Badly teetering tiles

ol rick · 01-19-2012, 07:22 PM

I have my kitchen floor covered with new 1/4" backerboard attached with 50 screws per sheet and mortar beneath. At 50% done with new tiles, there are two separate areas where the 12 x 12 ceramic tiles teeter so badly that even me, a first timer, know I should not lay those tiles. I tried grinding the board's high spots down some with a 5" grinder, but did not stop the rocking tile. These spots are not at a backerboard seam! What do you recommend is best way to make it flat?

**oh'mike** · 01-19-2012, 07:31 PM

You should have checked that floor with a straight edge before you started----

Stop----remove the tiles in that area and check the floor--

You will be needing self leveling compound and primer to remove the variations

You may need a bigger toothed trowel---what are you using??

ol rick · 01-19-2012, 07:45 PM

Yeah, I did look closely at the floor prior to putting the 3 x 5 sheets of cement b-board in place. But they are all down completely. The tiles that arew teetering are not mortared in yet. The first tile that teeters badly is next to installed tile (no grout yet), and about 18" of backerboard on the other side to the wall.

The second tile that rocks is in an area where no tile has been set. Only backerboard. Must be some kind of "hump" in the b-board but I cannot really see it. I tried using a tile on edge, upright, to see specific spots where it pivoted, then used the 5" grinder to work that spot down. Not much luck, but could tell a slight difference after I grinded.

**oh'mike** · 01-19-2012, 07:52 PM

The floor is just fine except for a couple of small 'bumps'?

If that is the case---take a chisel to the high bump and remove as much of the backer board as you need---

Thin set --and move on--

You say it's just a bump--as if you might have left a nail or trapped some debris under the backer?

**oh'mike** · 01-19-2012, 07:54 PM

You need a 5 foot straight edge to properly check for flat---

What size trowel are you using?

ol rick · 01-19-2012, 08:00 PM

Yes, the b-board seems to have a hump of some kind but very very slight and cannot see it. When I place the 1/4" tile where it will go in, it rocks from one corner to the opposite corner about 3/16. I do not think the b-board has anything under it - nail, debris, or any junk, because (being a newbie) I vacuumed the 3 x 5 area carefully with a shop vac so I could be sure. I put all my weight on the board as I screwed it down, starting from the center of the board and working out to edges.

Now if I take a chisel to it, whould I chisel out the mortar too? I can't really tell where that hump begins or ends, it just makes the tile rock.

Oh yea - I used a 1/4" square notch trowel.

**oh'mike** · 01-19-2012, 08:26 PM

Remove the top layer of the backer board only---You need to chisel and peal back just the hump

**oh'mike** · 01-19-2012, 09:01 PM

I use 1/4 x 3/8 for 12x12---1/4 x1/4 is acceptable--I think it is to late to change half way through the job----Mike---