DaveChester wrote:
I have purchased a Grohe frame which I have bolted to the wall and
floor, covered in 18mm WBP ply and then tiled. I left it a day or two
and then bolted the toilet on, no problem.

I have now noticed that the bottom two tiles have cracked from the
pressure of the toilet bearing down (toliet anchors at the top so there
is quite a lot of pressure near the U bend). I am quite heavy but
obviously I cant have this happening again. Has anyone any tips on how
I could do this better?

I installed a Grohe frame, and had a similar problem as my 18mm MDF
backing board bent slightly under the lever force created at the base of
the toilet. Seems to be a design flaw in the frame that there is no
crossbar for the base of the toilet to rest against.

My solution was just to wedge some wooden braces between the board and
the rear wall to stop the flexing. If you're lucky you'll still be able
to insert some offcuts through the hole for the U-bend if you can
dismantle it in situ.

Vaci