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Old 06-06-2010, 05:45 PM   #16
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Subfloor thickness


Inge--

3/4 cdx tongue and groove plywood has been the standard for the last 35 years(in the u.s. any way.)

Two layers of that will do the job. Top that with a tile backer like Durrock set in thinset and you are set.

I may have used the wrong name for that Schluter product--They make fine products but I don't use them my self. sorry.

Your floor Joists are to light for safe tile installation. I think that you should add more joists of the same size. I know that is a lot of work.--If you don't beef up the joists you take the risk of tile failure.

--Good luck--Mike--

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Old 06-06-2010, 06:46 PM   #17
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CDX (t&g) is OK for a SUBFLOOR. CDX IS NOT OK for an UNDERLAYMENT over a subfloor and under tile. A second layer of plywood would be an improvement but........

A second layer of subfloor plywood WILL NOT necessarily improve the deflection of the floor structure.
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Old 06-06-2010, 08:02 PM   #18
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Subfloor thickness


Here is something new. I just remembered there is a false wall down below this that comes out 3' on the joists. It is not a great support but does add some support. I forgot about this as I don't think it is a great support but like I said it does add some.
The other issue is I wonder if you guys think my tile job will be big. If you call a 4' strip between the cupboards big then yes. Most of the tile will be about a 4' strip. Other parts will be a 6x4 section and another 6x4 section. It is not a big kitchen at all.
My kitchen is only 8' wide. The rest of the span goes into another room on the other side of a wall.
Could I post a picture to show you my kitchen?
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Old 06-08-2010, 11:55 PM   #19
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I ended up taking out the crappy 1/2" plywood and have replace it with some nice 3/4"stuff. It has nine layers and both sides are usable. I told them I wanted the strongest stuff they had and they sold it to me. What next? Radiant, thinset, ditra, thinset, and then tile? Or 1/2" ply and then radiant, thinset, ditra, and then thinset and tile? Anyone?
I also sistered the joists and most of them I got about 70% of the joist sistered. Some were more than 80% and some were less than70%.
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Old 06-10-2010, 09:06 PM   #20
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Subfloor thickness


This thread has info re: subfloor/underlayment; floor strength; tiling
Considering replacing playwood subfloor, many questions.
There are many threads on here discussing the relevant factors; it's well worth digging through them. johnbridge.com also has useful information pertaining to tiling, ditra, etc.
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Old 06-10-2010, 10:12 PM   #21
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My best tile installer would say to use 1/2" exterior grade plywood, radiant heat, then tile. He hasn't had a failure in 40 years, so take it or leave it!

Tia
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Old 06-10-2010, 10:18 PM   #22
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1/2 on top of 3/4 right?
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Old 06-10-2010, 10:27 PM   #23
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Originally Posted by ingeborgdot View Post
1/2 on top of 3/4 right?
Yes, to equal the 1-1/4" standard. Both mortar and screw the plywood to the base floor. As far as the issues with your joists are concerned, you probably don't have as much of an issue for such a small area as there would be for a large expanse, so long as it is solid. Running the length or perependicular doesn't really apply for tile, since it doesn't expand and contract like solid hardwood, for example.

Tia
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Old 06-10-2010, 10:43 PM   #24
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Would I not use ditra?
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Old 06-10-2010, 11:10 PM   #25
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Originally Posted by ingeborgdot View Post
Would I not use ditra?
Not necessary, Ditra is for situations where you don't have room to build up. It's a stabilizer when there is no option to increase floor height.

Tia
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Old 06-10-2010, 11:22 PM   #26
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So you are saying with my joists, that I now sistered I could have 3/4, 1/2 and then just put my wire over that with thinset?
Would cement board be good to use under the wire?
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Old 06-10-2010, 11:34 PM   #27
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Originally Posted by ingeborgdot View Post
So you are saying with my joists, that I now sistered I could have 3/4, 1/2 and then just put my wire over that with thinset?
Would cement board be good to use under the wire?
Cement board, exterior-grade plywood, both fine. Then you can go over with the radiant and tile. I don't understand this "sistered" thing.

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Old 06-10-2010, 11:43 PM   #28
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It is where you glue and screw another joist to the original joist as long as you can make it to help give it more support.
Would I put the cement board on top of the 1/2 or leave off the 1/2 and put on the cement board? Sorry for all the questions but just picking the pro's brains to get as much info as possible. Thanks for all the help though.
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Old 06-10-2010, 11:52 PM   #29
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The Flooringgirl says..... "My best tile installer would say to use 1/2" exterior grade plywood, radiant heat, then tile. He hasn't had a failure in 40 years, so take it or leave it!"

And...... "Both mortar and screw the plywood to the base floor."

Oh boy.......

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Old 06-11-2010, 12:08 AM   #30
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Any your point is?

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