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|Sustainable Building Sourcebook
|Chapter: Health and Safety
06300 Wood Treatment
Wood treatment refers to protecting wood from damage caused by insects, moisture and decay, and fungi. In wood-framed walls, treated wood is used as the base plate in contact with a concrete slab. Treated wood is also used in outdoor applications where the wood will be exposed to harsh conditions. These applications include decks, walkways, and direct ground contact. At present, there is not an environmentally sound method for disposal of treated wood. Every effort should be made to minimize the use of treated wood by using alternate materials or designing alternative details. Treated lumber is not allowed under the Final Rule of the National Organic Program (NOP).
On December 31, 2003, the pressure treated wood industry discontinued the use of chromated copper arsenate (CCA) as a wood treatment for most applications. It is still used for marine pilings and utility poles. There are several arsenic-free treatments on the market, including borates, alkaline copper quaternary (ACQ), and copper-boran-azole (CBA). Each of these options has inherent hazards and none should be used where they will come into contact with water. Copper and borate will leach, and both are toxic to plants, pets, and marine life. As long as all the safety precautions are followed, borate treated wood is generally considered to be a safe choice.
A number of alternatives to treated wood are readily available, such as steel, composites and engineered wood products, cement board panels, concrete blocks, and concrete. The National Sustainable Agriculture Information Services has an excellent factsheet on Organic Alternatives to Treated Lumber.
|All major wood suppliers carry borate-treated wood products.
| The controversy surrounding CCA treated wood and the EPA's involvement in its phase-out has raised public awareness concerning the safety of different types of wood treatment options.
| Any wood within 6 inches of the finish grade must be factory treated or have natural resistance (e. g. heartwood of cedar, redwood, or black locust). (See also Integrated Pest Management section in this Sourcebook .)
There are three primary methods of pressure treating wood: creosote, pentachlorophenol, and inorganic arsenical. The pressure-treating process is done by commercial facilities and made available to users in the final wood product. Copper napthenate, zinc napthenate, and tributyltin oxide are other wood treatment options that can be site applied. All of these treatment processes involve dangerous chemicals and all require adherence to safety precautions approved by EPA (see Guidelines).
EPA regulations govern the manufacture of pressure-treated materials and require extensive environmental safety precautions. Wood treatment does offer a method to extend the usable life of our wood resources, but treated wood should be handled carefully to protect against inhaling or ingesting its dust. It should not be burned, and should be considered toxic waste when disposing sawdust and scraps.
Several different types of treated wood are available.
ACQ is a wood treatment containing alkaline copper and quaternary ammonium compounds. It does not contain arsenic or chromium. "Preserve" is a brand name for wood products treated with ACQ. Copper is the principal active ingredient, providing protection against termites and fungal decay.
CBA-A and CA-B are two different treatments that are formulated from copper, boron, and azole. As with ACQ, copper is the principal active ingredient, protecting against termites and fungal decay. Protection against copper-tolerant fungi is provided by an organic azole also used in fungicides applied to fruits, peanuts, and other crops. A third ingredient is boron acid, which is found in eyewash, vitamins, and antiseptics. In damp conditions, boron acid diffuses through wood and offers supplemental protection. This preservative is not a restricted use pesticide and does not meet the definition of hazardous waste. "Wolmanized Natural Select" is a brand name for wood products treated in this technique.
Testing has indicated that the above two treatment methods are more corrosive to metal fasteners and connectors than CCA treated wood previously was. Use of ACQ, CBA-A or CA-B might require the use of stainless steel connectors and fasteners or at least those with thicker galvanized coatings to withstand this higher corrosivity. Contact the treated wood chemical supplier for more specific information on this developing area of research.
Borate pressure-treated wood uses an EPA registered borate wood preservative for protection against termites, carpenter ants, and fungal decay. This type of wood can be used in aboveground, weather-protected structural framing in residential and commercial applications. However, full-scale commercial introduction of borates in the U.S. awaits resolution of the leaching problem of borates. Since borates are water soluble, water dilutes them and leaves the wood unprotected from decay after a period of time. In a location unexposed to water, borates are effective in preserving wood, and site-applied borate products are available.
1. Use building methods that reduce moisture access to and/or build-up on wood products.
One method is to build a high enough foundation (at least 8-12 inches, frame grade) to reduce the chances of water-retaining soil building up against it. This is something that needs to be checked by the homeowner from time to time. Another method is to use a sturdy sheet of polyethylene plastic under the concrete slab to reduce moisture wicking up from the ground and through the concrete.
