Bending strength, plywood versus OSB versus plain timber

Feb 19, 2025 Last reply: 1 year ago 3 Replies

You would have thought this was easy to get information about but all I can find is repetitive waffling telling me what I already know but no actual comparative figures.



I (think I) know as follows:-



Timber is somewhat stronger lengthwise than plywood for bending Plywood is much stronger than timber across the grain OSB is probably similar to plywood (but how close is it?)



I actually found one bit of quantitative information on this:-



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... dated 1952! Has no one bothered since then? :-) The trouble is that it compares 'ordinary wood' with 3-ply plywood which isn't what one tends to get nowadays. I'm specifically interested in comparing 'ordinary' planks with 7-ply plywood (that's 5 + 2 thin veneers) so the above probably isn't very accurate. My (modern) plywood probably isn't so close to ordinary planks but is likely to be similar strength in both directions.



I can find no actual values for the relative strength of OSB (sterling board) compared with plywood or ordinary planks.



What I **really** want to know is how much stronger ordinary timber is than comparable thickness plywood or OSB. It would also be quite good to know how much stiffer it is (not quite the same thing) but that's probably a bit less important.



This doesn't have to be accurate to the n'th degree, but I do want some sort of quantitive indication, like is ordinary wood twice as strong as plywood and OSB, or only 10% stronger, or what? (OK, there's lots of variables but the US Forest Service managed the sort of thing I wanted back in 1952!)


This doesn't compare OSB with ply, but it gives numbers

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probably searching for the various EN31x standards for e.g. WBP would get you numbers to compare?

Searching for 'EN310 Plywood' just provides loads of links to what the test is and how it's done, but none so far giving actual values for plywood being sold. I'll keep looking though, I might find some actual values down there somewhere!

Thanks!

Finally found this:-

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This looks like fairly middle-of-the-range sort of plywood so it gives me some idea when compared with the ones for OSB above. The different types of OSB vary quite a lot!

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