Interesting flooring dilemma - DIY Chatroom

ply · 09-23-2009, 01:41 PM

I have a tiling dilemma that needs a little background info, so please bare with me a second while I set the stage.

I'm in the process of gutting a house that was built in the late 70's with electric in ceiling radiant heat. Records with the electric company showed monthly bills peaking at $600+ which caused a previous owner to supplement with a boiler and water baseboards. The problem with this is the house wasn't built with baseboards in mind and many rooms were not suitable for that type of heating. The master bathroom being one of them. I have since converted the downstairs to in-floor radiant heat. (Slab on grade with 1.5" lightweight concrete pour). However, the master bath is upstairs and I can't use the same installation. I decided to pull up the sub-floor and install the tubing underneath (kind of like a staple up, but did not want to tear out the kitchen ceiling). I had in my head that I would put the sub-floor back together, then put down 1/4" or 1/2" wonderboard for stiffness as well as mass to conduct heat, then tile over that with 20"x20" tiles. However, I failed to consider the good odds of nicking a tube with a screw since the tubing is in direct contact with the sub-floor

I considered putting down more plywood, but would rather not since wood is a poor conductor of heat. I could use 1" corrosion resistant screws, but the manufacturer calls for 1.25".

Could I use 1.25" screws for along the joists, then use 1" for the rest of the pattern?

Does anyone have any other ideas?

Thanks in advance to any and all input,

Mike

rusty baker · 09-23-2009, 04:26 PM

Screws that go all the way thru the subfloor will have less holding power than screws that go 3/4 thru. So there is no reason to use screws that will hit the tubing.