# caulking between backer board and plastic shower pan



## ponch37300 (Nov 27, 2007)

I read that I need to caulk between my backer board and plastic shower pan where I left my 1/8 or so gap. Is a kitchen and bath caulk what I should use here? Do I caulk now or after I tile or both? I would think both between the CBU and pan and then again between the tile and pan. Thanks for any help with this, just trying to do everything right and the more I read/learn the more questions I have!


----------



## wrangler (Oct 9, 2008)

Yes. Before and after. The first to prevent wicking, the 2nd for basically the same reason. Anything to keep water from finding its way into the walls.


----------



## Bob Mariani (Dec 1, 2008)

Final caulking is done after. First fill the tub, so any movement is accounted for when caulking. For plastic tubs or surrounds use siliconized acrylic caulking, not pure silicone.


----------



## ponch37300 (Nov 27, 2007)

Thanks guys.


----------



## Mop in Hand (Feb 5, 2009)

Is the cbu over the flange or on top of the flange?


----------



## ponch37300 (Nov 27, 2007)

I furred out the studs even with the pan's lip and then ran the cbu over the lip as recommended from this site. I had thought about just butting the CBU up to the lip and then tile to the pan but was advised to run the CBU over the lip and down to the pan leaving an 1/8" gap.


----------



## Mop in Hand (Feb 5, 2009)

good job


----------

