"Grout cracking & flaking" Topic

I had the bottom portion of my shower redone by a contractor, but did the grouting myself. After about a month, I noticed the grout had cracked & flaked off in a few places. So I started the laborious process of digging the old grout out to do it again.

But, now that I get down at the floor level & look closer, I see that at least half the floor has hairline cracks running between the grout & tile. I don't know if it's just s slight space cause by the top of grout shriking & pulling away from the tile as it dried, & the grout below is still fine. Or if it's an actual crack that goes all the way down. So, should there be any cracks like this at all? What would cause these kind of cracks? For some reason, the walls seem fine.

Also, in some places the grout's so weak, I'm able to flake it off with my finger. I'm assuming this shouldn't be happening. Any idea what the cause would be? Some of the tiles are pretty close together, so the grout might not have gotten down in between the tiles.

For either problem, did I do something wrong with mixing or sealing the grout?

Thanks for any help

If your tiles are too close together you are asking for trouble in the future – eventually they will 'lift' due to normal contraction and expansion due to temperature differences. It's always a good idea to use spacers.

You can expect a few hairline cracks due to shrinkage anyway. As you made up your own grout from a powder, you may have used too much water. That would explain both the weakness and shrinkage. Also, the surface may not have been prepared well enough – if it was damp to start with, again you would have problems. As the surface was the floor of a shower unit, water rising to the surface would seem likely.

Of course, it depends on how 'bad' it really is – one person may say 'it's bad', another 'it's normal'. If it is really bad, I suspect you may have to lift them again, redo it with reasonable spacing, it might be an idea to 'seal' the surface first to prevent damp seeping through. Try asking the DIY store for advise on this if they have anyone on hand.

Personal suggestion would be to use a good quality ready mixed grout for this kind of work.

That sounds about right to me. I'm not an expert, but I've done about 6-7 tiles jobs. Sounds like the grout wasn't mixed properly and the tiles might be too close together. In any event, the grout should be pretty hard after 3 days. You might be able to make a mark with your fingernail, but it shouldn't come off. Did you use sanded grout? It's good to use sanded grout on the floor.

The cracks will allow moisture to track underneath the tiles – this might be why the new grout is lifting and is still soft (although I tend to agree with GM's answer). When you regrout (and I think you will need to do this all over again with a pre-mixed grout) you should allow a couple of days for any moisture underneath to dry out (a dehumidifier would help, but this needs to run for a couple of days).

Best of luck

Since this is in the shower it would be best to remove all of your grout. Let the subfloor dry out good and then regrout with a premixed sanded grout. Wait a full 24 hours for the grout to dry before doing anything else to it or using the shower. One reason for grout crcking could be a weak subfloor. If the surface beneath the tile is wood it should have been strengthened with another layer of wood/backerboard to prevent flexing

For a shower floor, you should also look at sealing the grout after it sets.

And like others said, make sure you use a sanded grout.

Sounds like a grout problem; if the grout was good and the floor sprung underneath from walking on it, the tiles would crack, not the grout.