I am getting ready to install Wonderboard and tile walls above a plastic shower pan. Do you actually put the Wonderboard over the lip directly on to the top edge of the shower pan, or do you rest the board on top of the lip?

Of your flat lip has a nailing flange above that then board can set on edge. You don't want the board to terminate on top and make a seam to get past board and tile to leak Not sure haw tour pan is set up but water has to shed and not get past into wall

Signed 21 boat

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Hey Bjoytom:

Check out my picture below. You want to set the board on top of nailing flange and then fill the void between the concrete board and the shower pan with the adhesive you will be using to set your tile in (using an alkali-resistant tape will be helpful here... helps give the adhesive body to stay in place while drying). Let the adhesive dry overnight before applying the adhesive to walls and tiling.

You may also want to consider a VAPOR BARRIER (plastic sheeting.. see picture) behind the concrete board. It is absolutley required with steam shower systems, and highly recommended for regular showers.

Let me know if you have more questions here...

MARK

This is exactly what I was looking for. To follow up, should you use any specific plastic sheeting, or will roofing felt work as well?

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Originally Posted by massplumber2008

Hey Bjoytom:

Check out my picture below. You want to set the board on top of nailing flange and then fill the void between the concrete board and the shower pan with the adhesive you will be using to set your tile in (using an alkali-resistant tape will be helpful here...helps give the adhesive body to stay in place while drying). Let the adhesive dry overnight before applying the adhesive to walls and tiling.

You may also want to consider a VAPOR BARRIER (plastic sheeting behind the concrete board...not shown in picture below) behind the concrete board. It is absolutley required with steam shower systems, and highly recommended for regular showers.

Let me know if you have more questions here...

MARK

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A thick plastic sheeting (6 mil or thicker) or tar paper will work just fine. I am not familiar with roofing felt?

I agree with massplumber all though you will need to caulk between the plastic pan and bottom edge of tiles after grouting with matching caulk or it will crack

We build up framing by 1/4" inch ripped ply. That way, Wonderboard will fit nicely over the lip and down on top of the pan.