In a message dated 1/25/01 7:31:29 AM Mountain Standard Time,
[EMAIL PROTECTED] writes:
<< Actually, they orient the strands in OSB in alternating layers. Just as
with
plywood, they run the chips so the grain runs lengthwise in one layer,
crosswise in another layer, so you get a balanced material that's has much
the same properties as plywood, and is stronger than solid lumber.
>>
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.
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