Plywood Span Rating 1

[dgengineering]

Hello Everyone.

I'm trying to understand what span rating is for a plywood but I don't get the right hand number. For example, if we have 24/0 or let's say, 32/16 I understand the left hand number means the span between joists across the long direction of the plywood but what is the right hand number? I read somewhere that it is the subfloor span or something but still it's not clear to me. I guess I don't much about subfloors. Can anyone explain with diagrams, if possible? Thank you very much in advance

 

[Heaviside1925]

Hopeful answers your questions.

Link

 

[JAE]

The first number is the recommended span length for roofs.
The second number is the recommended span length for floors.

 

[dgengineering]

So if it's 24/0 it means it's only for the roof? or is it for one story maybe? Thanks

 

[JAE]

I've never used 24/0 but I think you are correct - no span rating for a floor.

 

[lexpatrie]

Only recognized for the roof, sounds right. I'm a bit flustered right now as my cats just got into a huge fight and I had to intervene.

 

[Tmoose]

so you're starting with 3/8" plywood ?

https://www.apawood.org/Data/Sites/1/documents/product-support/rated-sheathing-datasheet.pdf

 

[dgengineering]

also, some thicknesses are not found in the IBC table for some reason. That's something I wanna understand too. Thank you so much for your great answers!

 

[XR250]

Also, I believe span ratings are for 2-span continuous minimum. So when the roofer replaces one bay of sheathing, he should be blocking underneath.