Floor grouting break up

[UCANDOIT]

Hi all
Just renovated my bathroom but big problem with floor grouting.
It's constantly breaking up.

Floor is level, tiles are all OK, used Unibond waterproof coloured grout but it's doing my head in.
Used the same grouting everywhere else and it's fine.

Any one got any ideas????

[skiking]

Sounds like the floor is moving. What have you put under the tiles ?

[tim'll fix it]

did you overboard the floorboards with 12mm min WBP ply
did you use flexible adhesive
did you use flexible grout

[Only-Me]

If not................then http://www.youtube.com/watch?v=NBikNb5oEcU and start again

[UCANDOIT]

Thanks for fast response


Screwed 8mm MDF to floor boards to give flat even surface.
UPV'd as directed by Unibond grout.

[skiking]

Thanks for fast response


Screwed 8mm MDF to floor boards to give flat even surface.
UPV'd as directed by Unibond grout.

Think that could be your main problem

[bathstyle]

Yeah, a classic mess up, not only did you use the worst type of board imaginable, it's also too thin and you primed it with the wrong product.

Rip it all out and do it properly, if you need help, ask.