Steam shower + glass mosaic tile on floor + Kerdi + shower bench = confusion

[enovikoff]

I'm building a 4x6 steam shower with a 1x1 glass tile mosaic floor. The walls are 6x6 and 4x4 porcelain tile with a stone mosaic border (2x12 sections) across the middle of the wall.

After reading the forum postings on glass tile and Kerdi, I propose to use unmodified thinset under the porcelain tile, and modified thinset under the glass mosaic and the stone border. Does this make sense? Will the unmodified thinset be adequate to hold the porcelain tiles to the ceiling (using John's masking tape technique)? Or should I use some sort of epoxy-based thinset if such a thing exists? How about the grout: does anyone recommend epoxy grout for glass tile?

With regards to the shower bench, I like John's concrete block method, but am not averse to building it out of wood either. In the case of the wood/plywood bench, the Kerdi would go over some hardibacker screwed to 1 1/8" plywood (at least on the seat). However, with the concrete block method, where does the Kerdi go? Over the blocks, or on top of the shower floor with the blocks resting on the Kerdi? (That seems risky, might damage the Kerdi...) Are there weight issues with John's concrete block technique? I've reinforced the floor under the shower, but...

Thanks for the advice, in advance!

-Eric

[muskymike]

Hi Eric, you can use the unmod like you said in the areas of the porcelain, and the mod with the glass. As far as the ceiling , I just back butter the piece with the notch of the trowel, and flat trowel the kerdi they should stick just fine. The block bench will have to be wrapped in kerdi too. The weight shouldn't be an issue.

[cx]

What Mike said.

There is not problem building a wood-framed bench and covering it with Kerdi if you'd rather do that.

The biggest feature of the "monument" bench is that it's made entirely of water-impervious materials and can be constructed inside the pan of a standard shower without worrying about trying to seal it. That feature is of little value if you plan to cover it with Kerdi anyway.

You could, of course, build a Kerdi shower and then construct the monument bench inside it, but then you lose one of the biggest features of Kerdi construction, which is that no water ever goes deeper than the back of the tile.

Build your bench whichever way is most convenient for you, then cover it with Kerdi, would be my advice.

My opinion; worth price charged.

[GINA JOSKE]

Hi Eric,

In Reference To The Bench, You Might Want To Check Out The Better Bench, No Water Proofing Needed. And Is Ideal In A Steam Shower Application.

[enovikoff]

I've checked out the Better Bench - it's not for me. Because of the fasteners, it's one potential source of leaks in a shower which will only have penetrations for water pipes since it will be a Kerdi-shower. But more importantly, I have purchased some kewlio sea-blue glass mosaic tile that I want to have cascading down over the seat onto the floor, which means I need a "monument"-style bench rather than one with a space under it.

[John Bridge]

Eric,

You plan to install the glass mosaics direct to the mud seat, right? No Kerdi on the seat.

BTW, I use the Better Bench from time to time. It's a great product. I screw it in over the Kerdi and then tile it in, too. It's going nowhere.

[enovikoff]

John,
I'm still waffling about the seat (structural modifications to the house to stiffen the floors are taking longer than I expected, so I have plenty of time to waffle!) In either case, I'd put the 3/4" glass tile directly on the kerdi with modified thinset and a long drying time. The kerdi-covered wooden bench is looking good from a simplicity standpoint. If I build a monument bench, which I like the idea of because it doesn't flex, I'd put the kerdi over it, since having the monument rest on the kerdi seems a little strange and dangerous: I might puncture the kerdi or something, and I'd potentially get the mildew/mold problems you talk about in your book with respect to mudded shower pans over traditional waterproofing. Does this make sense?
-eric