[VAC] Re: OSB Floor, another benefit

[Agrijeep@xxxxxxx]

Another touted benefit of OSB over plywood is that being a manmade 
composition material, the OSB expands at the same rate in both (all?) 
directions, front to back and side to side, as local humidity changes.  
Plywood, by contrast, like any other organic ("original") wood, expands 
something like 3 to 4 times as much with the grain than across the grain 
(that's the concept, I'm not a woodworker so do not know the precise ratios, 
but you get the idea).  Even though layered alternatively, plywood fights 
itself internally to expand and contract at different rates for each layer. 
Plywood also has a greater chance of having internal voids in the various 
layers where moisture can collect.  OSB is structurally more stable than 
plywood, which is why it is used behind veneer in fine grade furniture and in 
many other applications.  

  The appearance of OSB reminds me of those El-Cheapo chip board storage 
cubes that held my prized round vynal discs in college (anyone remember those 
things, records?).  Those old cubes would either melt or expand grotesquely 
upon contact with water, hence my dislike of them and initial apprehension of 
OSB.  

Fred C.
Denver, CO.