Tile – When taping cement board do I need to tape at the walls

cement-boardmortartile

I am preparing to put down cement board for a bathroom tile install. I understand, I need to tape at the seams. Should I tape the edges where the cement board meets the drywall or the tub as well?

I was told to provide a 1/4 inch gap between each seam and the walls, so that makes me "feel" that I should do something, but what?

Also prior to putting down the cement board do I need to apply any caulk or anything to where the plywood meets the tub? Or will that be "sealed" with the mortar when applying beneath the cement board and then again when laying the tile.

Edit:
Thanks for all the responses, I am worried I may have chosen the wrong product to put BENEATH the cement board. I am using James Hardie Backer Board and the two guys at the big box who both said they do tiling on the side use below.

Steps were advised as follow:

  1. Put down tile adhesive, put down the backer board let dry.
  2. Create thinset use between backer board with tape.
  3. After dry use thin set again to lay down tiles.

Mastic advised to use

Best Answer

You don't tape the edges. Not on walls or tub. I'm not sure about a 1/4 inch gap by tub (probably would do 1/8 there) be everywhere else is fine. Nothing goes in the gap. Gap will be covered by either tile on the wall or baseboard.

Also make sure you are using the right mesh "tape". Your cement board gets same thinset as your tile .

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