I need to tile over an old shower made of concrete blocks the kind used to build with. Do I need to use a glue, some type of sealer or what? I am using a cheap ceramic tile from Lowe's. Thank you for any ideas.

Lorna

You would be better to use thinset mortar, such as FlexBond, than an adhesive. You may want to skim the block with the thinset first to smooth any bumps or ridges. Let it dry and then, using a knotched trowel apply the thinset and then place your tile.

A wall made from cement block is never perfectly flat but your ceramic will not bend so you need to check the wall for flatness. If there is any variation I would attach 1/4" Hardibacker to the block and then set the tile with thinset.