We are renovating our master bathroom and were told that we should remove the green board and install blue board instead. We were also told that we did not need to install cement board over the blue board and that we could just put the tile directly onto the blue board. Can we tile directly onto the blue board with out the cement backer board?

Neither blue board or green board are currently used in a shower enclosure. Current standards are Hardiebacker board, Wonderboard, cement board. All gypsum based board must be removed and one of these products installed by glueing and screwing.

I agree with ballenger, if your going to put new tile up cement board is what should be used behind it.

You can use blue or greenboard on non wet walls if you feel so inspired and once you've reached the level of the shower head, you are no longer in a wet area. Walls surrounding soaking tubs without a shower head are not considered wet areas. You either need to use cement board with either a moisture barrier (15 lb roofing felt or 4 mil plastic sheeting) behind it, or a topical waterproofing membrane, liquid style that gets rolled on or sheet style that gets installed with thinset. You can use regular old drywall if covered with Kerdi membrane. Regular sheetrock with Kerdi membrane is probably the Rolls Royce of wet wall installations.

I agree with Bljack regarding non wet walls. My answer was a bit narrow only addressing the shower enclosure.

In wet areas, first install the Blue Board, then cement board or Mud Float ( Mud Float is for experts only) over the Blue Board. If you decide to use cement boards, then apply a layer of Premium Blend thin-set comb it with a 1/4 incnh notch trowel and locate the studs and run 2 inch screws through the cement and Blue Boards to properly secure them in place. To finish edges of tiled walls, us Qtr Rounds for they will cap off the cement boards. Good Luck

You do not NEED to replace greenboard with blue. Sounds like contractor isn't too brite. Ain in most places nowadays, it is code for bathrooms to be 100% greenboard except for shower and tubs with tile where you do need a backer and waterproofing membrane.

This post was from march.

I sure hope Tazman is long done with that project. Stick a fork in me, I'm done