can include a layer of rigid insulation under tile floor?
I’m installing tile on a 3′ x 5′ area under the interior side of an exterior door in a bedroom – yep – the bedroom has a door to the outside. The rest of the bedroom floor is 3/4″ oak which has already been installed and finished. The tile floor, when finished, will sit just shy of the oak floor by about 1/4″ to 1/2″.
The customer would appreciate even 1/2″ piece of polyiso on top of the concrete slab so that the slab doesn’t telegraph cold into the room where people will be walking around in socks or even bare feet. We have 1 7/8″ to play with so I was figuring on 1/2″ of polyiso for a thermal break followed by 1/2″ of plywood and then 1/4″ hardie tile backerboard followed by 3/8″+ slate tile and thinset. TOtal would keep me just under 1 7/8″. OR, maybe the 1/2″ of ply wouldn’t provide enough stiffness so I could install 3/4″ ply and skip the tile backerboard?
My question is, will this small section of tile be stable? Could I finish the perimeter/junction of tile and oak with a silicone caulk instead of grout?
Grateful for any suggestions.
Thanks,
Don
Replies
It is a small area, which minimizes flexing, but putting the foam under tile, with just 1/2" plywood, could cause grout cracking, possibly even tile cracking over time as the foam became more and more compressed with use. Or not, I don't know. I've never seen it done.
Why not install an electric heating mat instead?
wouldn't the slab try to suck the heat out of the mat into the whole slab thus either negating the impact to some extent and costing a fortune? I think would especially be the case if the slab is attached directly to an uninsulated foundation. I would think any amount of foam would be a help. My coffee cup is only 1/8 thick and I don't burn my hand when I pick it up. Maybe go with the thinest foam witht the 3/4 ply.
1/4" ply, 1/4" Wedi board
1/4" ply, 1/4" Wedi board Electric Radiant (optional), Tile........S&P To Taste
the shower pan for the kerdi shower system is a type of styrofoam ,i have used it in showers and never had a problem. the curb is also foam
when you look at it its hard to beleive you can lay tile over it but it is a proven product . and there is no hard surface between the foam and tile only kerdi membrane
i think if you lay the foam in thinset using a 3/8 notched trowel so there is no voids under it , it could work. use non modified thinset under the foam
good luck........nicko
why thinset? help?
nicko you say "non modified thinset under the foam"
the word NON catches my attention...
woooootttaooo... I'm in trouble,
Why "NON" modified, my thought was latex modified would be better....
I think i did it with superflex thinset under the foam and on top of the foam(under the tile)... one job down and I was going to do another the same way... is the superflex going to get me in trouble???
"Modified" has latex
"Modified" has latex ingredients that require drying. When sandwiched between impermiable layers, the ingrediants cannot dry.
That is why you use NON modified there. It cures instead of drying though chemical process.
Find a WEDI dealer in your area. It's a foam panel of various thickness with cement on both faces, it was made as an underlayment.
Is that generally true for insulation foam? That is, could you lay 12" ceramic tile in thinset on stryofoam?
Has anyone done this? The DOW people say the foam will withstand 15#/square inch, (2160 lb/sf) which is plenty of strength, but is it rigid enough to prevent cracks in the grout?
Thanks!!
Both WEDI and Shulter make XPS foam core tile backer board. Do a search on them to see about crack complaints. I've not had problems, but I also used epoxy grout which is much stronger and more flexible.
Paul
I'll agree epoxy grout is "stronger", less permiable and maybe more dense than regular grout, the more flexible? Really?
I'd be willing to recant that now.
I set up a test of epoxy grout YEARS ago when I did my bathroom. I took two tiles and grouted them with a 3/16" gap over a piece of wax paper. The only thing holding them togeter was the grouts bond with the edges of each tile piece.
It's been shuffled around my garage over the past few years (it might be 4 years old now). I seemed to recall getting some flex out of that seam in the early days, like a couple degrees.
I just went out to verify and whiletrying to bend the seam, with a significan amount of pressure on the seam from my thumbs, I managed to break the two pieces apart again. The grout did take some of the edge from one of the tile pieces with it however!
While I thought there was flex in that joint, I can't be sure of that now so I recant that.