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Unread 02-07-2022, 06:07 PM   #1
garch
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You have never failed me before...

I have remodeled a couple of bathrooms with this community's help. You have never let me down. So, here is my question.

I am getting ready to tile the bathroom floor using Blanke Permat. I have floor trusses are on 24" centers. To be clear, these are not I joists made of wood. The 3/4" OSB is attached to the top of the truss which is a 2 x 4. Edge to edge of the truss top is 20.5".

I can see a bit of flex in the floor where the large whirlpool valves came through the subfloor. I will replace the osb that need to be patched before applying the permat. I am using 12 x 24 porcelain tile. Should I put down 1/2 osb or ply on top of the 3/4" before the permat?

Thanks in advance!
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Unread 02-07-2022, 06:27 PM   #2
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First time for everything, Gregg.

I'm not familiar with Blanke's instructions, but I would not tile that floor using any known tile substrate without I first installed a second layer of minimum nominal half-inch exterior glue plywood with no face of grade lower than C.

My opinion; worth price charged.
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Unread 02-07-2022, 06:48 PM   #3
garch
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Ok, 1/2" exterior plywood it is....thanks!
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Unread 02-10-2022, 07:01 PM   #4
garch
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You have never failed me before...

Rough plumbing is complete. Bought the 1/2" exterior plywood. I have patched the 3/4 plywood. The bathroom is on the second floor and the walls were built upon the floor. So I cannot hit the flat top (3.5") of the floor truss on either side of the room with the new 1/2" plywood.

Do I need to put blocking on the edge of the room under the current subfloor (parallel with the trusses) on both sides? Or can I just but it next to the bottom plate of the walls. I plan on installing the 1/2" 90 degrees to the current floor.

Should I glue and screw this floor, or just screw?

Thanks in advance!
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Unread 02-10-2022, 07:27 PM   #5
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Gregg, if you orient your second layer of plywood subflooring parallel to the joists, you may as well just not bother. Seriously. For that second layer of subflooring to provide additional structure, which I think you need, it must be oriented with the strength axis perpendicular to the joists.

You'll be fastening the second layer only to the first layer, not the joists, and only with mechanical fasteners. I'd leave a 1/4" gap all around.

My opinion; worth price charged.
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Unread 02-10-2022, 08:06 PM   #6
garch
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You have never failed me before...

Thanks CX!

Just to clear, my trusses (joists) are running north and south. The current sub (4 ft dimension) floor is running east and west. And your advise (which I am very grateful for) is run them the same way, a 1/4 from the edge, correct?


Thanks in advance!
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Unread 02-10-2022, 09:26 PM   #7
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Let's be clear. The strength axis of the subflooring must be perpendicular to the joists. That is usually the 8-foot direction of a 4x8-foot sheet of exterior glue plywoods. Doesn't matter how long the piece is, it matters what the orientation of the plies in the piece is. Could be a 4-foot piece you're working with, but it must be a 4-foot piece cut from the 8-foot direction of the panel. The face grain must be perpendicular to the joists.

We're on same page?
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Unread 02-11-2022, 06:05 AM   #8
garch
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Thanks CX

We're 100% on the same page and I always feel better knowing that I am doing things the right way.

If you are ever in Detroit, I'd love to buy you a beer!
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Unread 02-11-2022, 08:13 AM   #9
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It would be helpful to put that geographic location into your User Profile so it appears with each post, Gregg. Often helpful in answering some types of question. 'Specially questions such as, "Do I wanna have a beer with this guy," eh?
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Unread 02-11-2022, 05:06 PM   #10
garch
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I have updated my location, lets see if this works!
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