splitting grout

[Unregistered]

hi, i recently renovated my bathroom. stripped all walls, replastered, pva sealed the walls, re-tiled walls with adhesive+grout, let it dry and now i amgoing over it again grouting it. I have done exactly as the tub said, exactly what my father in law said and my collins DIY manual said, which are all the same practice. After i finished an area i grab a coffee go back to admire and all my joints have tiny blow holes in the centre of the joint with a line/indentation running along it.
Please help as i am going insane!!!
I was told by a tiling shop its cause i am using a adhesive+grout solution and it needs to be just grout. tried this and its doing the same.

 

[Gazzer]

1st http://www.tilersforums.com/tile-adhesive-grout-substrate-preparation/2511-p-v-versus-primers.html
2nd what tiles have you used ? ceramic, Porcelain , Stone ?
3rd the pin holing you describe wil be down to not getting the air out of the joints when tooling the grout in, it can also be caused by over wet grout either in the mixing process ( obviously not in this case) or washing off with too much water.
4th The shop is correct in that Adhesive to stick the tiles and a Grout to grout.

 

[Unregistered]

thanks, i was worried my sponge was too damp but i cant ring it out anymore, i did try an area witout wiping it off and it still split. no pva used on the joints just the bare walls before i tiled. they are just basice white glazed porcelein tiles. 4mm joints.

 

[Gazzer]

Are you sure they are porcelain if so you should have used a polymer modified grout and adhesive !

 

[Unregistered]

Sorry, its says ceramic on the pack

 

[Unregistered]

sorry they are ceramic

 

[Unregistered]

Are you sure they are porcelain if so you should have used a polymer modified grout and adhesive !

sorry ceramic

 

[Unregistered]

hi sorry i dont know why its not replying, they are ceramic glazed white tiles. not exspensive just normal 400 x 250mm.

 

[Martyn Leeds]

Re grouting:-
without seeing any pics, it sounds to me its just the washing off process.. either too much or too little, the grout in the joint isn't being smoothed off maybe - and its drying out with patchy bits/holes??

but 4mm joints on the walls?? I presume its not a grout for wide-joints. prob say 2mm ish on the tub?

 

[Gazzer]

What adhesive /Grout is it that you have used ?