Kitchen tile install SLC Hardibacker [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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04-14-2010, 01:53 PM
My first post on here but I have been using this board for over a year as a resource, and what an excellent resource it is!

I am in the beginning stages of tiling my kitchen with 20x20 ceramic tile in a diamond bond pattern over 3/4" TG pine floor. I had to patch a few holes in the floor, using 3/4" OSB and added ledgers under them on the joists for more support, as well as adding a few 2x4's in higher traffic areas for support between longer joist spans (20"). Probably overkill but ...

I'll take some photos and post them here later tonight for better visual, but essentially I'll be tiling the kitchen, laundry room, half-bath and a through way with a closet and also exit to side door. I think I figured its about 225 sq ft.

Problem is, between kitchen and through-way opening, the floor is concave about 1" or so. I asked my GC what to do and he said to level it with thin-set under the Hardiboard, then tile on top of that. But from what I've read on here, I should either install hardiboard directly on clean subfloor OR put 1/4" thin-set bed on subfloor, then install hardiboard and THEN level the floor out. I know I need to do something as with the larger tile area anything not flat would start popping tiles.

Any advise would be greatly appreciated.


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04-14-2010, 01:57 PM
Best thing to do is find out why it's sagging there and fix that problem. If you got damaged joists or subfloor, no amount of leveling will fix the problem.

04-14-2010, 02:07 PM
Alex, let's start with the basics. Tell us how your floor is constructed. Size, spacing and maximum unsupported span of the joists. Thickness, type and number of layers of your subfloor. If you are unsure of any of these terms, ask and we'll explain. It's important that before you spend a lot of money and time installing those big tiles, you make sure that your floor can handle them.

04-27-2010, 11:58 AM
Finally getting ready to tear into this as I've been on the road for work. I'll have to measures the joist spans, but I believe they are mostly 16" OC, although there are a few that are 20", which I went and put 2x4 bracing between joists and also cut out 3/4" OSB and glued/screwed tightly between joists to underneath of sub-flooring to strengthen up a bit. Several of the joists I sistered to add strength/try and level out floor.

The kitchen is about 150 square feet, although I plan to just tile up to cabinets (not under). Also, there is an adjacent laundry room and half bath along with a walk through. I'll have to take pictures tonight to better illustrate what I'm talking about.

Subflooring is 95% 3/4" tongue n groove pine nailed down to joists. there were a few sections rotten out that I cut out between joists and put 3/4" OSB in place.

Does this help?