the thinset and glass.

I just went back and reread, and now I understand what he[s talking about. if he's talking about a fabric reinforced membrane like Laticrete 9235, that's a whole different story. When you said fiberglass, I was picturing like the body of a Vette, molded in place!