Why
does Lumber Crack and Twist?
“Lumber
Expands and Contracts as it absorbs moisture from the air, and as it
dries it does predictable things”
Look at the end grain.
No tree is perfectly straight, so
you won’t find a
perfectly straight piece of lumber. Due to the shrinkage during the
drying
process you won’t find a perfectly square piece of lumber either.
Extreme
cracks and twisting is by far the easiest flaw to spot in an outdoor
project.
It is simple, If you can see the
core of the
tree, expect it to twist and crack badly.
Proof: you need only to look at
the end grains of the most twisted posts in a lumberyard to see this
type of
pattern on an end grain. Even a piece of firewood will show you the
cracking
pattern.
When Ordering Lumber…..
·
Order all the framing lumber from
the same lift. i.e. All 16’. Whatever
length will result in the least amount of waste. Different lifts often
come
from different mills and often over a matter of days the size of a
joist will
vary up to ¼ “. This will cause a deck which appears to be uneven.
·
Order all the decking lumber from
the same lift. I’ve seen variances of
up to 3/16” in decking thickness.
There
is now a product called 5/4 decking. It has
radiused edges (curved), and is a good ¼” thinner than standard
decking. It’s
been sanded and finished more completely but it is thinner and will not
last
quite as long. When framing for this decking take account that you may
need
shorter centers to get the same stability from the deck.