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I am prepping a 3-wall tub/shower enclosure for tile - my first time doing it. I think that I should be using silicone on the inside corners where backer meets backer.  People refer to them as "changes of plane".  Is that a good idea?

Also, if I do use silicone at those joints, do I need to tape them as well?

Thanks in advance!

ANSWER: Do not use silicone please. Nothing adheres to silicone, you will have a failure wherever the cement contacts it. The least expensive product for water proofing is called Red Guard.Roll it on...or brush. Yes tape the inside corners as well.Then apply the red least 2 coats.

Best regards

---------- FOLLOW-UP ----------

QUESTION: Hi Chris - Thanks so much for the answer.  If I do not use silicone and I do need to tape the inside corners, do I need to also use thinset on those inside corners?  Or are you saying to substitute RedGard for thinset in the inside corners? The way I understand it, the order is:

Tape and thinset ALL joints
Tape and thinset inside corners as well (changes of plane)
Apply RedGard, minimum 2 coats (following dry time instructions)
Apply thinset and tile
Apply grout


Hi Mark,
The sequence of applications you indicated are correct. If you are installing any recessed soap dishes or shampoo shelf please waterproof those areas as well.

You may notice that your trowel scrapes off the Redguard and causes it to peel... Back butter the tile in these areas to avoid peeling off the waterproofing membrane.

If you can find a matching colored grout caulking use that in the corners. There's a couple of companies out there that make them as well as your standard branded C cure and mapei.

Also consider the matching caulk at any transition...wall to floor...walk to ceiling...corner to corner etc.
They manufacture both sanded and non-sanded.

Best regards,

Flooring and Carpeting

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20+ years flooring installation ...carpet,wood,tile and vinyl. Residential and commercial. I do not sell the products , just install what ever the shop / customer has purchased. I actually love seeing the finished project completed and it gives me great satisfaction to help others acheive that goal. If I don't know the answer I will say so, and then I will recommend another expert for you. I may even research the subject and answer to the best of my ability ...including links to my sources. I wish you all success Chris


20 years as an independant contractor

H.S. diploma A.S. agriculture Mt San Antonio JR. College

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