I am remodeling a bathroom in a 39 year old house. ! will be installing 12 x 12 ceramic floor tile over plywood underlayment. Originally had old sheet vinyl. Because of the differencein height between bathroom and hall finish floors, which are staying, I will have to keep my adhesive / thinset as thin as possible. I will have to install a thicker marble threshold that will have about a 2" wide by 1/4" taper downward on the hall side,to the hall floor. Has anyone used mastic, premixed thinset that does not seem to have sand in it, or thinner than normal layer, (smaller notched trowel), in a large tile situation like this? Tried a couple tile places that suggested all kinds of expensive options because I didn't want to buy their tile. Thanks for any info anyone has.
you can skip the mats and uncoupling sheets - they are just costly diy garbage sold to shortcutters. put down a layer of 6 oz fiberglass mesh for crack isolation and stopping deflection in the floor. however, you are not going to be able to get away from the fact that tile has to be laid with enough good quality polymer modified cementitous mortar under it. 12 x 12 needs at least a 1/4" square notch, and will be better with a 5/16 square. you cant use mastic on a ceramic tile if you want it to stand up over time. they must be bedded in a mortar, not an adhesive (glues are for flexible floor materials, mortars for rigid materials)
fyi - you can install a thinner threshold if you wish, you just install it on a slope when you bed it in the mortar. it gives a nicer look and there is no huge lip - just a smooth transition from floor a to floor b