Plywood for flooring

[JSukowaty]

I came about some 3/8" exterior plywood and would like to use as much as I can on my cabin project.  I don't have any problem using it for exterior under siding, but what about flooring?  How much support would I need to use 3/8", or should I just skip using this on the floor?  I also have plans for a loft, would this work for that?  How about the roof, what kind of support would this need for under steel roofing?

Thanks for all your help, I am sure I will get plenty of replies with useful information here.

[glenn kangiser]

   Not heavy enough for flooring - extra framing for acceptable stiffness would eat up any savings.

Floors are usually minimum 3/4 thickness.

[JSukowaty]

Thanks for the confirmation.

I was afraid of that.  Well, I should be able to use it for outside and inside walls and roof though, right?

2x6's at 20" center for the roof, 3/8" plywood with sheet metal over it?

[glenn kangiser]

I think that should work.  The roofing will support itself to about 4 foot centers if on purlins so the 3/8 could still make pretty good sheathing and a bit of diaphragm bracing.  Note that this is just an opinion - I'm not an engineer or architect.  I assume you have no codes to meet.

[JSukowaty]

So far there haven't been any codes brought up, but I will check into that.  I really like this site, it has given me motivation to get my project completed.

Thanks again!

[glenn kangiser]

No problem -- possibly if it is a project in progress you don't want to ask. Glad you enjoy the forum.

[NorthernMich]

why not 3/8 plywood with grain going one way, a second layer using a 90 degree grain layout=3/4" total with stronger grain strength..?!

Earl

[John Raabe]

Earl's idea of doubling up might be the best use of 3/8" material. For it to work as well as 3/4" however, it needs to be glued well - as well as in a 3/4" panel  .

I wonder about that 20" spacing on rafters. It doesn't seem to work well with 4'x 8' panels and their 48" primary dimension. 48/16=3, 48/24=2. This is why rafters, joists and studs are always either 24" or 16" o/c. Anything else ends up with lots of waste.

[glenn kangiser]

I was wondering about that too, then thought it was existing, but reading it over again, maybe it's planned, not existing -in which case I agree with you.