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Unread 12-28-2011, 07:38 PM   #1
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How thin can you make pre-slope in shower

I let my tile contractor start building the shower pan, but it quickly became apparent that he had no idea what he was doing, now I'm trying to finish it myself. (The pan/liner/mortar)

To start with, the house is on concrete slab, and he started with the drain about 1" above the slab. Instead of cutting the ABS pipe so the drain was flush, he filled the area with mortar, about 1" thick but screwed up and didn't really put in much/any pre-slope.

So now I have a drain/shower floor that is about 1" higher than the rest of the floor, and still no pre-slope in it. I was planning to keep building up from here since it would be a major PITA to jackhammer out the mortar he put in, cut the drain off, and install a new drain flush with slab. (This may become plan B)

At this point, I think the only downside is my curb will have to be higher so I get the 2-3" of height above the finished tile, probably about 1" higher than most since I'm starting an inch higher.

My question now is, can I put a really thin layer of motar in to get some pre-slope before the waterproof liner? I tried putting about a 1/4" bed of mortar in that was designed for shower floors, but it seems to have zero strength at this thickness. Certainly didn't stick to the previous layer of mortar at all. I was using NA2000 which is a shower base and floor mortar.

So what to do now? Should I try the 5-1 mix and try to build some pre-slope again, or break out the jackhammer and start over?
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Unread 12-28-2011, 08:06 PM   #2
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Well, I wouldn't like the extra height, myself and I'll bet it would come up pretty easy if he didn't use anything to bond it to the slab. Dealing with a high curb wouldn't be too bad if you had the whole shower done and didn't have a choice but you can prolly take it out fairly easy. Tap on it with a hammer and see if it is hollow sounding.

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Unread 12-28-2011, 09:52 PM   #3
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If you instead used one of the tiled shower systems, say Wedi or Kerdi, there is no liner with another layer of mortar on top then the tile...the base is tileable and typically only about 3/4-1" thick at the drain. With Wedi, they use foam with a special coating that the thinset sticks to and is waterproof. With Kerdi, you apply a waterproof sheet membrane to either a mortar pan you make, or a foam one you buy. The advantages of a surface membrane is that there is so little to get wet as the waterproof layer is immediately underneath the tile rather than burried deep in the structure. There are other systems than those mentioned. What you are starting is a conventional shower, which works, but there are newer, higher performance systems out there with many advantages.

Over a concrete slab, you can often taper the preslope to almost nothing if it is bonded properly. Then, the setting layer needs to be 1 to 1-1/4" thick or so on top of the liner. There's lots of info in the liberry on how to do that. When doing this on a wooden subfloor, that preslope needs to be thicker since the wood isn't as solid.
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Unread 12-29-2011, 12:05 PM   #4
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It does appear I can break out the build-up layer of mortar that was poured with a enough channeled anger and some time..

I'll probably go this route, cut the drain off with a dremel cut-off wheel, and install a new one that is flush with the concrete slab, then basically start over.
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Unread 12-29-2011, 12:44 PM   #5
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In case you don't own a Dremmel, you can buy one of these for your standard drill.....works great.
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Unread 12-29-2011, 06:31 PM   #6
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I have the same cut-off bit and it works well. The one modification I did to it was to buy a collet that slides over the shaft and is secured with a screw. This allows you to set the depth of the cut and just allow the collet to "ride" over the top of the pipe and gives you a perfect cut.

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