Concrete Board Not Level despite level framing
Our concrete board is not level, but I don't know why. We leveled the framing with the laser level and cardboard shims, and double checked with our 6ft level before starting with the concrete board. I took down one wall that was worse (I didn't take a picture before I took it down) because I thought we must have messed up the leveling of the framing, but when I double checked it was all level!
In the second picture, the level doesn't have space at the top and bottom but seems to move inwards towards the middle of the level.
My husband said the Durock is not 100% flat. We are also cutting the board with an angle grinder with a masonry blade. I'm not sure if that has anything to do with why the board is not level. Is there a trick to drilling into the board that I'm not aware of? We're not sinking the screws past flush with the board. Please help!
Also, is there a certain degree of wiggle room we can consider with the leveling, i.e. Within 1/8in is okay?
yes, 12x24 will be fine on that substrate