Need assistance with Ceramic tile

Hello to all. I am assisting a frind in a DIY Laundry Room. Dims of the room are 18' 4" x 7' 8". Floor is 2x8x8' on 16" centers. 3/4 sub on joists. We laid 1/2 Cement Board last weekend with thinset and over 400 screws. He taped and thinset the joints. When dry fitting the 12 x 12 tile, we found that several of the joints are causing the tiles to "rock" side to side or corner to corner. We have heard alot about nail/screw heads causing tile cracks.
1) Do we need to fix the joints and if so, how?
We are planning 3/16 gap between tiles and the layout looks good. We are just concerned with the rocking.

Thanks.

Sparky

 

Actually Sparky, the seams should have been taped at the same time the tile was installed then peaking seams wouldn't be a problem. Oh well!

If the seams don't peak too much then when the tile is installed the thickness of the thinset should "take-up" the peaks and they won't have too much effect on the tile installation, but they could. Use a 1/4" X 1/4" X 3/8" notched trowel and you should be OK.

Screw-heads won't cause tile to crack if there is plenty of thinset under the tile. Spread the thinset all in one direction and shoot for 100% coverage on the tile, 80% is acceptable but shoot for 100%.

 

Thanks for the reply Bud. So, what I am getting is that we should be OK as long as we use the 1/4" notch and run in straight lines, not curves like all the DIY shows demonstrate. You have eased alot of worry. One of the high spots is directly in front of the exterior door and will receive alot of traffic. The next question is how do we finish the tile in front of the door? When we built the room we were not precise unough and the exit door wall is not square to the room. It looks like we will need to trim the tiles slightly in front of the door. The opposite wall will have about a 4 x 12" tile along it. Should we shift the tiles slightly to get the minimum 1/2 tile width that I have read about on here? The cut tile wall will be under a work table so we are not concerned about a narrow tile there. We are hoping to use full tiles from the garage enterance (the non square wall) and along the old house wall. Thanks again for your assistance.

Sparky

 

You could always mix up a small batch of thinset and feather down your bump before you lay tile.
Kinda like you'd fix a drywall bump, but with much harder material.

If the rocking is slight, which it sounds like, then what Bud said.
If the rocking is more significant, then you might try the thingset first.

I'm doing exactly this on my current baths' mosaic floor that dips about 1/8 of an inch in about 2 inches along one wall.

 

Keep in mind guys that the floors substrate should be plane but of course it isn't in this case and that's why it is being discussed. It may not be that easy to fill & feather to correct the high spots. This really isn't correcting anything and it may be better to grind-off the high spots and start over.

The fact that the thinset will "build" some height under the tile may or may not be the saving-grace in these matters.

With acute changes (ups & downs) the mosaic tiles would show the imperfections much quicker than the larger tiles.

If the larger tiles teetor 1/4" (or so) when held down tightly on one side then you will be faced with some lippage when compared to adjacent tiles and this is an issue.

 

Thank you both for the support. We are pressing on and tiles over 1/2 the floor last night. We are wondering about the tiles we may need to trim at the door enterance and also the tiles at the old door that is now just an opening to the house.

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Garage Door (Standard Metal Door)

The Garage Door is a prehung exterior door will sill plate. The tile against the sill may need to be trimmed.
1) How do we address the jagged edge of cut tile at the door sill?

The house enterance had an exterior door like the garage. This has been removed and we are wonder what is the best approach for a transition from the tile in the utility room and the vinal floor in the hall.

Thanks again for all the assistance.

The rocking was no more than a 1/16 inch at the seam. We are installing 12 x 12" ceramic tile. So far we feel good and estimate 95 - 100% thinset coverage on all tiles.

Sparky

 

Sparky the tiles at the door thresholds are simply cut like any other cuts. Why would they be jagged? Those tiles should be away from the threshold about 1/8" then THAT crack would be caulked not grouted.

As far as transitions to a lower floor covering, this is almost always an issue. Maybe the best way to deal with this is to use a metal tile edging to finish the tiles in the door openings. Usually the opening is split at the center (the tile stops at the center-point). In the case of a door being in place the tile stops under the center of the door.
If the "old door" that has been removed is to be replaced then this should be done before the tile goes to that point.