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Unread 04-10-2020, 02:29 PM   #1
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Tile + 1/2" OSB + 1/2 Foam Board + 1/2" Drywall Deflection

Hello Everyone, long time since my last project.

Tiling a room with porcelain and will be hanging a drywall ceiling underneath.

There will be 1/2" Pex Al Pex between the OSB and the Drywall surrounded by the foam board as a spacer.

Will this be OK or is it to close?

For joists that are Unknown wood, but in good condition, 9.25 inches tall, 2.5 inches wide, 16 inches on center, and 15 feet long between supports, the deflection calculated is 0.444 inches.
This translates to a deflection of L / 405.
Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Ceramic tile, Congratulations!

2x10 floor joist will be sistered on both sides with 1/2" OSB.


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Last edited by CNM DESIGN; 04-10-2020 at 03:05 PM. Reason: spelling
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Unread 04-10-2020, 04:22 PM   #2
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The deflection calculator won't give you an accurate number if you sister 1/2" ODB to the sides of your joists. It won't be the same as a solid piece of lumber 2.5" thick. Typical OSB isn't designed to be installed that way.
Jim DeBruycker
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Unread 04-10-2020, 08:38 PM   #3
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Welcome back, Craig.
Originally Posted by Craig
There will be 1/2" Pex Al Pex between the OSB and the Drywall surrounded by the foam board as a spacer.
'Fraid you've lost me completely there. Maybe more hints?

What Jim said. I have no idea what you might actually achieve using that method, but I'm reasonably sure it won't do you much good at all, 'specially considering that none of your pieces of OSB would be longer than 8 feet. Don't think it would be worth any of the effort.

My opinion; worth price charged.

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