[look 171]

Hydrophilic ?

Widebody,

Its ok to screw through the water barrier on the vertical surface but not on the flats areas like the step or the pan where water can seep through. You tile is water proof, but not the grout joints. There is a lot of water in the back of the tile through the grout joints. I have seen water gushing down the back of a stucco wall during a light rain, because people do not over lap the builder's paper. Instead, they get lazy, or simple do not understand how thing work, and lap it the other way when they patch. Your step may not leak, but why take a chance. I would not install it that way if that was my client's home. I have to make sure I do not get call backs and no law suite in the future because of bad installation methods. Just think what Mike Holmes would say?

I am telling you buddy, that's a mistake waiting to happen.

If you want to save a few bucks, mop or fine someone like Trek and use the rubber membrane then float the pan. You can then use build's felt and Hardy Backer over the vertical surface (We flow everything). when you float the pan, the guys should mop it up about 12" onto the wall. overlapping 12" on the bottom will keep water out for sure. Make sure you fill the pan with a few inches of water and wait 24 hours. Re-measure to make sure there are no leaks before you flow. Some inspectors will do that. I guess you are not getting inspected. That's ok. Good luck.

Jeff