Is it adviseable to lay floor tile directly on 3/4″ OSB without an underlay?
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Probably not a good idea. Is the total floor thickness only 3/4"? That's too thin. And the floor joists ... what size, what spacing, and what span.
Generally, the floor should be more than an inch thick. In your case, adding a layer of 1/2" underlayment grade ply might be sufficient.
I'm sorry, I thought you wanted it done the right way.
Thanks for the input Ed. The joists are 16" floor truss joists on 16" ctrs. and a 15' span with hot water radiant heat in the floor. This is a new manufactured (built off site) home and the floor certainly seems sturdy. There is some discussion with the owner about to underlay or not to underlay. I have suggested hardibacker or wonderboard which is what I would do if I had drawn the permit on my license. Others have said (Naw you don't need that). Just looking for some information for the owner.
Thanks again,
markm123
You have not said what kind of tile, but generally speaking, I would say definitely not.
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The hardie or wonderboard is not going to give you any more strength. Anyway, the hardie needs to be screwed down ... how would you do that without hitting the radiant tubes?
I'm sorry, I thought you wanted it done the right way.
I'm trying to figure out how he got in floor radiant in the sub-floor? but has no underlayment or self leveler??
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
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It may be under the subfloor... a 'staple-up' installation.
yeah, I found out it is in an email.I Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
Mark:The Tile Council of America would tend to disagree with most of your responses. See method F148 in the TCA handbook... 'Single layer plywood (or OSB) subfloor for joist spacing UP TO 19.3" IS acceptable to tile over', provided:*Floor deflection is limited to the standard 1/360 of the span (your truss system w/ 3/4" glued subfloor was engineered for a min. 1/360 def., and is 16" o.c.)*You use an uncoupling system over the subfloor (Like DITRA)*You use a latex modified thinset (Like TEC FullFlex or SuperFlex)Like your situation, I've had to tile over radiant flooring where screwing down tile backer was..a hazard...DITRA lays directly over an OSB subfloor, uncouples the tile and actually stiffens the floor. Ditra is a felt-backed, stiff polyethylene sheet (comes in a roll) impregnated w/ dove-tailed indentations which lock the tile and thinset into, essentially, one big floating tile pad which is UNCOUPLED from the subfloor. Ditra also waterproofs the floor, so it's good for wet environments. Check out the Schluter website for specs on Ditra. TCA approves it. It's easy and fast. It's a great solution to this type of problem. Ditra. Try it. You'll like it. So will your customer.
The Ditra is a good product, and it solves many installation problems. But, I question that it stiffens the floor. How does it do that?
And I'm curious ... is there an on-line calc for determining the floor stiffness? I have one for 2x joists, but it specifically says not to use it with engineered joists.
I'm sorry, I thought you wanted it done the right way.
Well, I suppose the Ditra/mortar/tile monolith just sort of spreads the load more evenly..(sort of like bridging between floor joists stiffens a floor). It creates a diaphragm. However it does it, I can tell you from experience it does. My Ditra floors felt like solid bedrock when they were cured.Anyhow, I doubt the floor you describe needs any stiffening. Just use the Ditra and be done with it.
no
You need a minimum of 1 1/8 to 1 1/4" plus there are issues with joist size and spacing.
Look for the TCA hand book. Tile Council of America.
Ask here too.
http://johnbridge.com/vbulletin/index.php
Eric
I Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]