- Q.Is moisture-resistant
drywall an appropriate ceiling material for an open
porch?
A.I would not consider
moisture-resistant (MR) drywall appropriate for use
on an open porch. While MR drywall is resistant to
deterioration from moisture, it may sag from direct
exposure to moisture. MR drywall is designed to be
used behind bathroom finishes, but not to be
directly exposed to water. The joints and nails in
MR drywall are usually left unfinished, since they
will be concealed with tile or other finish
materials. The joint compound would not withstand
the weather exposure on a porch.