How does pressure-treated lumber work?

organisms. Find out why pressure-treated lumber holds up better -- and how it works -- in this podcast from HowStuffWorks.com.

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Episode Transcript

Speaker 1 (00:00):
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Welcome to Brainstuff from how Stuff works dot com where
smart happens. Hi, I'm Marshall Brain with today's question, how

(00:30):
does pressure traded lumber work? Wood is a great building material.
It's strong, lightweight, easily worked with tools, and relatively inexpensive.
The only problem with wood is that many varieties of bacteria, fungi,
and insects find it appetizing. When wood is in contact
with the ground or moisture for any period of time,

(00:52):
these organisms attack the wood. Untreated wood, like pine, will
only last a year or two if it's touching hot ground.
Pressure treated lumber is wood that's been immersed in a
liquid preservative and placed in a pressure chamber. The chamber
forces the chemical into the wood fibers. The pressurized approach

(01:13):
makes sure that the chemical makes it to the core
of each piece of wood. It's much more effective than
simply soaking the wood in the chemical. The most common
chemical used to treat lumber used to be chromated copper
arsenate or c C A. In two thousand three, however,
the Environmental Protection Agency restricted the use of c c

(01:35):
A in residential settings due to health and environmental concerns
about the arsenic leaching out of the wood. The most
widely used alternative to c c A is alkalin copper
quat or a CQ. Copper is toxic to most insects
and fungi that might cause de k. A c Q
binds the wood fibers very well, and it allows the

(01:57):
wood to last decades even when it's in contact with
the ground. The protection provided by the chemical depends on
the amount of chemical that the wood absorbs. In the
United States, the amount of chemical is measured in pounds
of chemical per cubic foot of wood. For ground contact,
point four pounds per cubic foot is needed. For above ground,

(02:21):
point two pounds per cubic foot is the standard. The
chemicals and treated wood are generally not very good for
humans either. I mean, if it's gonna kill bugs, it's
probably not good for us. This is why you see
warnings advising you to wear gloves, avoid breathing the sawdust
and refrain from burning treated wood. Keeping small children away

(02:43):
from treated wood is also a great idea for moral
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