- Q.Is it a good idea to
install vinyl siding over OSB sheathing without putting
up any housewrap or felt? I see this more and more
often, and wonder whether the OSB should be protected
since vinyl is fairly leaky. Apparently there is
nothing in the codes against this
practice.
A.Corresponding
editor Paul Fisette responds: I agree with you
that this is a bad practice. OSB is not
manufactured to withstand repeated wettings, and
over time it will deteriorate, as rainwater is
driven behind the vinyl siding. Once OSB swells, it
will not return to its original thickness, and this
permanent deformation can telegraph through to
affect the surface appearance.
As you note, most building codes unfortunately
(and incorrectly I think) don’t require
protection over OSB and plywood. Omitting the paper
not only leaves the OSB or plywood unprotected, it
also gives you no way to protect the top edge of
window and door flashings with an overlapping
layer. Water running down the sheathing can run
behind the window flanges and into the framing
cavity.