Do I need to use special grout for tiling the shower floor?

Question

The builders have left and the grout in the shower on the floor has cracked and left spaces between the tiles, the same thing has happened in the other bathroom which has underfloor heating.

Answer 1

I second everything that the other poster said, but want to add that the subfloor may also not be level, which can cause the grout to crack.  It should have been checked & fixed or replaced before the tile was installed.  If the tile installer has to rip the floor up to fix, then make sure they get the subfloor perfectly level before they proceed.  If it is not, the tiles themselves make start to crack over time, in addition to the grout.  Although, the grout usu gives first, protecting the actual tile.  Good luck!

Answer 2

  The under laying cause needs to be determined.. It sounds to me the tile is coming loose for the grout to come out as you describe..  Rap on the tiles w/ your knuckles. Do it where the grout is loose and off to one side where it seems to be holding.. If the loose grout tile sound "hallow" then they have lost the bond and need to be fixed..Either way the builders/ installers need to come back and address this issue..Any grouting at this point  will be a waste of time and $ till the under laying cause is fixed  GL