Greetings,

I have a traditional tiled shower with curb, maybe 20 years old, with questionable build quality. We think it may have been sloped wrong from the beginning so water puddles.

Is it feasible to pull the tile, build up some additional mortar and thinset on top of the mortar that's there, and retile? I would add an inch or two at the walls, tapering to zero near the drain to avoid messing with that.

Would this work, or am I fooling myself? Do I have to rip it out to subfloor and start over?

Thanks much!

If the finish work is questionable, I imagine what is underneath might be the same...or worse.

I would at least take up the tile on the floor and on the curb. The curb is one area that is usually neglected when it comes to waterproofing, and what you see under there will give you an idea of what the rest of the shower looks like.

Actually, after 20 years, a conventional shower is probably due for a rebuild anyway. If it still drains properly and you can get by replacing only the floor tile, that's certainly a cost-saving option.

Thanks for the answer.

I guess my question was mostly about the wisdom of laying new mortar and thinset on top of old. Are there any chemistry surprises there, like the "moisture sandwich" we see in other postings which pertain to completely overlaying a whole new setup on top of old, as opposed to just adjoining new and old mortars?

You really can't taper mud down to nothing. About 1/2" is as low as you'd want to go with it.

If you're set on not taking up the mud bed, then just take up the tile, fix the low spots with thinset, then retile.

If you have spots that are more than 1/4" too low, you'll want to fix those in more than one application, letting each one dry before starting the next.