What is Pressure Treated Lumber?

Stacks of lumber

What is pressure treated lumber and what is it used for? Pressure treated lumber in
my region of the country, New England, is Southern Yellow Pine species, which is then
injected with a preservative to protect the lumber from outside elements such as fungi and
insect damage. The treated lumber can have a life span of approximately forty years,
which can drastically vary depending on how it’s used and where it is used.
Generally, decks, exterior staircases, Pergolas, and any area of a structure that touches the
ground has a combination of treated lumber built into it.

The process of injecting preservative chemicals into the lumber involves a kiln and
vacuum pump, and there are several methods that are achieved by mill yards. The obvious
difference between kiln dried lumber and pressure treated lumber is the moisture content and the
appearance of the lumber, which is a greenish hue. Pressure treated lumber can typically have a
moisture content between 45-90%, which is noticeable when compared to kiln dried
lumber that ranges between 6-8%. Particularly treated lumber is the best options for decks.

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The chemicals used in pressure treated lumber have evolved through the years.
Depending on the region of the country that you live in, lumber chemicals change from an
arsenic based formal to a more environmentally sound product in 2003. The arsenic based
formal had been used since the 1930’s and like most products in the construction industry,
it was a slow transition to a more human and environmentally friendly product.