It was recommended by the folks at Home Depot, where I bought the cement board and drywall to get this All Purpose Joint Compond.
THAT right there is just plain and simple BAD INFORMATION. Home Depot isle-walkers are known for dispensing BAD INFORMATION. All purpose joint compound IS NOT SUITABLE for use in a shower wall installation. It will melt when it gets wet.
Here's the thing Holly. You are (as others are) under the supposition that ceramic tile and grout create a waterproof condition. THEY DO NOT. Those walls are not water proof. Allow me to repeat that statement. Ceramic tile and grout on shower walls ARE NOT WATERPROOF.
Moisture will penetrate the grout and get into the substrate and behind the tiles. If joint compound is there waiting it is only a matter of time before things begin to fail.
In most cases where a bathroom wall transitions to a shower wall there is usually some joint compound existing on the joint between the cement board and the drywall. That also is a mistake but it does pass because that area of transition doesn't see as much moisture as the main field of the rest of the shower walls. In addition there is typically a shower door hung at that point which can hold the tile to the substrate.
The crack prevention mortar ALSO IS NOT WATERPROOF. Thinset tile mortar IS NOT WATERPROOF. It is not effected by moisture and will retain a bond for the life of the structure but IT IS NOT WATERPROOF.
I was under the impression that I had to put something over the cement board tape before I started to apply to mortar...was my assumption wrong?
If you had applied the tape then began the tile installation you would
have been putting the correct product over the tape but you didn't do that. That thinset will not want to bond to the joint compound either. It will for a time until more and more moisture is added to the mix on a daily basis then I would suggest you shower while wearing a hard hat and your army boots.
I suggest you buy some liquid waterproofing and paint it on an area you have filled with joint compound. Then go back the next day see how easy the waterproofing product peels away from the joint compound. It will not bond suitably.
The thing to do at this point is to get the joint compound wet. Spray it with water, let it sit for a few minutes and then scrape it off. It will come off very easily. That right there is testimony to what I am trying to tell you. But more-so it is the way to fix this fiasco.
No where in any of the industry tiling standards and recommendations does it say what you have done and what you were directed to do by Home Depot is acceptable. NO WHERE! In fact Home Depot should pay you for your time to fix their screw up. I would ***** at them and agree to take home a FREE bucket of Redgard waterproofing as a settlement.
Keep in mind that most of the experts you talk to and ask advice from at Home Depot where two weeks ago asking you if you wanted to super-size your meal at a fast food restaurant. Don't ask those guys any questions. They don't know the answers and don't think for a minute that Home Depot gives those guys any kind of specialized training because I can assure you they do not.
Okay, I'm done arguing with everyone. I am going to take my thirty-five years of experience in installing tile and quietly go away.
You have been warned.
By the way...did you want fries with your order.