Tiling kitchen. Floor uneven. Going crazy!

allfy16

Hi, I am new to pretty much everything DIY but am trying to learn so that I can fix up/repair/renovate my house myself. Any help is greatly appreciated.

I am attempting to tile my kitchen floor but am running into some problems.
First, the kitchen floor had a hump running down the joist in the middle of the floor. I removed most of the OSB subfloor and found that the joist was causing the hump and was about 3/4"-1" higher than the other joists. So I ground it down and installed 3/4" plywood.

Then I noticed the plywood I just put in was still raised up and sloping from the joist I just ground down. The unevenness didn't seem too bad so I went ahead and put down some thinset mortar and began laying the cement board on top and screwed it down.

After laying my 4th board, I placed a tile on top of one just to make sure it lay flat. When I pushed on the edges of the tile, the other side would raise up slightly (I would guess around 1/16").

Fearing the unevenness of the cement board and raising of the tile would make tiling the floor impossible, or end up cracking the grout and/or tile, I got frustrated and quit for a couple days. When I resumed working, I took up the cement board then spent 2 1/2 frustrating days scraping up the dried thin set mortar.

I also noticed that the original OSB subfloor that I didn't cut out is raised up to 1/8" above the plywood I installed, but then is flush with the plywood in other spots along the same joist. Should I chisel it down?


So...What can I do about evening up the subfloor? I bought some self leveling underlayment (Henry 565 FloorPro) but it was $36/40lb. bag, and the directions say it only covers 43 sq.ft. at 1/8" thickness. My kitchen is about 120 sq.ft. so if I had to level the whole floor with it, it would cost about $120.
Could I just use more of the thinset mortar to even out the low areas, or would the cement board still lay unevenly?





Specs:
Kitchen-120 sq.ft.
Thinset Mortar-Mapei (it's polymer enriched!)
Subfloor-3/4" plywood and 3/4" OSB
Joists-16" on center
Tile-12"x12" porcelain
Cement Board-1/4" UltraBacker

Any help is greatly appreciated!

oh'mike

It's to early to think------

All flattening efforts from this point will be done from the top of the backer board.

Set the board into a bed of morter and nail it down---roofing nails spaced about ever 8 inches---or screw if you prefer--

Them use the self leveling compound----read the bag---I believe henrys requires a primer----I use Jif-set and mix the first layer with a liquid latex

I can't help the cost----tile setting can be costly to do properly-----and very expensive when done wrong.

only a small amount of correction can be acheved with thinset----to much mud and the tile will drop as the thinset settles and cures----

Leveling clips can be used during the instalation-----they work well--but add a lot to the cost of installation.

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