cracking grout on wet room floor

[jstone]

I had a wet room put in over the summer by a local company but the grout round one of the tiles near to the waste drain in the floor keeps cracking and coming out. They have come back and regrouted twice once with normal gout and once with some additive but it still breaks up. Any ideas/ suggestions would be very gratefully received

[Dave]

There is either movement causing it to keep cracking or water may have got into the substrate causing a weakness...I would get this investigated before it cause's to much damage...could be a simple repair or a faulty installation....what type of substrate is it onto and what prep work was done..i.e..tanking or membrane...?

[guy1976]

some wet room trays need the waste drain to be boxed in under the floor boards and then filled with cement so when you stand on the drain there is no movement, what type of tray have you got?

[uug197h]

we have had to repair one that someone else hat fitted they had mounted it on silicone and not supported the base, there are 2 ways to fix the problem 1 is to remove the base and do it right, the 2nd is to remove part of the ceiling from the room below and put in supports under the base then re-grout

[Leatherface]

Impossible to answer unless I know what kind ( make and manufacturer ) of wet floor it is !!
For example some wet floors such as supplied by Mapei, which are cement board based need very little preparation prior to tiling ( although I do recommend that they are tiled using cement based and latex additive (( instead of water )) )
Other wet floors such as the "Tuff Form Wet Floor" require sanding and definately use of latex with your adhesive !! As these are a plastic type wet floor.
The only possible reasons for the grout cracking are.........

Incorect grout - not flexible
Excess movement in wet floor
Incorect preparation of wet floor prior to tiling ( i.e not sanding of plastic prior to tilinng )
Incorect adhesive used.