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    Sailorman's Avatar
    Sailorman Posts: 33, Reputation: 1
    Junior Member

    Dec 22, 2010, 08:02 AM
    To pre slope or not to pre slope... shower pan
    I am getting ready to pour a shower pan with liner. Question is, should I pre slope before the liner goes in or not? I have read 50/50 opinions, some saying to pre slope is over kill. Thanks in advance.
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
    Senior Plumbing Expert

    Dec 22, 2010, 01:21 PM

    Hi Sailorman:

    Preslope is not overkill. Preslope is the correct way to do it, period! Taking a couple hours now will pay off years down the road... I promise! Vinyl pans that don't get prepitched and collect water can eventually lead to annoying odors, mold and an efflorescence/saltpetering of the shower floor cement and the grout.

    Here is what I posted for the last guy that asked a similar on.

    You want to prepitch the membrane to begin with. Here, make sure the floor is structurally sound and then install a layer of tar paper (15 LB felt). Float a layer of a sakrete sand/mortar from 1" at the outer edges of the shower to nothing toward the drain. Let that dry overnight and then lay another layer of tar paper over that to prevent the vinyl membrane from coming into contact with the abrasive prepitched layer of sakrete.

    Install the vinyl membrane to the proper vinyl membrane shower drain and fit the corners as needed to a minimum of 6 inches above the threshold height (this is debatable). Fit the threshold and attach round patches at threshold folds/cuts. No other membrane should be needed after the vinyl membrane is installed.

    Install thick floor mud (or similar shower floor not use sakrete here), etc. A real pro would also wrap chicken wire for the threshold...tying into floor and then shaping and nailing off outside the vinyl pan only when all was dry.

    You'll also want to be sure you:

    Install a few good handfuls of gravel around the weep holes of the shower drain. These weep holes will actually do their job because you PREPITCHED THE MEMBRANE! It is critical that these holes do not get clogged with the mortar from the shower floor!

    Install tar paper to the walls of the shower running excess past the vinyl membrane.

    Install cement board to within 1/4" of the shower floor and push thinset into this space when you thinset/tape all the butt and corner joints, etc. This 1/4" space will help to prevent a WICKING effect that can cause cement boards to break down at a much increased rate. DO NOT install screws into the cement board lower than the finished height of the threshold. The threshold should be the weak spot in the system in that the shower would have water flow out of the shower via the threshold, and not any screw holes or cuts in the membrane, etc.

    Use alkali-resistant screws and tape for best result.

    Anyway, that's a quick bit of information... questions? Let me know...


    PS: You can also use a FAST SET cement for the prepitched layer if you want to move things along, but that is usually left for more experienced installers. Finally, I have presented an abbreviated version of how I do custom shower pans with vinyl. There are many others that do it different than me... give them time to pop in and see what they think, OK? Hope it helped!
    Sailorman's Avatar
    Sailorman Posts: 33, Reputation: 1
    Junior Member

    Dec 22, 2010, 09:01 PM

    Thanks Mark for the info. What are your thoughts on the Pro Slope system?
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
    Senior Plumbing Expert

    Dec 23, 2010, 04:43 AM

    I have only seen advertisements for the proslope product, but it looks pretty darn good!

    Another great system is the entire KERDI SYSTEM for custom showers. Check out the video below for more info. On that:

    In America the drain usually comes down straight through the center but kedri allows for many different drain placements... ;)


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