Floor Tile Grouting Cracking

[CityTiger]

I had my bathroom donw almost a year ago with black floor tiles and black grouting.

However, parts of the grouting keeps cracking. The blook has been back and redone the cracking parts a couple of times but each time either the cracks re-appear or the bits he did lift out (assumedly he should have raked the grout out where it had cracked and redone it from scratch?).

We do have underfloor heating but that was left off for over 24 hours after it was done to allow it to dry out.

Just wondering if its normal or if it indicates bad workmanship or cheap grout? I dont know what grout he used although I do know it was hand mixed.

[m3 fitter]

The most common cause of grout cracking, is an unstable substrate, ie: the suspended floor not being strengthened enough, i suspect 1/8 ply has been used, or nothing at all on the T&G chipboard. If this is the case, only a retile with the correct rigidity will suffice, do you remember what he used on the initial flooring to strengthen it?

[CityTiger]

I dont know what he used for sure but from memory I would say the chipboard he put down was getting on for half an inch thick. I know after he did it the floor was around an 1 inch higher up - thats with the chipboard, underfloor heating and tiles on.

[royaloakcarpentry]

25mm higher after overboarding, heating matt, latex, adhesive and tiles is a good indication that he has bodged the job.

Just from the info of how much higher the finished floor level is compared to before the job was completed, I would have a fairly good guess that it needs to be ripped up and done properly.

best case scenario is that he used normal grout instead of a flexible grout and this is infact the cause of the problem. I rather doubt you will be that lucky.

[CityTiger]

Oh dont say that!

How much higher would you normally expect the floor to be if it had been done right?

I think its something we may have to put up with if thats the case as ripping it up and redoing it would be a hassle....and probably extra expense too given some tiles would most likely need replacing.

This is one of several problems we have had with it....sometimes I wish we had never got it done!!

[royaloakcarpentry]

The finished height of the floor all depends on what tiles were used. On average for a ceramic tile without underfloor heating and laid direct onto the sub floor, the finished floor level will be about 13mm above the sub floor. So that would only leave 12mm on your floor for over boarding, heating matt and latex.

[CityTiger]

Ok thanks - I have emailed the guy and asked whether he used flexible grout and what thickness of board he used - so we will see what he says. I could always take off the bath panel to find out for sure on the board thickness but would rather not if it can be helped to save having to reseal it on again.