I laid tile in the bathroom yesterday. About 18 hours later, it felt pretty solid, so I took the opportunity to do some minor plumbing work under the sink (replaced the water shutoff valves). I had some trouble installing the valves, and a fair amount of water dripped on the floor, but it's done now. I haven't grouted yet. In that area, the thinset in the grooves is now pretty much soaked. Should I be concerned about the strength of the mortar?

Also - can I grout now or should I wait until the area is thoroughly dried? I'm unsure because I've read that the drying of thinset is a exothermic reaction, rather than evaporation.

2 Answers 2


Thinset will normally be 80% cured after 24 hours for moderate indoor temperatures. 80% is enough to do any work on. At 18 hours you got some water on your floor. The water has little to do with your thinset now. What you are worried about with the thinset is putting pressure on it while drying.

Imagine glueing something like a magnet to another piece of plastic with something like gorilla glue. Let's say at the 20 min mark you move the magnet - even a little. Will it be glued as well and hold up as good? No way.

But the water didn't really put pressure on your tiles to move them unless you had a ton. Now you standing on the tiles while plumbing is a different story. However what are you going to do? If you moved the tiles a little and killed the bond then it will pop out on you eventually and you will have to fix it. Unless something is moving on you now there isn't much you could do with it.


Regarding strength, what's done is done. I wouldn't worry a minute about it and certainly would not start taking up the tile in the off chance that somehow the mortar has been weakened.

In fact it can be helpful to keep mortar/cement/concrete damp for an extended period.

The spilled water does put an additional temporary moisture load on any wooden substructure, but again, this would be negligible in light of the original water content of the mortar.

  • That's great to hear! The subfloor is concrete, so no problem there. Do I need to wait until it dries to do the grout?
    – Elliott B
    Jul 16, 2013 at 3:05
  • If there is any standing water where the grout is going, I'd clear it with a wet-vac, then grout.
    – mike
    Jul 16, 2013 at 3:15

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