- Q.Is there anything that can
be done, short of tear-out and replacement, to prevent
the knotholes in pressure-treated pine decking from
oozing on hot days?
A.Paul R. Fisette,
director of the wood technology program at the
University of Massachusetts in Amherst,
responds: The sap in the knotholes softens and
begins to runs as it is heated by the sun. Sap is
composed of liquid and solid materials. If it is
heated to 160°F while it is being
kiln-dried, the volatile liquid substances will
flash off, leaving the solids behind in a hardened
state. Once the sap has set, it will never run
again. This doesn’t help you now, however,
since the wood in your deck was obviously not
kiln-dried at a high enough temperature during
production.
There are a couple of options. You can wait it
out; sooner or later the sap will stop running out
of the wood. In the meantime, you can clean it up
with turpentine. Or you can try to set the sap in
the knots using a heat gun. Just be careful not to
start a fire or singe the wood.