Choosing sheathing
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Water test
The edges of the 1/2-in. oriented
strand board (OSB) that soaked in
my bathtub overnight swelled
almost 1/4 in. (and stayed
swollen), while the plywood
remained stable. The lesson?
Don’t store OSB in a full bathtub.
Kept high and dry during storage
and after installation, OSB has the
same strength and durability as
plywood but costs less.
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Fast fact
In 2001, oriented
strand board surpassed plywood
in terms of square footage produced.
OSB is now used for about
70 percent of all floor, wall and
roof sheathing in North America.
Building codes, the
Engineered Wood Association,
architects and most builders rate
plywood and oriented strand
board (OSB) equal in strength and
durability. Like-thicknesses of
these two products can span the
same distances between studs or
rafters, weigh about the same and
offer similar nail-holding abilities.
OSB has its advantages. Some
panels have a textured surface,
which makes them less slippery
when used for roof sheathing.
OSB panels often have lines at
16- and 24-in. intervals so you
know where underlying studs,
rafters and joists are for nailing. In
our area, 1/2-in. OSB costs a few dollars less
per sheet than 1/2-in. plywood.
And OSB is available in 4 x 9-ft.
sheets, which means you can
sheathe an 8-ft. tall wall and the
joists below with a single sheet.
OSB has one irritating characteristic—but only if you abuse the
stuff. The edges tend to swell when
they get wet and remain swollen
even after drying out. This results
in ridges that can “telegraph”
through shingles, and even carpet
when OSB is used for subfloors.
So store your OSB in a dry place,
then cover it with tarpaper or
siding ASAP to protect it from
the elements.
