Vinyl Floor/kerdi Shower System

rescraft

Doing a bath remodel and my tile guy is ready to start on the shower. He floats the walls and floors.
I know installing tile over vinyl is a no-no because of bond strength and the possible flexing of the tile over the vinyl. When looking at the Kerdi shower system, they use an expanded polystyrene floor and curb.
If tile installed over vinyl would flex, how is it that tile installed over the Kerdi floor/curb would not flex also?

PrecisionFloors

Well ain't you just a little trouble maker......

Great question

I'm curious to hear 'ol Bud's or Bill's answer to this one

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angus242

Kerdi shower base (which I believe neither Bill nor Bud use) has a density of 2.75 lb/ft3 with a 57 psi compressive strength and 59 psi shear strength.
If you can find similar statistics for vinyl flooring with underlayment, you'll have some numbers to compare to.

JazMan

There is no comparison with the two substrates. The Kerdi base and curb are fully supported with thinset. They are also very dense and when covered with tile the load of traffic is spread over a wide area. It's been tested, proved and used in thousands or maybe hundreds of thousand installations worldwide.

As for your tile setter floating the floor, I guess you're talking about the bath floor now covered with vinyl? If so, he could place deck mud over the vinyl since it is not bonded to it. Of course the vinyl and any 1/4" thick underlayment should be removed regardless.

Jaz

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Bud Cline

The issues of going over vinyl flooring aren't really with the vinyl flooring itself. Unless it's cushion vinyl. The issues are more with what's under the vinyl in the case of a wood structure. The manner in which most vinyls are installed leaves a lot of room for movement in the substrate. Since you can't see what's there and unless you were the original installer you don't necessarily know what's there or how it was installed. The more layers that get heaped atop one-another the more potential there is for movement. Then there are the perimeter-glued vinyls, won't even go there. A far as flexing...a vinyl covered floor is no more or less likely to flex than any other floor. The vinyl has nothing to do with it.

There are thinsets that will bond to vinyl so I doubt that bonding would be a serious issue.

I have used many of the Shower Kit bases and curbs and the simple answer is that that product has a suitable compressive strength. When covered with KERDI and tile the compressive forces are redistributed and improves the system even more.

angus242

My bad. I thought I remembered you (and Bill) saying you still did mud beds and Kerdi walls.

rescraft

What if you've got a 300lb homeowner and he steps into the shower with his heel or ball of his foot? Would that exceed the 57lb/sq ft loading that the Kerdi specs out at?
What if a frameless shower surround was installed, say floor to ceiling height, 1/2 thick that sits on the curb with the thin bottom profile contacting the curb? I know those can be very heavy. Do you think the loading of the glass would be sufficiently spread out over its contact area---say 8ft high by 36-40" wide?
I'm all for new materials/systems that save on labor costs. It seems that the Kerdi system is the future.

Bud Cline

What if, what if, what if?
In that case I would suggest using Noble's shower curb. The Noble curb is hollow and will fit nicely over 2X4's. This way the wall anchoring will have wood to bite into instead of only plastic.

In some cases the plastic curb-concept may have to be tossed out the window, in that case cement bricks can also be used if rigid support is required for weird walls.

I still make my own concrete floors (with KERDI) when a standard Shower Kit won't fit or when the drain is in a weird location. I use the Shwoer Kits every chance I get. They can be cut and fit or added-to but that has its limits.

There is still no "one-size-fits-all" shower floor system available, especially if you as the installer isn't allowed to be involved in the initial planning of the job. In general most customers and GC's think showers are easy and there's is nothing to them.