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02-29-2008, 04:19 PM
I am laying tile in my sister's bathroom this weekend. The house is very old. When I inspected the floor, it looks like a subfloor of undetermined thickness lying accross the joists. On top of that is 1/4 in plywood. There appears to be a loose board or two under the ply near the wall. Am I correct in assuming that the plywood has to go? What thickness of ply would you put down? I was thinking 2 sheets of 1/2 inch, but should we go thicker on the first sheet? Thanks!


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02-29-2008, 04:27 PM
Hi Lisa,:)

You're correct about the 1/4" - it has to go. It's nigh impossible to fasten anything less than 3/8" properly with screws.

It's hard to answer the rest of your question until we know more about what's under that layer of ply. Also, you should run the joist information through the Deflecto (http://www.johnbridge.com/vbulletin/deflecto.pl) . Let us know what you find.

02-29-2008, 04:41 PM
The joists appear to b 10"X1.5" 16" OC and 13 ft long. The bathroom is 9X5. The subfloor is 3/4 in planks, not T&G. Thanks! The deflection calculator shows it is rated for tile (assuming my measurments are correct!)

02-29-2008, 04:57 PM
If height permits, I would put 5/8" exterior BC ply over the planks, then a 1/4" cement board.