For pier foundations, be sure to remove water-absorbing forms that can retain water or attract termites. In addition, it is good practice to place a non-absorptive material between the concrete pier and wooden beams such as a plastic or metal anchor or plate. Proper building design and installation of building materials have the largest effect on opportunities for moisture to affect wooden building materials. Comprehensive understanding and maintenance of the thermal envelope of the home, including the HVAC and ventilation systems, also has a great effect on the control of the inevitable movement of moisture within the building.
2. Use building methods that hinder the attraction of termites to wood within the home.
The use of termite shields and barriers as well as other integrated pest management (IPM) practices described in the "Integrated Pest Management" section of this Sourcebook will be of great service in reducing the chances of a termite attack.
3. Use alternative materials to wood where possible and appropriate.
For wood frame buildings, building material alternatives such as lumber made of recycled plastic or wood/plastic composites are good options for moisture-prone areas such as sill plates, doorframes and thresholds, porches and outdoor decks, and stairs.
Fiber/cement or fiber/plastic materials for siding, roofing, soffits, and fascias are also good low-maintenance alternatives to wood because they do not rot or attract termites. Alternatives to wood framing such as steel, concrete, structural insulated panels, earth, and straw are also methods that eliminate most of the termite and some of the moisture problems associated with wood frame construction. Refer to other sections of this Sourcebook for information on these systems.
4. Use naturally pest resistant woods, such as Black Locust for fenceposts, or high resinous cedar.
The U.S. Environmental Protection Agency requires that this information be available to persons using Pentachlorophenol Pressure-Treated Wood and Creosote Pressure-Treated Wood.
Generic precautions for all types of treated wood
- Do not use treated wood under circumstances where the preservative may come in contact with food or animal feed, like food containers.
- Do not use treated wood for cutting-boards or countertops.
- Only treated wood that is visibly clean and free of surface residue should be used for patios, decks and walkways.
- Do not use treated wood for construction of those portions of beehives that may come into contact with honey.
- Treated wood should not be used where it may come into direct or indirect contact with public drinking water, except for uses involving incidental contact such as docks and bridges.
- Dispose of treated wood by ordinary trash collection or burial. It should not be burned in open fires or in stoves, fireplaces, or residential boilers because toxic chemicals may be produced as part of the smoke or ashes. Treated wood from commercial or industrial use (e.g., construction sites) may be burned only in commercial or industrial incinerators or boilers in accordance with state and federal regulations.
- Avoid frequent or prolonged inhalation of sawdust from treated wood. When sawing and machining treated wood, wear a dust mask, goggles, and protective clothing. Whenever possible, these operations should be performed outdoors to avoid indoor accumulations of airborne sawdust from treated wood.
- When power sawing and machining, wear goggles to protect eyes from flying particles.
- Wash exposed areas thoroughly after working with the wood and before eating, drinking and touching the eyes, nose or mouth.
- If preservatives or sawdust accumulate on clothes, launder before reuse. Wash work clothes separately from other household clothing.
Additional Precautions for Pentachlorophenol Pressure-Treated Wood
- Logs treated with pentachlorophenol should not be used for log homes or exposed in any way in a home's interior.
- Wood treated with pentachlorophenol should not be used where it will be in frequent or prolonged contact with bare skin (for example, chairs and other outdoor furniture), unless an effective sealer has been applied.
- Pentachlorophenol-treated wood should not be used in residential, industrial, or commercial interiors except for laminated beams or for building components which are in ground contact and are subject to decay or insect infestation, and where two coats of an appropriate sealer are applied. Sealers may be applied at the installation site.
- Wood treated with pentachlorophenol may be used in the interiors of farm buildings which are in ground contact and are subject to decay or insect infestation and where two coats of an appropriate sealer are applied, except where there may be direct contact with domestic animals or livestock which may bite or lick the wood. Sealers may be applied at the installation site.
- Do not use pentachlorophenol-treated wood for farrowing or brooding facilities.
- Do not use pentachlorophenol-treated wood where it may come into direct or indirect contact with drinking water for domestic animals or livestock, except for uses involving incidental contact such as docks and bridges.
- Urethane, shellac, latex, epoxy, enamel, and varnish are acceptable sealers for penta-chlorophenol-treated wood.
Additional Precautions for Creosote Pressure-Treated Wood
- Wood treated with creosote should not be used where it will be in frequent or prolonged contact with bare skin (for example, chairs and other outdoor furniture), unless an effective sealer has been applied.
