DIY shower remodel question

[CPA]

Redoing my master shower. I have a concrete slab floor. No basement. I will be using Schluter Kerdi liner on top of the pad. Do I need a liner under the new shower pad (which will be concrete)? I'm thinking I don't.

 

[olds]

Holmes always uses Ditra...

But:
http://www.schluter.com/media/KB-BROCHURE-Final.pdf

 

[Sluggo]

Probably not completely necessary, but if it were me I would probably put one down anyway. For the cost of the rubber liner, maybe $30, and the short amount of time, its great insurance against having to tear out the whole thing for a leak. We have used the orange stuff quite a bit with no issues, but I'm still not 100% sold on it's long term reliability, and still use a liner.

Kerdi liner is made to function with the whole system, Kerdi drain, Kerdi structural panels and everything (especially corners and vertical/horizontal joints) assembled and sealed exactly as described in their DVD, and warn that most any deviation can result in a leak.

Just my opinion.

 

[3chordcharlie]

I just did a shower with Kerdi liner (the thin orange stuff) over concrete board, and we did have a liner under the concrete pad.

Of note: I absolutely hated using the stuff. But I am far from a tiling expert.

I don't have any scientific studies to back me up, but I will say I put much more faith in the membrane than the kerdi cloth.

TBH it struck me more as a point of failure than as additional waterproofing.

 

[Greenman]

As a contractor, I always use a PVC liner in a shower pan, with the pan slopped to the drain under the membrane, it's a proven method and a proven material. Pan failures are far to expensive to risk with anything but the best material.

 

[edro]

So you are forming a sloped concrete pad on top of the concrete slab, then putting Kerdi on top of the sloped concrete pad?

 

[NutBucket]

Seems to me the whole point of the kerdi system is that you don't need any other sort of waterproofing.

On This Old House they installed it directly over a plywood subfloor in a 3rd floor bathroom.

 

[CPA]

Holmes always uses Ditra...

But:
http://www.schluter.com/media/KB-BROCHURE-Final.pdf

yeah, I have that too.

 

[CPA]

So you are forming a sloped concrete pad on top of the concrete slab, then putting Kerdi on top of the sloped concrete pad?

Yes. So, putting an additional liner between the concrete pad and the concrete foundation seems redundant. However, this is what my builder did. It did absolutely nothing in stopping leaks that ended up rotting out the wood skeleton and inviting ants.

 

[CPA]

Probably not completely necessary, but if it were me I would probably put one down anyway. For the cost of the rubber liner, maybe $30, and the short amount of time, its great insurance against having to tear out the whole thing for a leak. We have used the orange stuff quite a bit with no issues, but I'm still not 100% sold on it's long term reliability, and still use a liner.

Kerdi liner is made to function with the whole system, Kerdi drain, Kerdi structural panels and everything (especially corners and vertical/horizontal joints) assembled and sealed exactly as described in their DVD, and warn that most any deviation can result in a leak.

Just my opinion.

I have everything other than the Kerdi drain. I don't believe it's necessary.

 

[Sluggo]

Yes. So, putting an additional liner between the concrete pad and the concrete foundation seems redundant. However, this is what my builder did. It did absolutely nothing in stopping leaks that ended up rotting out the wood skeleton and inviting ants.

I've seen loads of people that don't know how to install them.

Nailing/screwing cement board through the liner to the bottom plate.
Only going one or two inches up the wall trying to save material.
Completely cut out at the drain instead of carefully cut, sealed, and bolted down.
Putting in the liner then letting other trades walk on it and drop crap all over it.

The list is endless.

 

[CPA]

I've seen loads of people that don't know how to install them.

Nailing/screwing cement board through the liner to the bottom plate.
Only going one or two inches up the wall trying to save material.
Completely cut out at the drain instead of carefully cut, sealed, and bolted down.
Putting in the liner then letting other trades walk on it and drop crap all over it.

The list is endless.

They went up about 8 inches, but didn't nail it in well enough. Plus, even 8 inches just wasn't high enough. That said, if I use Ditra/Kirdi over the sloped pad, then up the walls or over the curb, I just don't see a reason to also put a liner under the pan.