3/8” Plywood on 24” Raftors - Help

Hello, I am currently getting estimates to put an new roof on my home. I’m getting some conflicting information. I’ve confirmed I have 3/8 on 24 inch raftors. I’ve had some contractors say it needs replaced with 1/2 or 5/8 and some say it can stay at 3/8??Some say 3/8 isn’t to code anymore. I really don’t want to pay for all new plywood because I may be moving within a couple years. I know I will need a few new sheets at least due to rotting. I live in Ohio if it matters. Thanks!

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3/8" is not to code. Code states 5/8" for 24" rafter spacing. You can look it up online for free. Section R803. Chapter 8 of IRC Code Book.


Thanks. So if I need a few sheets to replace bad ones, they will have to put down 5/8? That’ll be a mismatch with the remaining 3/8.

If you’re okay with violating code, they can just replace the existing with 5/8". You’re only talking 1/4" difference. If you’re using laminated dimensional shingles, hardly noticeable. However, if you’re interested in complying with code, you need a complete redeck. If this happens to be an insurance job and your policy has ordinance & law coverage, the insurance should pay for it. I personally or professionally wouldn’t replace a roof and keep 3/8" decking.

In my area 3/8ply on 24" trusses is still code and common
An hour north of me they have to use 1/2"
Check with your local codes.

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“You may be moving in a couple years”. Are you willing to gamble on a home inspector not finding the sheathing issue? You may end up paying twice for a roof with the resheath on the next go around. I can feel 3/8” when I walk it.

Honestly didn’t think about that and it’s a valid point. Tough paying for all that wood when it’s mostly in good condition. Is there no grandfathered rule when it comes to these residential codes?

If you have old 3/8" decking on 24" centers it should be sagging between the trusses.

3/8" sheeting shouldn’t be allowed to begin with even over 16" centers, it is just too thin.

IMO 1/2" is too thin for 24" centers also.

If you want a decent roof the 3/8" sheeting should be removed and discarded and replaced with 1/2" or better plywood or OSB.

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I don’t like 3/8 decking anymore then the rest of the guys. On 24 inch centers it feels like you’re walking on eggshells. With all that said go in the attic and check the APA stamp for span. It will show 24/16. When your home was constructed 3/8 decking was rated on 16 inch Center and 24 inch centers. As far as I know it’s still carries that same rating today. I personally would not put that size decking on a home.

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