Does preslope need to go all the way to the drain?

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Nick Evans

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I installed a 3 piece clamping drain, that is screwed flush to the subfloor.
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In my previous discussion, I was looking at the fact that my drain was not set correctly for a mud pan. I then found out about foam preslopes.
The slope has a 2% slope, and cuts to size. I installed this one.

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What I'm left with is about 3" around the drain with no preslope.
The edge of my preslope is ~5/8".
My understanding is that the preslope is just to guide the water to the drain, should it get past the pan. I feel like that is setup that way right now, where from the edge, it will slope and drain water down to the weep holes.
My question is, do I need the 3" gap between drain and edge to have something for some kind of support perspective? I'm curious if I were to have a bed over this, that small area would not be 'supported' and don't know if that's a concern at that height/distance. If I need something there to I could likely shave my excess foam (cut when sizing) to fit it, but I'm not going to invest the time if no one thinks it's necessary.
 

Jadnashua

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If your preslope doesn't go all the way to the drain's weepholes, you WILL end up with moisture pooling there, and the grout (and maybe tile, depending on the type) staying wet. Keep in mind that tile is NOT waterproof nor is the grout. Some will get beneath them and if it isn't directed all the way to the drain, you'll have issues. Plus, while you might be able to use a 'hat' to fit into that depression, most of them are designed for a deeper depression than you have. You'd never get the traditional liner to fit in there well IMHO. Now, if you wanted to change the drain to one that is designed for a surface waterproofing membrane, the hole you have is about the right size for one of those bonding flanges, but accepted industry practice would then call for extending the surface waterproofing all the way up to at least the showerhead. A bunch of companies make drains that could be used in that situation to include Schluter, Laticrete, Noble, and probably others. I'd run this buy the guys at www.johnbridge.com.
 

Nick Evans

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We'll be doing cultured marble, so I'm not certain if that has any impact on this. I get what you're saying that without a preslope all the way to the weep-holes, it would puddle. So would it work to continue the slope from the edge of the foam to the drain flange that is screwed to the subfloor? From there I can put the waterproof liner over the preslope, and clamp the 2nd piece of the drain over it. In theory it seems to me, like it would be no different than if it was a mud preslope with waterproof barrier over it at that point?
 

Jadnashua

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Does the pan's instructions call for a secondary liner? How does the actual pan connect to the drain? Usually, that connection requires a special drain, and not a traditional clamping drain. A cultured marble pan should be waterproof, and not require a liner (at least in most cases).

Usually, there's no good way to seal a conventional clamping drain to a preformed shower pan, and that's why they usually come with or specify a different type of drain.
 
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