I've seen all kinds of places on the web say to run your boards perpendicular to floor joists, but it never gives a reason. So, what is the reason? I've also seen that if you do run parallel, you have to add more subfloor - again why? What if you want to run parallel but you don't want to add subfloor - is there another way to properly install?

TIA

Rookie

OK, I found the search button and Gary has quite a bit of helpful knowledge. Deflection is the answer...

I also found someone posted about 24 on center and 3/4 OSB. I'm in the same situation. So, I'm wondering - if I got in the crawl and added 2x6 blocks running perpendicular to the joists every 16 on center, and then screwed the existing floor to the new blocks - would I be fine if I didn't add any more underlayment? Also, should I use 2x6 or 2x8?

TIA

Rookie

PS - why does say invalid session every time until I submit at least three times?

Yes, that is the alternative to installing more subflooring/underlayment. 2 x 6's will be just fine.