HOW OFTEN SHOULD YOU REPLACE THE ‘NATURAL OILS’ IN YOUR SHAKES?
Never. There, wasn’t that easy? Actually the idea of “replenishing
natural oils” in cedar shakes has been around a long time and until
fairly recently was a concept to which most of us blindly nodded our heads.
Listen to some of what Oregon State University Extension Service (Publication
EC1271) has to say about so-called oil replacement.
“…these oils account for less than 3% of the total mass.”
(And that was when the tree was alive!) “…applying ‘replenishing
oils to weathered shingles may be of questionable value…”
“…unless you include an effective mildicide or preservative,
an oil like linseed may provide an additional food source for mold, mildew
“Furthermore, petroleum based products are likely to be oxidized
(broken down) by sunlight, to have only a short-lived effect, and to increase
the flammability of the roof.”
So once again, how often should you “replace” something that
was barely present to begin with, that can actually encourage fungus growth,
that works for a short period it at all, and that makes your roof more
prone to fire? Never.
About half as often as you replace the natural oils. After a roof has been
pressure washed, it looks “brand new.” That’s because
it is. There is just one problem – the roof is now not as thick
as it once was. Pressure washing tears away that silvery gray layer of
wood cells, the presence and color of which could have been preserved.
Your roof has now been made thinner by anywhere from 1/8” to as
much as 3/16”. Then when your roof turns dark gray again, which
it will relatively quickly, the idea is that you “renew” your
roof by removing that much material again! I don’t get it. Why would
anyone want to remove years of useful life from their roof?
An added ‘benefit’ to pressure washing is now all that former
roof material, in addition to the debris, dirt and fungal growth (the
slimy stuff) is splattered all over your siding, windows, lawn, shrubs,
sidewalks, decks and in your gutters. We don’t use a pressure washer
to make a roof look new for the same reason we don’t use an earthmover
to make our lawn look new.