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Pressure Treated wood is lumber that has been placed inside a sealed
chamber and then using a combination, of an extremely high amount of
pressure and vacuum, forcing the chemicals into the lumber. Depending on
the lumber usage designation, and size, sometimes to the core. The International Residential Building Codes Guide
require all exterior wood structures to be treated for Insects,
Termites, Fungi, and, Rot, if the wood does not have a certain
measurable, natural resistance. Treating wood gives it a 20 to 25
year life span. We at Superior Services think 20 years is the absolute
minimum you should get out of your Pressure Treated Wood Fence. In fact
25 to 30 is not unreasonable.
The three types of Preservative are:
Waterborne: used for residential applications - decks and fences.
Cresote: used in commercial/industrial/marine applications - railroad ties, guardrails, pier
pilings and other marine uses.
Oil-borne: used for commercial/industrial applications - utility poles and cross arms.
Prior to 2003 “Chromated Copper Arsenic” – CCA, (an extremely toxic chemical to humans and animals), was used in all residential applications for treating exterior grade wood products. Since 2003, The United States, through the Environmental Protection Agency (EPA) has switched to using the following products for residential applications (water based):
Amine Copper Quat (ACQ): aka “Preserve”, and “Nature Wood”
Micronized Copper Quat (MCQ): aka “Micro Pro”, and “Smartsense”
Copper Azone (CA): aka “Wolmanized Natural Select”
Sodium Borate: aka “Advance Guard”
and other much less hazardous materials for treating lumber.
CCA is still authorized for use in some industrial and marine
applications. So, if your Deck was built prior to 2003, should you tear
it down, due to the fact it may have a very toxic element on and in it?
The EPA says no. Their studies show the proper application of an “oil
based” sealer can reduce or eliminate human and environmental exposure to
CCA in older Decks and also the newer chemicals in new structures.
Sealing also reduces or eliminates leaching of the chemicals into the
air or ground. The newer pressure treated chemicals react with or
precipitate (become insoluble) in the wood substrate, thus becoming
fixed inside the wood and resistant to leaching.
Pressure treated lumber comes in a variety of chemical
retention levels, expressed as “Pounds of Preservative - per cubic ft
(PCF) of wood. This is important as pertains to level of chemical in the
board, as per the application, or usage of that particular piece of
lumber. Wood rated for ground contact has to have an increased level of
protection versus framing that will be in the air. Here at Superior
Services we’ve developed charts we use when designing our decks as to
what level of treatments are required for what applications, and lumber
is purchased accordingly. We don’t just go down the The Home Depot and
pick up a load of lumber - LOL!!! The lumber you would use to frame a
deck 10’ in the air can have a lower level of protection than joists that are within 2 feet
of the ground or on the ground.
0.40 pcf for ACQRegular Chemical content not rated for ground contact such as framing, decking, and fence pickets.
0.34 pcf for MCQ
0.21 pcf for CA-B
0.15 pcf for CA-C and MCA, or
0.14 pcf for μCA-C.
0.15 pcf for ACQ,
0.15 pcf for MCQ,
0.10 for CA-B,
0.06 pcf for CA-C and MCA, and
0.05 pcf for µCA-C.
On a side note, all of your deck
fasteners, and connectors must be matched to the level of preservative in the lumber, as
the preservation material is corrosive, and will literally eat the wrong fasteners and connectors. This is very important for the
life span of the structure, and your safety. Inspect underneath your
deck every spring and fall.
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