PRESERVATIVE TREATED LUMBER - CONTENTS: Deck framing lumber treatment methods. How to use pressure treated lumber. Health Concerns for Chromated-Copper Arsenate (CCA) Pressure Treated Lumber. Advice for Existing Structures Built Using Chromated-copper Arsenate (CCA) Treated Lumber. Health Precautions for Alkaline Copper Quat (ACQ)-Treated Lumber. Treatment Levels & Durability of Alkaline Copper Quat (ACQ)-Treated Lumber. Borate Treatment for Lumber & Deck Framing. Increased Corrosion Potential for ACQ and Copper Azole-Treated Lumber
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Preservative treated wood: health & environmental concerns when working with or using treated lumber: this article discusses deck framing lumber treatment methods, the use of pressure treated lumber, Health Concerns for Chromated-Copper Arsenate (CCA) Pressure Treated Lumber.
Advice for Existing Structures Built Using Chromated-copper Arsenate (CCA) Treated Lumber, Health Precautions for Alkaline
Copper Quat (ACQ)-Treated Lumber, and Retention Ratings: Treatment Levels & Durability of Alkaline
Copper Quat (ACQ)-Treated Lumber.
This article series discuss best porch & deck construction practices, including choice of framing materials, decking or flooring choices & installation, how to select and use deck and porch structural and flooring fasteners, actual deck & porch framing construction details & connections, deck joist & beam span tables, how to build leak-proof rooftop decks, construction of covered & screened porches, deck & porch railing construction & materials, choices of finishes and stains for decks & porches, and past & current deck lumber preservative treatments with related health & environmental concerns.
Most builders choose pressure-treated lumber for the
structural framework because of its low cost and high
durability. At this time there are few viable alternatives.
However, composite and synthetic products are beginning
to enter the market and are worth considering, especially
for environmentally sensitive sites, such as wetlands or
other applications where clients object to the use of treated
lumber (see Table 4-1 shown just below).
[Click any image or table for a larger, more-detailed version.]
Pressure-Treated (PT) Lumber
The vast majority of residential decks were framed with
lumber treated with chromated-copper arsenate (CCA)
until 2004, when CCA was phased out and replaced primarily
by alkaline copper quat (ACQ) and copper azole. The
treated lumber is typically Southern yellow pine in the eastern
United States and hem-fir in the West. The more expensive
and stronger Douglas fir is also used in the West,
but it is more likely treated with the waterborne treatment
ammoniacal copper zinc arsenate (ACZA).
Incising Lumber for Treatment Penetration
Both Douglas fir and hem-fir are typically “incised”
with surface cuts for better penetration of the treatment
chemical. Even with incising, however, full chemical
penetration is rarely achieved with these species, so the
center of that wood remains vulnerable to rot, particularly
in 4x and larger material.
With these species, effective field
treatment of holes and cuts with a liquid preservative is
Health Concerns for Chromated-Copper Arsenate (CCA) Pressure Treated Lumber
Despite CCA’s track record as an
effective, economical wood preservative, its safety has long
been questioned by health and environmental advocates.
Their primary focus has been CCA’s heavy concentration of
arsenic, a known carcinogen.
Although most experts agree that leaching of arsenic from CCA lumber is minimal and
poses negligible health risks to end users, the industry
acknowledges that CCA does pose risks to workers who
handle the wet wood or burn scraps, and significant pollution
around treating plants has been well documented.
Phase Out of Chromated-copper Arsenate (CCA) Treated Lumber
In response to these concerns, manufacturers
began a voluntary phase out in 2003 of all CCA treated
lumber for noncommercial applications. Starting
January 1, 2004, the Environmental Protection Agency
(EPA) banned the manufacture of CCA-treated lumber
intended to be used in residential settings, including retaining
walls, decks, fencing, and playground equipment.
Pressure-treated shakes and shingles were exempted. CCA
treatment will also still be available for plywood and heavy
timbers used in commercial, industrial, and marine applications.
Existing stocks of CCA-treated lumber were
mostly depleted by the end of 2004.
Advice for Existing Structures Built Using Chromated-copper Arsenate (CCA) Treated Lumber
The EPA has issued no warnings
regarding existing installations of CCA-treated lumber.
However, for homeowners who are concerned about potential
exposure to chemicals leaching out of the wood,
researchers at the USDA Forest Products Laboratory (FPL)
recommend periodically treating the pressure-treated
lumber with a water-repellant or a semitransparent penetrating
stain. Film-forming finishes, such as paints, are not
New Wood Preservative & Deck Lumber Treatment Chemicals: Alkaline
Copper Quat (ACQ) and Copper Azole
The two main chemicals
replacing CCA are the waterborne compounds alkaline
copper quat (ACQ) and copper azole.
