How to install cement board on a shower curb and not pierce the waterproofing

This technique can be used over a PVC liner that is wrapped over a 2x4 stud curb. This technique is the same as when a form curb overlay is used, referred to as a preformed curb on page 258 under common shower configurations in the TCNA handbook , the difference is that the overlay is made by you. While there is nothing wrong with foam overlays, they can be a little tight and may develop a twist as they are installed. This technique makes it so the board can be customized when dealing with the liner. If the liner is bunched or tight, you just need to make an adjustment in the size of the top face. A cement board curb is slightly easier to adjust when correcting for level and slope than a foam overlay is.

Lath and mud is still a good alternative but the preformed method can actually be easier to correct for level and slope. Mud and lath requires a slightly higher skill set than the method here, but mud and lath has no structural advantage, in spite of what some pros may say.
The thinset mortar used in this process is not used to adhesive bond the cement board to the PVC liner. It is used to complete the mold that is essentially being made when the curb is wrapped with the cement board. Think of it like this; If I took a bucket of thinset, turned it upside down and put it over your head and let it dry, you wont be able to get it off. Is that because the mortar stuck to your skin? No. It is stuck because the mortar dried in the form of a mold that contoured the entirety of your head. When someone goes over a liner with lath and mud they are doing the same exact thing with different materials. Essentially creating a mold that will hold similar to an uncoupling system used on floors. This is essentially an uncoupled curb. Think about it and then give it a try.
Now think about this...
Tile guys are a stubborn bunch and every one of them thinks they're the best. To those of you that feel you're the best, I'm sure your mother agrees with you, send her my best!
One thing to note; The shower in the video is a TCNA B-415 cement board traditional/water in-water out receptor. Cement board can be installed on the curb lower than the height of the shower pan mortar. Fiber cement board cannot be installed below the height of the shower pan. This goes for coated glass mat water resistant board as well. The only other board in the handbook that states the board may be installed below the height of the shower pan is Cementitious-coated extruded foam. This technique can be done with foam board as well, but 1/4 inch cement board is relatively inexpensive and still makes for a very strong curb.

Видео How to install cement board on a shower curb and not pierce the waterproofing канала Trendsetter Tile & Stone