Question about cork as an insulator in a shower [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-20-2008, 01:21 PM
Generally my company will advise a customer to use some sort of insulation over their slab when installing an electric radiant heat system - cork being the usual recommendation. In the event of a shower installation, if the cork was installed on top of the poly material, would it be possible that the water would soak through pinholes in the grout, through the thinset cement and penetrate the cork? If this were the case, would it be possible that the wet cork would stain the grout an orange/brown color?

I really appreciate the information. This is a great forum, and has been a great source of information for me! Thank you all in advance.


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02-20-2008, 03:24 PM
I wouldn't want anything organic on top of the liner. It'll just be food for mold. Besides, are you intending to heat the shower floor?

02-20-2008, 03:36 PM
I'm about 100% sure that if you were to look at that cork now it is all wet. I can't see how it wouldn't be.

02-21-2008, 10:33 AM
Yes, we are heating a shower floor. I had recommended using cork as an insulator directly on top of the slab, but when they installed the system they ended up putting the cork over the water barrier. They are now having issues with the grout staining. I was trying to figure out if the cork got wet would the grout wick the stained water resulting in the discoloration of the grout? I really appreciate your help everyone.


02-21-2008, 10:59 AM
Wow! I'm not an expert but I do know that I wouldn't want anything in the wet environment of a shower pan made out of wood. And I'm confused, the cork is recommended for underneath the heating elements. Did they put the heating elements inside the shower pan as well, on top of the cork? Ouch! Or did the installer mess up further and install the heating elements, the pan liner, then the cork?

I also don't understand why anyone would want a heated shower floor. If you want the floor warm, turn the shower water on full hot and leave it like that for about 30s and voila, heated shower floor.

To answer your question Seth, I think it would be quite easy for something like cork in the shower pan to discolor the grout. Not to mention whatever they used to bond the cork to the pan liner, and whatever residue might come off the heating elements, assuming they were also located in the pan.

I'd say it's time to rip it up and start over, IMHO.

02-25-2008, 09:25 AM

They've got the pan liner, a layer of thinset, the cork with heating system on top, and then the thinset beneath the tile. I figured we were getting to the "tear it up and start over" point.

I really appreciate all of your input everybody! Thanks a ton!