Subflooring [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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12-11-2004, 05:04 PM
I am planning to tile a floor that was built in the 20's. The deflecto says I am ok - 470, but there is no plywood in the subfloor. The 2" wide joists are on 18" centers. They have full 1" thick subflooring (pine I think) placed at a 45 deg. angle to the joists. On top of that is 3/4" x 2 1/2" pine tongue and grove flooring. Is that ok for a base?

I plan to thinset 1/4" Hardi board on that, and 12" ceramic tile. Am I ok?

Thanks, Ron

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12-11-2004, 05:14 PM

You can't install the tiling substrate (CBU, membrane, etc.) over the sawn lumber, Ron, gotta be plywood.

You can either remove the hardwood flooring and install plywood (minimum half-inch in your case), or install minimum 3/8ths ply over what you've got.

Eighteen inch joist spacing is a little unusual. Wanna tell us more about the joist sturcutre? Not that we doubt your math or anything. :D

My opinion; worth price charged.

12-11-2004, 06:02 PM
The joists are 1920's rough cut lumber - 2 to 2 1/8" thick 9 5/8" wide, and span 13'9". They vary from 16 to 18" on center, but the 20 Sq feet I want to turn into a half bath has 18" oc under it. I guess before plywood, it didn't matter if you didn't keep things in multiples of four feet.

I think it will not be too much problem to get the 3/4" T&G up. I prefer not to have the added height.


12-11-2004, 06:14 PM
Yeah, I think that's your best bet. And with the plywood you don't wanna hit the joists with the fasteners anywy.

Be sure to screw down the subfloor boards when you get there so they're good and tight before you lay the plywood.