[Jplster]

4 years ago I installed 234 sq ft of 12 x 12 tile with thin set mortar in my kitchen.

I have a 70 yr old raised house with 19 1/2" oc 2" x 9 1/2" (actual measurement) joists spanning 12 ft.
The subfloor is 3/4" x 6" wood planks laid diagonally.
Above that i nailed with a framing gun, a 3/4" T&G sub floor.
I used framing nails with glue on them.

I put the tile directly on top of that with thinset mortar.

The tile is cracked to the outline of the T&G subfloor, the cracks are exactly where the 3/4" T&G subfloor butts together. I weigh 290 lb. and occaisionally have heard the tile crack as i walked on it. What have i done wrong?
I now, want to remove the cracked tile and start over.
What shoud i do?

 

[Clutchcargo]

A couple of questions.
What was the orientation of the new T&G subfloor; parallel or perpendicular to the joists?
What size are the joists?

 

[Jplster]

the joist span 12 ft. their actual size are 2 x 9 1/2 inches, I crawled under the house and measured them. they are 19 1/2 inches apart.
I laid the 3/4" T&G plywood perpendicular to the joists.

 

[Clutchcargo]

I think what's happening is that you didn't use a decoupling component like hardiboard or ditra. So the differing expansion/contraction of the building materials is causing the tiles to loosen.
Someone with more experience can pipe in.

 

[rusty baker]

I think what's happening is that you didn't use a decoupling component like hardiboard or ditra. So the differing expansion/contraction of the building materials is causing the tiles to loosen.
Someone with more experience can pipe in.

What you said sounds good to me.

 

[Bud Cline]

...and this is why you don't install ceramic tile directly to pywood.

In addition, the underlayment probably should have been installed in two layers because of the 19.2" joist separation and the joist spanning being extended to the limits.

 

[Jplster]

sorry I have discovered the problem

Underlayment like ditra will not stop the floor from flexing up and down, it does stop expansion and contraction. The solution is to either add more floor joists or to put in a felxible tile. The diagonal 1 x 6 subfloor has too far to travel between joists, 27.5", so with the subfloor flex and the joist flex it is too much for the ceramic tile.

 

[Bud Cline]

The solution is to either add more floor joists or to put in a felxible tile. The diagonal 1 x 6 subfloor has too far to travel between joists, 27.5", so with the subfloor flex and the joist flex it is too much for the ceramic tile.

Which is why a "double layer" of subfloor is required so as to reduce deflection of the subfloor material BETWEEN THE JOISTS.:yes:

 

[oh'mike]

Joists deflection is acceptable for ceramic 465 if the joists are hem/fir--

You need durrock or ditra--Wood expands and contracts tile does not--the cement board will help-------The double layer of underlayment could not hurt.

Also check on the humidity of the area below---I've seen a damp basement damage a tile floor above it.--Mike--