I set the bottom row on something solid. Whether that is the tub (with spacers under them to give the proper gap), the tiled shower floor which was set the day before or a ledger board. I use hard ‘marble horseshoe’ spacers which don’t compress as weight (more tile) is stacked upon them. As long as your bottom row is supported every row will support the row above it.

When installing tile (I am using 12″x12″ tiles) on a shower wall, what methods have you used in the past to hold the tile up before it dries? I don’t think the thinset will keep it held up when wet.

Thanks for the help