- Creosote-treated wood should not be used in residential interiors. Creosote-treated wood may be used in interiors of industrial building components that are in ground contact and are subject to decay or insect infestation. For such uses, two coats of an appropriate sealer must be applied. Sealers may be applied at the installation site.
- Creosote-treated wood may be used in interiors of farm buildings for building components which are in ground contact and are subject to decay or insect infestation, and if two coats of an effective sealer are applied, except where there may be direct contact with domestic animals or livestock which may crib (bite) or lick the wood. Sealers may be applied at the installation site.
- Do not use creosote-treated wood for farrowing or brooding facilities.
- Do not use creosote-treated wood where it may come into direct or indirect contact with drinking water for domestic animals or livestock, except for uses involving incidental contact such as docks and bridges.
- Avoid frequent or prolonged skin contact with creosote-treated wood. When handling the treated wood, wear long-sleeved shirts and long pants and use gloves impervious to the chemicals (for example, gloves that are vinyl-coated).
Borate Site-Applied Products
- Available in various sizes in a "glass" rod.
- Holes are drilled in the wood and the rods are inserted according to manufacturers' calculations that consider the size of the wood and the amount of boric acid needed to protect the wood.
- The rods contain boric acid that is absorbed by the wood when the moisture content of the wood exceeds 25 percent. The boric acid penetrates heartwood and sapwood, stopping decay.
- When the wood is dry the boric acid is inactive.
- In logs of 8-inch diameter, one rod per linear foot is needed (rod size is 3/4" x 3").
Auro Borax Wood Impregnation No. 111
- Effective against fungus; preventive against insects; suitable for brush application, spray application, or dipping.
- Must be diluted according to method of application, type of wood, and wood moisture content.
- Is corrosive in solution.
- Available in a powder form.
- Can be applied to wet lumber (over 20 percent moisture).
- Can be dipped or sprayed.
- Available in a liquid form.
- Includes a glycol solution that helps diffusion.
- Can be dipped or sprayed.
Along with cedar and redwood, the following woods are considered resistant or very resistant to decay: bald cypress (old growth), catalpa, black cherry, chestnut, Arizona cypress, junipers, black locust, mesquite, red mulberry, burr oak, chestnut oak, gambrel oak, Oregon white oak, post oak, white oak, osage orange, sassafras, black walnut, and Pacific yew.
- Any wood--engineered, sheathing, dimensional--can be treated by this method.
- Eliminates need for termite treatments and maintenance calls.
- Penetrates heartwood
- Non-toxic for handling, cutting and disposal.
- Does not need to be site-treated on cut ends
- Cannot be used in contact with ground or water.
Texas Forest Service
Texas A&M University
100 Research Parkway
College Station, TX 77843-2136
Pressure treated materials are commonly available at all building material outlets
Austin Wholesale Decking Supply
10900 N Lamar Blvd.
Austin, TX 78753
Austin Lumber Company
North Texas Flameproof
2415 E. 5th St
Austin, TX 78702
2653 Warfield Ave.
Fort Worth, TX 76106
Arch Wood Protection, Inc.
1955 Lake Park Dr., Ste. 250
Smyrna, GA 30080
"WolmanizedÆ Natural Select TM" copper azole treated lumber
Aztec Pest Service
Austin, TX 78704
110 W. Elizabeth
Austin, TX 78704
Environment Sensitive Pest Control
726 Oakwood Loop
San Marcos, TX 78666
215 Dunavant Dr.
Rockford, TN 73853
Wood Preserving Division
1016 Everee Inn Rd.
Griffin, GA 30224
Fax: (770) 233-4200
8908 Georgian Dr.
Austin, TX 78753
200 East Woodlawn Rd., Ste. 250
Charlotte, NC 28217
Search for local retailers online
American Forest and Paper Association
Washington, DC 20036
American Wood Protection Association
Bio Integral Resource Center
Berkeley, CA 94707
Non-profit education organization produces publications, newsletters, and handbooks
Southern Forest Products Association (Southern Pine Council)
Treated and Residential Markets Manager
Kenner, LA 70064
TCEQ Creosote Factsheet (http://www.tceq.state.tx.us/files/gi-285.pdf_4447068.pdf)
Organic Alternatives to Treated Lumber (http://attra.ncat.org/attra-pub/lumber.html)
US EPA CCA Factsheet (http://www.epa.gov/oppad001/reregistration/cca/)