Lapping flange around acrylic bathtub - suggestions?

Discussion in 'Shower & Bathtub Forum & Blog' started by Fistor, Mar 19, 2008.

  1. Fistor

    Fistor Geotechnical Engineer

    Vancouver, BC
    Hi all -

    I have installed an acrylic tub, but one thing about its edges has me stumped.

    From what I understand, normally one would want to place something like galvanized metal flashing over the edge flange of the tub, tacked to the wall so that it hangs down over the flange, so that any water that might leak behind the tiles would not get behind the edge of the tub at the wall. The installation instructions that came with my tub show a cross section of the edge of the tub as simply coming straight up by an inch or so - which is what I expected.

    However, the actual edge of the tub is not like that, and instead, is "benched", between 1/4 and 1/2 in., before turning down into the tub.

    How can I place flashing over this? Should I even try? Or, should I just lap that with poly? I am worried that if I don't do anything, the little gap between the tub and the cementboard (which of course, I would silicone) may open up over time as the caulk dries, and hidden behind the tile, I wouldn't notice, and moisture would enter.

    Anyone have any suggestions, or at least, experience with this kind of (acrylic) tub edging?

    (Hopefully, my description was clear, if you have a similar acrylic tub (mine's an American Standard "Marina"), you'll know what I mean).

    Thanks for any advice,

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    No metal flashing! Either plastic sheeting or roofing felt should work fine. If you are really worried, you could use a surface membrane like Kerdi from and use a urethane adhesive to seal the tub junction (they have one called KerdiFix). They have a tile-in expansion joint system that can be used in the corners and at the tub/wall junction, so you don't need any caulk (look at Dilex). I used Kerdi and the Dilex for mine.

    Check out for tiling help.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    I cannot find that specific tub, but usually there is a "T" shaped vinyl stip available for those tubs that secures to the back side of the rim and is siliconed to the surface, with the other side of the tee going up behind the wallboard.
  4. Fistor

    Fistor Geotechnical Engineer

    Vancouver, BC
    Hey, thanks for the feedback, guys.

    Jad, your suggestion for plastic sheeting sounds fine, and should work easily... just curious why you are so adamant about no metal flashing... is it because of my particular tub situation, or would you feel the same even with a straight-sided flange of, say, a steel tub?

    HJ, here is the tub that I have:

    Anyway, I'll go with the plastic sheeting (I am not too worried about leaks, since I am really taking my time (just ask my wife), but I wanted that extra little bit of mental security, if you know what I mean).

    Thanks again!
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