Copper azole Type B
(CA-B) has largely replaced Type A (CBC-A) in the
United States and Canada.
Both ACQ and copper azole
perform as well as CCA and are free of any EPA-listed
As with CCA-treated wood, premium
treated lumber is available with a factory-applied
With significantly higher copper content
than CCA lumber, the new materials are 10 to 15% more
Of greater concern is the fact that the higher
concentration of copper makes the lumber more corrosive
to certain metals and metal coatings (see “Increased
Corrosion Potential,” next page).
Health Precautions for Alkaline
Copper Quat (ACQ)-Treated Lumber
Despite the lack of chromium,
arsenic, or other hazardous chemicals, wood treated with
copper quat (ACQ) and copper azole carry essentially the same handling
instructions as CCA-treated materials. Workers handling
ACQ and copper azole are still advised by the EPA to wear
gloves or wash hands after contact, wear a dust mask when
cutting, and not to burn the scraps. Like CCA-treated
wood, it is not recommended for direct contact with food
or drinking water.
While most CCA lumber was rated
for ground contact, manufacturers are holding down costs
with ACQ and copper azole by limiting treatment levels to
the expected application of the lumber. For example, deck
boards, 2x6s, and 4x4s at the lumberyard will typically have
three different treatment levels (Table 4-2 below).
In most cases,
lumber will be stamped or tagged with a designation such
as “decking,” “above ground,” “ground contact,” or “PWF”
(permanent wood foundation). Make sure the material
purchased is rated for the intended application or one level
Borate Treatment for Lumber & Deck Framing
Wood preservatives based on borate
compounds have been used for decades abroad and are slowly
becoming available in the United States. Borates are noncorrosive
to metals and harmless to pets and humans, but
they are very effective against insects and decay. Borate’s
main limitation is its tendency to leach out of wood that
is buried in soil or exposed to regular wetting, making it
unsuitable for decks or other exterior applications.
techniques to better fix the compounds into wood are under
development, however, and may soon offer a viable alternative
to copper-based treatments.
Increased Corrosion Potential for ACQ and Copper Azole-Treated Lumber
Because of their
higher concentrations of copper, ACQ and copper azole are
significantly more corrosive to aluminum, steel, and galvanized
coatings than CCA (see “Galvanic Corrosion,” page 83).
Preliminary tests have also shown that formulations with
ammonia-based carriers (used for better penetration in heartwood
species such as Douglas fir) are more corrosive than
those with an amine or hybrid bases.
Many factors affect corrosion
rates, but some studies have found ACQ-treated wood to corrode untreated steel up to four times faster than CCA
and to attack galvanized coatings at twice the rate of
Biodegradable Wood Preservatives
A recent addition to wood treatments is Wolmanized® L3 is described as a low-impact, long-lasting preservative treatment with lasting resistance to termites and fungal decay. - Thanks to deck expert Mark Morsching, Everlast for this update, October 2010. (see Deck & Porch Products, Manufacturers) below.
Deck & Porch Resources, Products, Manufacturers: Where to Buy
Arch Wood Protection, Arch Wood Protection, Inc., Arch Treatment Technologies, Inc., 5660 New Northside Dr., Suite 1100
Atlanta, GA 30328, (678) 627-2000- http://www.archchemicals.com
Arch produces Wolmanized® pressure-treated wood
Copper-azole and borate-treated wood products with
optional water repellent) and
Wolmanized® L3, described as a low-impact, long-lasting preservative treatment with lasting resistance to termites and fungal decay. The biocides used in Wolmanized® L3 are biodegradable so they do not accumulate in soils below a deck constructed of this material. 2007 MSDS for Wolmanized Treated Wood, web search 11/9/2010, original source:
http://petersonwoodtreating.com/PDF/Wolmanized%20L3%20Outdoor%20Wood%20MSDS%20041007.pdf 1998 MSDS for Wolmanized Treated Wood, web search 11/9/2010, original source: http://longlifetreatedwood.com/pages/msds%20form.htm
Also see Wood Construction Products MSDS
Chemical Specialties www.treatedwood.com
ACQ-treated wood products with optional water repellent
Chemical Specialties, Inc. . Great Southern Wood Preserving, Incorporated, P.O. Box 610, Abbeville, Alabama 36310,
Tel: 334) 585-2291
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Mark Morsching, Everflashing, Tel: 800-550-1667, Email: firstname.lastname@example.org. The Everflashing product comes in G-185 and Stainless Steel and is intended for use with treated lumber with copper in it. Everflashing produces a variety of specialty flashing products including flashings for use with decks at deck ledgers and deck perimeters.
Summerblue Arts Camp., Two Harbors MN, Lon Church, Director, c/o: Two Harbors High School
405 4Th Avenue, Two Harbors, Minnesota 55616, United States Email: email@example.com
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