Subfloor Over Sub + Rad Tube Heat [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


View Full Version : Subfloor Over Sub + Rad Tube Heat

05-29-2009, 08:52 AM
This is a 100 yr house. Joists 19, then 1x6 horizontal, not diag. Heating guy laid 3/4 osb screwed on top of that. then laid 1/8 insul., then 3/4 x 8" 8ft boards gapped at 8" for 3/4" tubing. then put 1/2" osb on top of that. so heres my question. customer wants it tiled. what are my options? remove the 1/2" osb put 3/4" ext plywood then ditra, or remove 1/2" osb put 3/4" osb then ditra? or will rock do instead of ditra. what are the limitations of osb as subfloor compared to ext 3/4 plywood? i know for stone i need two 3/4" and rock/ditra. look how high that would be!! tx

Sponsored Links

05-29-2009, 10:21 AM
Welcome, Walleyes. Please put a first name in a permanent signature line for us to use. :)

And if you're in the tile trades, add a bit of bio information in your User Profile so's folks can see who they're talkin' with, eh? :)

The part of that sandwich that would bother me most is the eighth-insulation. Tough to tell what that might be and how much movement it would introduce. The half-inch OSB over the eight-inch strips might be adequate with gaps of only three-quarter-inch between'em. You'll not find any industry standard to cover the installation, but with Ditra or similar on top (you ain't gonna wanna try to use any mechanical fasteners, eh?) you might get by.

That all presumes that "heating guy" installed the various layers in the correct orientation and using correct fastening methods, of course.

But that eighth-inch of "insul" might jinx the whole deal for moi. :shades:

My opinion; worth price charged.

05-29-2009, 10:30 AM
The 1/8" insulation is strange to me too..never seen that before and we go over lots of radiant floors. I hate these hybred installs where lumber sleepers and multiple layers are used in odd configurations. Too many materials to move and cause problems. I love Gyp or mud over the pipes..but thats another topic.
I would also second the "no faster" idea..Been there and got the "hole in the pipe" t-shirt and it's a spendy one to be sure.:jack:
If it were mine to tile over I'd go over the OSB with Ditra. I'd be sure and use a good modified thinset to stick the ditra down to the OSB and them go with a high quality unmodified to set the tile over the Ditra.