Waterproofing behind tile for bath surround

[mpizanie]

I noticed that the guys putting the tile up for my bath surround did not use concrete backer board. They used the blue hydro membrane but I can't tell if they used the fiberglass tape. Is it okay that they put it directly on regular drywall or should I demand they redo it with concrete backer board as the contractor told me would be used? They have not finished the tile yet. No grout has been put in yet. I showed up today to check on the job and no one was working and the contractor said he thought they would be done by now and he couldn't get them to answer the phone. Guess they took the weekend off even though they were 5 days late starting. I am in need in getting back in my house asap. Have been in temporary homes since the flood in August.

 

[Jadnashua]

As far as I'm aware, the ONLY time a drywall based product is allowed behind tile in a wet area is if it is covered with one of two sheet waterproofing membranes - Schluter's Kerdi, or Laticrete's Hydroban (not the liquid Hydroban)...there are no liquid waterproofers approved for use over drywall in a wet area. Both of those companies have had that application tested and certified to work in a wet area, if it's done per their instructions.

Mapei sells a liquid waterproofing that is sort of blue, but again, it is only allowed over cbu in a wet area. I'm not familiar with any sheet membranes that are blue, but there could be one. Regardless, when using a liquid, even on cbu, the instructions call for taping and thinsetting the seams, then once cured, covering the whole thing with 2 coats of waterproofing material. If you're using a sheet membrane, you do not need or really want to treat the seams prior to application of the membrane...it's stronger than the tape anyways, and if you had taped it, you often create a speed bump if you're not careful. That's all avoided if you do it as they tell you.

 

[Sponsor]

 

[Atomic1]

OP, you sure they're not using a denshield system? The membrane on the dens is blue, and you tape/seal the joints and screw heads with a liquid waterproofing membrane over a close weave fiberglass tape. Denshield works just fine if it is installed properly.