Need Advice On Grout

[HABSFAN]

A few months ago I replaced the carpet and linoleum floor in the hallway, kitchen, dinette and bathroom with tiles. Before installing the tiles, I added 3/4 inch plywood to my sub-floor in order to properly support the tiles. I used 2 inch floor screws to secure everything in place (every 6 inch), making certain not to put joints on top of each other. I did leave approx 1/16 inch between each 4x8 sheet of plywood for expansion. Once all the tiles were installed (using cement), I waited approx 2 weeks before doing the grout.

A few weeks after all the grout was done, I noticed that the grout in the kitchen was coming off (around approx 15 tiles in a row).

Going to the basement I notice approx 1/32 inch space between the TJI and the underfloor in the kitchen. So, after removing (destroying would be a better world) 15 tiles, I re-screwed the floor, but this time, with 3 inch floor screws, making certain to tap in the TJI. Following this, I re-tiled and grouted this area again.

To my dismay, the following day, the grout come off ...At first I thought it was just a fluke, so I cleaned the area again, and re-grouted. This however did not last one day...

Because of the amount of tile that have been installed, approx 300 tiles, putting epoxy instead of grout is not an option...(would take me forever to remove all the grout) and I want to keep the same colour grout everywhere!!!

My question is: is there a product that can be added to the grout (I'm using a colored grout - delorean gray) to hardened this...I would like use this only in that one spot were the grout is not staying, or does anyone have an idea to deal with this...

Seems that a simple weekend project has just got very complicated...

[Scooter]

The way I read this is that you did not use a backerboard--only plywood?

If that is the case, that is the problem and it is unlikely that there is a product that will stay put while the plywood is moving in one direction and the tiles stay put.

[Hamilton]

Hi Habsfan, gotta first name we can call you?
Sounds to me like you have excessive movement in your joists.
No matter how much you screw the plywood, if the joists are flexing
too much this problem will continue to happen. Measure the greatest
unsupported span of your joists, note the type, size and spacing of your joists, and
come back and use the deflectometer found just above labeld deflecto.
If your joists have too much deflection post your information here
in this same thread and we can help you beef up the floor. If it is
in fact another problem we'll do our best to help you get to the bottom
of it.

[tilelayer]

when you say you used "cement" to set the tiles, what do you mean? Latex Modified thinset, Full Flex, Quick Flex, Medium Bed Mortar? Masons mix? be more specific

[HABSFAN]

First of all thanks for the advise and my first name is Mike.

The tiles are cemented with fortified tile cement. When I removed the 15 tiles to take a look at the sub-floor, I used a pre-mix tile cement (which I bought at Home-Depot) to re-instal the tiles.

Tell you the rest of the tiles and grout I don't have any problem exept for that one spot....

Mike

[pitterpat]

Bad idea to use the premixed.