Hey there, i just finished the tiles in my house and i am having this problem in a couple places. this is the section that my grout was a little too wet but i used it anyway could it be the problem ?

i used Chembond adhesive and mapei ultracolor plus grout, sub floor is 3/4 inch OSB 3/8 ply, screw at 3 inches square, 3/8 thick tiles, 3/16 spacing

there is no movement on the floor, im really wondering if too wet grout and not pushing it in enough is the problem. this is the only section where i failed the mix the other parts are fine

thx for the help

hi when you say tile edge do you mean the edge of the room where the tile meets the wall?

between tiles laid on the floor, it seems like the grout did not stick to the side of the tiles at some place, as if it would have shrink

with mapei ultracolour, you have to follow the instructions to the letter, it's a formidable grout when mixed properly. I think it probably is the reason, although your ply should also have been at least 1/2 inch.

As Doug has stated, the ply is far too thin, lateral movement?

What spacer size used, too narrow or poss too wide?

Originally Posted by boxer1van

What spacer size used, too narrow or poss too wide?

wouldn't matter,the main thing here are the ply is too thin!

3/8 ply is all we use in Quebec and i never had problem this way, but yes maybe i could have taken thicker one theres another 1/8 sheet between my 3/4 and the 3/8, the stuff they use to put linoleum on, should i have remove this piece ?

Have you done a deflecto test on the joists....

Your sub-base should be fine.... what Standard is the thinset..? is is modified in anyway.

You can do a joist deflecto test here>>>> The Amazing John Bridge Forums Deflect-O-Lator :-)

High-Performance, Polymer-Modified Floor and Wall Tile Mortar
MagniFlex Ultimate 8830 is a high-performance, polymer-modified, single-component, thin-set mortar for setting ceramic tile and dimension stone

Deflecto :
For joists that are SYP or Douglas Fir, in good condition, 9.25 inches tall, 1.5 inches wide, 16 inches on center, and 14 feet long between supports, the deflection calculated is 0.442 inches.

This translates to a deflection of L / 380.

Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Ceramic tile, Congratulations!


Seems like im just a hair good enough for ceramic tile, would adding more wood cross under the floor help ? or another hanging beam halfway to distribute the weight ?

but i dont thing structure is the problem, the half section i did with the grout mixed well did not crack at all .... or not yet

OK all is well...

I think you need to remove the bad area's of grout and re-do them..

hard to see, had to wet the floor to see it, its just a couple weeks old i hope it doesnt get too bad. Any electric tool working well to remove grout ?

A quick question.. did you walk on the floor before the grout was set.?

yes i probably did

OK.. That could have caused it to deflect slightly and break the bonf between the tiles and grout...

Best thing is to re-do those area's.. grout and wash off then leave to set..

A fein is a good tool for re-grouts.. Ultracolour dries hard..

alright thx for the help, ill wait a couple months to see if it all holds up and regrout the places that needs it