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#1 |
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mjay
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Floating Membrane Under Tile
Installing tile over 3/4' cdx. Always used 15lb felt - wire mesh - mud - tile. Floor is solid {2*10' 16o.c 8" span}. Don't expect movement, but always willing to try new stuff if it gives me less chance of call-back, and this new membrane looks good stuff.
Any input/experience/advice is welcome. Tile store is recommending cement board for floor. Any input/experience/advice is welcome. Also installing electric radient heat pads - Any input/experience/advice is welcome. There's some top class people on this forum,........and then there's me
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#2 |
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R&D Tile
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Re: Floating Membrane Under Tile
CDX isn't an acceptable grade of plywood for under tile, if you have to leave it, the only wat I would do this, is a full mud job with roofing felt and wire lath, mud 1 1/4" thick.
![]() Nothing out there can beat a mud job. ![]() You can probably also get away with another layer of 3/4" ext.grade AC or BC over it, then a CBU or membrane of choice. ![]() 3/4" is bare minimum for a subfloor for tile, wood between the joists addresses the flex there, the joists themselves determine the overall flex in the whole floor, your fine there.
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#3 |
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Floorwizard
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Re: Floating Membrane Under Tile
Actually the bare minimum is 1 1/18. That is IF your using the correct plywood.
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#4 |
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R&D Tile
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Re: Floating Membrane Under Tile
That has been an on going debate for a awhile now now, as to what makes up that height, all CBU manufacturers warrantee there CBUs over 3/4" ply as does Ditra, but they say to use 1/2" cementboard, even though it adds no strength to a subfloor, 1/4" is for floors and can be used instead, I personally won't tile over a single layer wood floor and give a guarantee.
![]() That is for 16" joist spacing, anything wider has to have 2 layers of wood, the top layer being sheet plywood or OSB, same as single layer floors, yuo can only go over plank flooring with a mud job, CBUs must be installed over Plywood or OSB, same with membranes. ![]() Hope this helps.
Last edited by R&D Tile; 02-08-2006 at 08:16 PM. |
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#5 |
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mjay
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Re: Floating Membrane Under Tile
Thanks for the prompt replies. Yes, there are a lot of opinions on materials and methods.
It's good to hear healthy debate. Still looking for opinions on the membrane applications, and electric radient heat pads. |
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#6 |
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Floorwizard
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Re: Floating Membrane Under Tile
I love debates. I always learn a thing or 2.
I was using the T.C.A. as my guide. But I would break from their rules in my own home in some cases. |
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#7 | |
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R&D Tile
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Re: Floating Membrane Under TileQuote:
![]() Still wouldn't do it though, more is better.
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#8 |
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Floorwizard
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Re: Floating Membrane Under Tile
I will have to check at work.
What page? |
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#9 |
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Tom R
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Re: Floating Membrane Under Tile
Don't know where it's written (besides in my head), - - but it was always 'minimum' of 1 1/4" built-up wood for under tile, - - as of about 10 years ago it conveniently (for contractors?) got changed to 1 1/8", - - I still stick to the 1 1/4".
I would think that anything stating 3/4" is either a mis-print or a mis-understanding. Think about it. I guess it's 'possible' someone is stating you could use 3/4" plywood as long as (and only as long as) you ALSO were adding 1/2" CBU. Last edited by Tom R; 02-08-2006 at 11:25 PM. |
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#10 | |
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Mike Finley
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Re: Floating Membrane Under TileQuote:
1/4 hardi, electric heat then tile, as always I would be using FlexBond thinset. or Ditra, electric heat, then tile. You said the floor has no flex right? |
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#11 | |
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R&D Tile
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Re: Floating Membrane Under TileQuote:
![]() Ditra can be used over 3/4" OSB or plywood & CBUs DON'T add any strength to a subfloor, more plywood does, Hardie says it's 1/4" CBU can be used over 5/8" minimum sheet plywood, in other words that 1 1/4" means nothing, it's what's under the CBU or a membrane that counts first. ![]() Remember, you first have to meet the strength in the joist system, L/360 for ceramic & L/720 for stone, the joist system dictates the overall flex in the floor, plank flooring and sheet products only help strengthen the flex in a floor between the joists. ![]() All of that said, as long as the joists system is fine, I always add a layer of 1/2" plywood over all single layer subfloors, before adding a CBU or Menbrane, unless, doing a full mud job.
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#12 | |
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R&D Tile
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Re: Floating Membrane Under TileQuote:
![]() As said above, someone who reads the 1 1/4" minimum thinks their floor might be stronger, but it's not, unless that is all wood and not CBUs in the mix, hope this makes sense.
Last edited by R&D Tile; 02-09-2006 at 07:05 AM. |
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#13 | |
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firemike
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Re: Floating Membrane Under TileQuote:
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#14 |
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Floorwizard
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Re: Floating Membrane Under Tile
R&D,
I hear what you are saying. Sounds like you know what your talking about. There is a paver question I would like to hear your thoughts on. It has just been posted. |
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#15 | |
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R&D Tile
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Re: Floating Membrane Under TileQuote:
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#16 |
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mjay
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Re: Floating Membrane Under Tile
O.K. It will take me a moment to digest all that. But, Does everybody agree to 'No, to CDX'.
I have installed an 'Uber' OSB in other homes, (used as a finished floor) and was very impressed with the quality of the material.Before people shout Noooooo to an OSB sheathing the specs are impressive - Panel deflection 0,106 inch at 330psf. at 24" o.c. Thickness Swelling 3.5% after submersion for 24hrs. MOE 250psi [load required between two joists for deflection] MOR 7psi Comes with 50 year warranty. I'm looking for further info from company for suitabilty for this application, and researching the reasons to add another layer of sheathing to the floor. This is the ground floor with 2*10" - 16" o.c. 8' spans sitting on masonary walls, I haven't done the math but I'm confident it surpasses the L-720 (and yes i will do the math to be sure). Someone, mentioned Ditra and any tips or advice would be helpful. I understand the radient pads go under the Ditra. Tile is not my speciality, and I appreciate all your opinions. Last edited by mjay; 02-09-2006 at 04:15 PM. |
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#17 |
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Bill_Vincent
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Re: Floating Membrane Under Tile
Over 3/4" subfloors, just about ALL manufacturers will warranty even 1/4" CBU. Over 5/8" subfloors, then it has to be 1/2".
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#18 | |
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Tom R
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Re: Floating Membrane Under TileQuote:
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#19 | |
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R&D Tile
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Re: Floating Membrane Under TileQuote:
CDX is the lowest grade of ext. grade plywood there is, if you even want to call it ext. grade, too many voids and rough, use AC or BC grade for subfloors getting tiled.
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#20 |
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Floorwizard
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Re: Floating Membrane Under Tile
Never CDX is my 2 cents.
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