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I am building a new house in central Florida and have had many discussions involving the new roof. Due to the Hurricane activity people are looking for safer roofs and leakage. 1 effect has been the use of waterproof tape on all the joints, but another discussion involves the plywood thickness. Does anyone have a preference or reason for using 5/8" over 1/2" sheathing and why? Thanks,
MoW
 

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My builder friends tell me that 5/8 is easier to install over 2 ft o.c. because you don't have to us clips. The deck will be smoother and able to handle more weight. Down side is the expense and heavier weight of handling of the sheathing. I would think that there is more wood for the nail to anchor as well.
Jan
 

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We here at the State of Illinois require 5/8" and no C-C sheets. We don't want voids. 5/8" hold nails MUCH better. We try to look at the long term picture. There shouldn't be sag years down the road. One of my biggest pet peeves is a new costruction roof where I can pick out the location of every single sheet of plywood(probably OSB).
 

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I put 1/2" CDX on most houses. I never use OSB. If it was my house I'd probably put 5/8 or even 3/4 CDX.

If you don't use clips please make sure there is a 1/8" gap between each piece of plywood. Usually just dripping a nail between is good enough. If you don't leave this space expect warping of the wood and buckling of your roof.
 

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That Amazing i dont know of one builder here in minnesota that uses 5/8 for roof decking most use 7/16 OSB and have seen a few who use 3/8 cdx. 7/16 is adequate but you dont want to have to many people or shingles in one spot. 3/8 is insane walking truss to truss. Have never had a problem with 7/16 or 1/2 inch OSB as far as sagging in 15 years. We use plywood for setting up protecting the winows on houses. leave a piece of 1/2 inch cdx and a piece of 1/2 inch OSB out in the weather for a couple a months the cdx will warp and separate. the OSB will swell up only. CDX is stronger but OSB Holds up better as far as moisture goes.

I use 3/4 OSB on anything under a 3 pitch for snow loads.
 
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