I want to install 4x8 sheets of T&G plywood in my attic for extra storage room, but there are so many different thicknesses. There will be extremely minimal traffic on this floor as I will only be up there once or twice a year and for no more than 30 minutes to an hour at a time.

  • how are you going to get 4x8 sheets into an existing attic? (unless this attic is under construction)
    – peinal
    Feb 21, 2020 at 1:47

2 Answers 2


Always be safe now rather than sorry later. For the small difference is cost, use 3/4 inch sheathing or underlayment. There are several good T&G underlayment brands out there, but T&G may be a little over kill for your application. Simple sheathing, CDX or underlayment should work fine.

  • By underlayment, are you talking about something like 1/4" board that is used for things like vinyl application? I can't find any 3/4" sheathing, but I assume 23/32" would work just as well? Dec 11, 2011 at 15:03
  • in today's market, 23/32 is what we call 3/4 inch. Dec 11, 2011 at 23:26
  • No! not 1/4" vinyl and tile underlayment, I should have said sub-flooring. yes 23/32" Dec 11, 2011 at 23:28
  • I decided to get 23/32" T&G OSB since the T&G cost was not that much more. Plus, T&G just makes me feel better in case I ever decide to further finish my attic in the future. Dec 14, 2011 at 14:35

It depends on the distance between joists or trusses, and the weight of the boxes/items you intend to store there. I personally would not use less than 1/2", and probably at least 5/8".

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