It's my maiden voyage on placing concrete board and subsequent ceramic tile installation. I have unfortunately failed to notice an unlevel corner in the bathroom where I'm working. Now my last piece of concrete board--in a small toilet alcove -- is mortared down and slanting down, with a slight high spot right on the seem of the last piece. I used floor leveler prior to putting down the other pieces, but somehow missed this slightly down hill area--presumably from a warped floor joist.

My question: Can I effectively level in this small area on top of concrete board using the thin-set mortar and one or more layers of mesh tape--let that dry, and then install the tile on top of the dried mortar?

If not, are there any solutions other than ripping up the concrete board and underlayment and applying an appropriate floor leveler under the new underlayment?

Thanks for any info-- I'm really upset about this problem and am about ready to put underlayment and vinyl down on top of the concrete board.:mad:

Thanks again.

You can build up with mortar to get that spot level, especially if it's a spot that will not get high traffic. Make sure your mortar patch is large and properly feathered. I'd also double the number of screws around this area because that board is under a slight tension, hopefully you glued and screwed the board to begin with.

You can build up with mortar to get that spot level, especially if its a spot that will not get high traffic. Make sure your mortar patch is large and properly feathered. I'd also double the number of screws around this area because that board is under a slight tension, hopefully you glued and screwed the board to begin with.

Thanks for the info. I will endeavor to level/feather the area with modified thinset mortar reinforced with appropriate tape, let that dry, and proceed with tile installation. The area is small, and as long as the mortar won't break on the feathered area, this solution should work. The concrete board is mortared and sufficiently screwed to the underlayment grade plywood.

Thanks again for the input.:)