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Subfloor Opinions

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Old 11-26-2018, 12:21 PM   #1
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Subfloor Opinions

So I ripped up the old diagonal floor boards in the bathroom (1950s ranch), mainly because it will be easier to work with plumbing that needs moved around. We extended the bathroom out a little but ran into the floor being in between joists.

Here's a pic of my situation, I have ductwork in the way that doesnt give me much room to add on anything.

I was thinking maybe 2x4s cross ways with joist hangers to help support the existing floor wall and new sub floor.

Also bought 3/4" plywood for the subfloor and was gonna add either 1/4" or 1/2" cement board for the travertine tile. This suitable? Joists are 16 center.
My only dilemma with adding another sheet of plywood is the 3/4" plywood 1/2" cement board, thinset, and the tile already puts the height of my floor over the edge of the hardwood floors, if I add another sheet of plywood I feel its gonna be well over.
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Old 11-26-2018, 02:35 PM   #2
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Re: Subfloor Opinions

Oh my!

Why not 1" ply and Ditra? (With Kerdi band it will be waterproof.) Even then not sure you are going to get enough for travertine. Blocking...lots of blocking. Sister every joist you can. Those are 2x6" joists right? Span? Run it thru the load calculator I posted below.

Forget Hardi etc. Learn to work with Schluter Systems for all bathroom tiling, including showers. Go watch Youtube vids.

Use this! The John Bridge forum is an excellent helpful forum even for happy home owners.


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Old 11-26-2018, 02:36 PM   #3
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Re: Subfloor Opinions

Did you build the wall on top of the wood floor? The wall should be sitting on the subfloor and a space for expansion given for the wood floor.

2x4 and hangers should be sufficient. I wouldn't install travertine on a floor. It's too dang soft and porous. They need to get porcelain that looks like travertine. I would use Ditra instead of cement board, but that is a personal preference.
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Old 11-26-2018, 02:40 PM   #4
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Re: Subfloor Opinions

I was trying to meet the existing hardwood or atleast get close but now I'm thinking just do the 3/4" plywood I have and add another 1/2" over top offsetting seems then another 1/4" cement board over that. I did do the calculator before but was confused on the joist length part. Do I measure from one end of the house to the other because I think it's one long joist.

The joists in there are 2x10 (9.5)
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Old 11-26-2018, 02:45 PM   #5
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Re: Subfloor Opinions

Yeah we put the 2x4 before cutting out the floor, either way we were gonna be in the middle of the joists. Cant go out further to the other joist and in any further would mess up design plans for shower fitting in, vanity, toilet etc.

So yeah I was thinking just fasten the 2x4s in between the exposed joist and the other joist hidden further back under that 2x4 with the hangers for extra support.

We already bought our floor which we got a great deal on, like $2.99 sf instead of about $11.99
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Old 12-02-2018, 05:21 PM   #6
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Re: Subfloor Opinions

Would 3/4" rtd plywood work for subfloor and 1/2" bcx work on top?

Or should I get the 3/4" osb?

Was also told blanke permat could take the place of the 1/2" underlayment, so just the 3/4" and blanke permat would work?
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Old 12-02-2018, 05:34 PM   #7
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Re: Subfloor Opinions

been awhile since I looked at the chart, but iirc stone (travertine) requires a stiffer subfloor so using a 3/4" + 5/8" may be necessary. I would use Ditra or an equivalent uncoupling membrane over top of the plywood. Hardi doesn't increase the rigidity of the floor system.

you can use the cheaper osb underneath but I always use either plywood or
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Old 12-02-2018, 07:47 PM   #8
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Re: Subfloor Opinions

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