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Unread 01-22-2021, 10:50 AM   #56
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Join Date: Jul 2001
Location: Boerne, Texas
Posts: 93,006
I got no eye-dee what might be the difference between your 36-dollar OSB and your 48-dollar OSB, Matt. Either one is over priced to my thinking, but youins Yankees like to spend more dollars for your stuff than we do down here, seems like. Only way to know is to get what information you can about each and look up the specs. Try to find a grade stamp on the sheets. Or possibly get some actual identifying information from those tags.

The sheathing is likely a CD grade plywood and I'd avoid that.

As for two layer subfloor, I like it for tile. Look at it this way, using the Robinson floor tester (ASTM C627) to check for l/360 deflection over 16" joist centers, a nominal 5/8ths" subfloor can be made to pass sometimes; a nominal 3/4" subfloor will pass most of the time; a double layer of nominal 3/4" and 1/2" will pass every time. You are the only one can decide if it's worth the time and expense. It would be for me.

The added layer of subflooring will not improve your joist deflection.

My opinion; worth price charged.

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