I am doing a tub to shower conversion using a mortar bed and Hydroban for the walls. After hanging the Hydroban, one wall puckered inwards at the seam by maybe 1/8", which I thought would be a problem, so I got the plastic screeds that Isaac sells and screeded it using thinset so it was flat and plumb.
After a few days I noticed a horizontal crack in the thinset, but figured it's concrete, and concrete cracks so whatever. But today I was finalizing the tile layout (rectified 4 x 4" tiles) and realized that the crack was due to the wall buckling outwards now. It's out by maybe 1/8", but these rectified tiles (Sant'Augostino pixel tiles) are not tapered at the edge at all, so will really show any lippage.
I've waterproofed the whole thing, and it's got a heated floor (Ditra Heat), so I don't want to do the obvious tear-out and fix it route, and hoped people might have suggestions.
The first picture shows the wall in question (on the right). It went inwards right at the seam, so in the second picture I have used the plastic screed boards to get a plumb surface, and in the third picture it's after I have screeded and it's dry. It was perfect! The fourth pic is of the crack, and the fifth is how far out it is. It's still plumb and flat on the right side of that wall (by the drywall), but it's totally coming out at the pony wall on the left.
Thanks for any advice!
Any thinset is that is adhered is good. It typically takes about 3 days for the thinet to cure. After that, its not moving.