A.Michael Byrne responds: It may be possible to repair the existing curb, but you will get better results by pouring a new reinforced curb that is bonded to the old concrete with a concrete bonding agent. You will have to ensure that there is no wax, oil, grease, or soap scum on the face of the concrete slab that could ruin or reduce the bond. After that, I recommend that you install a sloped shower pan to contain the shower water and prevent harmful organisms from becoming resident in the surrounding walls and floor.
As for hot-mopping the pan: In many areas, local building codes still allow unprotected concrete to be used as a base for a ceramic tile shower stall, even though the practice is not sanitary, is not approved by the UBC, and is not sanctioned by the tile industry. I haven't recommended hot-mopped shower pans since 1974, when health and safety...
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