I am replacing my old leaking mortar shower pan. This article tells me i need to have a mortar base layer. Can I skip demolition and laying down the base layer (the old shower pan will be treated as a base layer), and just start with the shower liner and the mortar top layer?
diagram of shower pan layers

  • Why would you not replace a leaking pan? I would never try to lay more tile on top of old. After chipping the old tile out a layer of hydraulic cement may be able to seal it. Then new tile could be put down.
    – Ed Beal
    Commented Oct 20, 2016 at 7:06
  • @Ed Beal let me clarify I am considering chipping out the old tile only to lower the final floor height after that I am planning to put in a shower liner please explain the advantages of using hydraulic cement instead of a floor liner
    – joe
    Commented Oct 20, 2016 at 20:09
  • You could leave the old mortar and put a liner in but you will need something solid for the tile to stick to that is why there is a layer of mortar on top of the liner. Hydraulic cement is really good at sealing things up but I would probably want to add a new liner since the pan was leaking.
    – Ed Beal
    Commented Oct 20, 2016 at 21:52

1 Answer 1


The existing drain assembly terminates at the height of the current shower pan. Your proposal would require a drain extension to the new, higher shower pan. This would require a smaller diameter fitting, inside the old drain, in order to extend the height of the new drain. This would be practically difficult, if at all possible, because of the short lengths of pipe involved unless you're creating a "step-up" shower. By the way, such a fitting violates code by reducing the diameter of the waste pipe (even though just at the shower pan).

To avoid the above, the old shower pan would have to be excavated, at the drain, to allow the old drain assembly to be removed and a larger fitting attached; into which the new drain would be fitted.

Note: raising the height of the shower pan will result in faucet handles and shower heads being lower than they are now.

  • what i had in mind something along the lines of excavating the area around the drain and maybe chiseling off the old tiles how thick does the top mortar layer have to be
    – joe
    Commented Oct 19, 2016 at 22:50
  • I presumed chiseling off the old tiles to be a given since doing a "cold pour" (adding a new layer of mortar/concrete to an old) won't adhere to tile, let alone, well to each other unless one attaches an intervening layer of lathe (metal screen). I don't know what the minimum thickness could be as our plumber uses a min. of 1-1/2" (which, I presume, isn't an absolute min.)....the issue possibly being concerns regarding possible flex/compression at the drain site should there be any residual moisture penetration within the mortar. Maybe someone can confirm this? Commented Oct 19, 2016 at 23:17
  • i don't understand what you mean "since doing a "cold pour" (adding a new layer of mortar/concrete to an old) won't adhere to tile" in the link mentioned in the question a shower liner is placed in between the first and second layer of mortar
    – joe
    Commented Oct 19, 2016 at 23:33
  • Oh, my mistake. I was assuming there'd be a layer of mortar, to create a level surface, upon which the liner would be layed across; prior to creation of a new, sloped mortar bed. But you're correct in that many plumbers create redundant slopes (one under the liner & one over the liner) to ensure drainage of any wayward moisture. Commented Oct 19, 2016 at 23:57

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