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Fisher252 09-14-2011 11:21 PM

What subfloor materials would be best?
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I am redoing a bathroom, and could use a little advise about the floor. There was a large rotten area around the toilet. The current subfloor is 1x8 planks. I am planning to put in a tiled floor. Size is about 5' x 4'7".

I have attached a drawing showing the situation. The red are the joists. The two wider joists are 4x8 the smaller are 2x8. There is about 1" of joist available on the left side joist to nail onto. The 4x8 on the right is about 1/2" back from the wall. Can I just sister onto that joist and attach subfloor to the sister?

The blue in the picture is the undamaged 1x8's. I am having a hard time finding 1x8, so I figured 1x6 would work fine. I thought about adding double 2x8 blocking, show in green. Half under the tub, half to nail/screw onto. The floor under the tub is fine, and is staying. Is doing this acceptable? Should I forget about the 1x6's and just put down plywood? What thickness of plywood would I need? 2 layers of 3/4"?

Thanks for any help!

ddawg16 09-15-2011 12:43 AM

I bet it doesn't look this bad?

That 'dark' spot is where our shower 'was'.

I understand exactly what your asking.

I ripped out al 10'x14' section of sub floor.

I did my best to cut the existing sub floor 1x6's on the middle of the floor joist. Once I had the new floor joists in, I nailed down new 3/4" struct plywood. I did a good job of edge nailing all of the existing 1x6' retrospect, I think I would have been better off running a second 2x8 sistered up to the joist the existing sub floor was on...and cutting the existing 1x6's flush with the outside of the 2x8. That way the diagnal 1x6's would have the full width of the floor joist...and the new plywood would sit on it's own joist.

For reference....I'm building a 2-story addition now....part of the 1st floor is raised foundation with a subfloor.....I'm using 3/4" T&G glued and nailed. It is also on 2x8 floor joists......but I gotta tell ya.....that gluing sure seems to make the floor a bit more solid as compared to the existing house.

chrisBC 09-15-2011 04:11 AM

Yes doesn't hurt to add blocking wherever suitable.

I would assume that 3/4 plywood will match the thickness of your flooring, I would use this. I would glue to the joists with adhesive and use screws to ensure a tight floor.

I would put down backerboard for the tile, over your subfloor.

md2lgyk 09-15-2011 07:53 AM

I would use Advantech for the subfloor. It is more rigid than plywood, and carries a 50-year warranty against water damage. When I was building my log home, I used scraps of it to make walkways across the yard until I could plant grass. They laid exposed on the ground for nearly two years, and still could've been used for subflooring.

Fisher252 09-15-2011 07:55 AM

So, is it OK to install the blocking as I have shown, and screw the 1x6's to those. The 1x6's will be ending on the blocking.

ddawg16 - it is close to that, just a little smaller area.

gregzoll 09-15-2011 08:41 AM

I used Georgia Pacific's DensSheild for the floor on my bath, when I did it. Put a layer of mud down, laid the densshield, screwed down, taped the joints with mesh tape, then placed a coating of mud to seal the seams and screw heads. From there, laid the tile (16x16) in standard fashion, in a brick pattern.

Snav 09-22-2011 09:31 PM


Originally Posted by Fisher252 (Post 728615)
So, is it OK to install the blocking as I have shown, and screw the 1x6's to those. The 1x6's will be ending on the blocking.

ddawg16 - it is close to that, just a little smaller area.

Did you figure it out by now (it's been a few days) - what did you do?

Like Chris said: yes - add blocking where it's necessary to give adequate support. I'll add that, yes - sistering in a support for your edge is appropriate when necessary.

giants 11-15-2012 06:05 PM

i am tearing old flooring out of bathroom. its good in places rotten in other. what are the BEST sub floor materails to last the longest. do u put down 2 sheets of plywood or osb? is there tarpaper between them? guess im just looking for list of flooring materials.

joecaption 11-15-2012 06:09 PM

Giants, go back and add your own post. To confusing to keep track of to topics at once.

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