Replacing Diagonal Plank Sub floor for Tile Job

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badali
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Replacing Diagonal Plank Sub floor for Tile Job

Post by badali » Wed Dec 12, 2018 8:26 pm

My home was constructed in the 50s with 3/4" diagonal plank sub floor which I was told is not acceptable for tile.

I've attached a picture of the floor and would like to install tile out until the blue line and as far as the doorway. A section of the sub-floor has already been replaced and my plan is to replace the rest with 3/4" plywood and then use ditra membrane (this will result in a flush floor transition).

The yellow box sits between 2 floor joists (they run vertically from the photo perspective). Can I replace the sub floor up to this box and install the Ditra out over the diagonal plank for the small section (8"x36")?
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Shannon
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Re: Replacing Diagonal Plank Sub floor for Tile Job

Post by Shannon » Wed Dec 12, 2018 10:24 pm

If it was me I would install 3/4" plywood to the bottom side of that area (yellow) screwed and glued ,to make it stronger and then you should be fine. That is as long as the joists are no more than 19.2" O.C.
Anything spaced more then that requires a double layer of plywood or OSB.
If the 3/4" plywood is not tongue and groove then all joints between joists need to be re-inforced as well.
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badali
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Re: Replacing Diagonal Plank Sub floor for Tile Job

Post by badali » Thu Dec 13, 2018 6:41 am

So I cut the diagonal plank out between joists and re-enforce the subfloor from below where it's left hanging?

The floor joists are 16" OC and thanks again for your help!

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Shannon
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Re: Replacing Diagonal Plank Sub floor for Tile Job

Post by Shannon » Thu Dec 13, 2018 8:56 am

Remove all the planks where you can and replace with the 3/4” plywood. Any joints in the plywood that do not fall on joists should be re enforced with some solid blocking below if possible to keep them from flexing with foot traffic.
The shiplap flooring that you can not remove should be re enforced from below as well . I would cut ply wood to fit between the joists and I would glue and screw It to the underside of the shiplap flooring. This would also work to help support the joints in the new plywood if solid blocking is not an option.
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badali
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Re: Replacing Diagonal Plank Sub floor for Tile Job

Post by badali » Thu Dec 20, 2018 7:53 am

Just following up and the combination of blocking and then cut plywood where blocking isn't feasible worked great. The 3/4 plywood boards screwed and glued are almost as rigid as blocking and a massive improvement over the ship lap.

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Shannon
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Re: Replacing Diagonal Plank Sub floor for Tile Job

Post by Shannon » Thu Dec 20, 2018 3:43 pm

Glad things worked out so well.
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