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Wood Treatment

DEFINITION
CONSIDERATIONS
COMMERCIAL STATUS
IMPLEMENTATION ISSUES
GUIDELINES

  1. Precautions
  2. Borate site-applied products
  3. ACQ
  4. CCA
  5. Other Chemical Treatments
  6. Decay resistant domestic woods
  7. Borate Pressure-Treated Lumber

CSI Numbers:

063 100


DEFINITION:

Wood treatment refers to protecting wood from damage caused by insects, moisture, and decay fungi.


CONSIDERATIONS:

Three primary methods of wood treatment currently prevail: creosote pressure-treated wood, pentachlorophenol pressure-treated wood, and inorganic arsenical pressure-treated wood. 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 .

Chromated copper arsenate (CCA) is the most popular wood treatment product available today. The chemicals are inert within the material and offer protection from moisture and decay fungi. The chemicals do not penetrate into the heartwood effectively so a sealer is advisable on cut ends of CCA treated wood. Although CCA treated wood is sawn on jobsites, hardly anyone seals the cuts. All pressure treated products require adherence to safety precautions approved by the EPA. The safety precautions are listed in the Guidelines section.

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.

The toxicity of the chemicals used in wood treatment has led to research into less toxic methods such as the use of borates derived from the natural element boron (borax). Borates (from boron) are used in wood in New Zealand and Australia and offer insect protection and fire retarding benefits to wood. 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, they are effective in preserving wood; site applied borate products are available.

Borate pressure-treated wood is being offered by one company in the U.S. (primarily for the Caribbean market). They are promoting the concept of using borates for all the wood in a house. This eliminates the need for termite protection by any other means and prevents decay fungi.

Ammoniacal copper quatenary (ACQ) is a new wood preservative currently being introduced. This material employs preservative components that are listed in EPA’s classification as “General Use” pesticides. This is a less toxic material that CCA and it performs similarly.

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Satisfactory Satisfactory
Satisfactory in most conditions Satisfactory in most conditions
Satisfactory in Limited Conditions Satisfactory in Limited Conditions
Unsatisfactory or Difficult Unsatisfactory or Difficult


COMMERCIAL STATUS

TECHNOLOGY:

Borate treatment is not technologically mature in comparison with CCA treated wood. Leaching problems must be resolved for borate treatment to substitute for CCA pressure-treated wood.

SUPPLIERS:

Suppliers of site-applied borate products are uncommon. Commercial application of borate treatment is just becoming available.

COST:

Site-applied borate treatments exceed the cost of other chemical treatments due to shipping costs. Borate pressure-treated material adds about $2,500 to the costs of an average sized frame house.


IMPLEMENTATION ISSUES

FINANCING:

Available if the borate treatment is code compliant.

PUBLIC ACCEPTANCE:

There is not widespead awareness of borate treatment. However, reduced health risk should be seen as a positive characteristic.

REGULATORY:

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 Non-toxic Termite Control )


GUIDELINES

1.0 Precautions

It is required that this information be available to persons using Inorganic Arsenical Pressure-Treated Wood (CCA), Pentachlorophenol Pressure-Treated Wood, Creosote Pressure-Treated Wood.

1.1 Generic Precautions for all three types

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 which may come into contact with the 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. Treated wood 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. Whenever possible, these operations should be performed outdoors to avoid indoor accumulations or 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 use of tobacco products.

If preservatives or sawdust accumulate on clothes, launder before reuse. Wash work clothes separately from other household clothing.

1.2 Additional Precautions for Inorganic Arsenical Pressure-Treated Wood (CCA)

Wood pressure-treated with waterborne arsenical preservatives may be used inside residences as long as all sawdust and construction debris are cleaned up and disposed of after construction.

1.3 Additional Precautions for Pentachlorophenol Pressure-Treated Wood

Logs treated with pentachlorophenol should not be used for log homes.

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 crib (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 pentachlorophenol-treated wood.

1.4 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 which 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).

Coal tar pitch and coal tar pitch emulsion are effective sealers for creosote-treated wood block flooring. Urethane, epoxy, and shellac are acceptable sealers for all creosote-treated wood.

2.0 Borate site-applied products

2.1 Impel Rods

Available in various sizes in a “glass” rod.

Holes are drilled in the wood and the rods are inserted according to manufacturers calculations that considers 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%. The boric acid penetrates heartwood and sapwood stopping decay. When wood is dry the boric acid is inactive.

Example: In logs, of 8 inch diameter, one rod per linear foot is needed (rod size is 3/4″x3″)

2.2 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.

2.3 Tim-Bor

Available in a powder form.

Can be applied to wet lumber (over 20% moisture).

Can be dipped or sprayed.

2.4 Bora-Care

Available in a liquid form.

Includes a glycol solution that helps diffusion.

Can be dipped or sprayed.

3.0 ACQ

Used the same as CCA preserved material.

Currently unavailable in Texas and is more costly than CCA.

4.0 CCA

Available as Type A, B, and C. Type C is recommended as superior in resisting leaching.

CCA preserved wood does not properly fix in wood in cold weather. If buying CCA treated wood in the winter (and the wood was treated in the winter), use extra care in handling and applying since leaching of the CCA is possible, posing an environmental and health risk. When buying CCA treated wood in warm weather (above 70 degrees ), the chemicals should be fixed in the wood in 3-4 days.

Protect CCA wood with a sealer from UV degradation.

5.0 Other Chemical Treatments

ACA (ammoniacal copper arsenate); ACZA (ammoniacal copper zinc arsenate); ACC (acid copper chromate); CZC (chromated zinc chloride). These lesser known water borne preservatives are used in hard-to-penetrate woods. Safety precautions are needed.

6.0 Decay resistant domestic woods

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, Pacific yew.

7.0 Borate Pressure-Treated Lumber

One supplier currently in United States. (see Resources).

Any wood – engineered, sheathing, dimensional – can be treated by this method.

When all wood is treated in house, it will add approximately $2500 to cost.

Eliminates need for termite treatments and maintenance calls.

Penetrates heartwood (CCA does not).

Non-toxic for handling, cutting, and disposal.

Does not need to be site-treated on cut ends (CCA does).

Cannot be used in ground or water contact.