It is protected with a copper-based preservative copper azole containing an organic fungicide. The conditions that are favorable to fungal and insect infestation also foster metal corrosion.
Consequently, metal products in contact with pressure-treated wood must be corrosion-resistant. Note that many building codes regard preserved wood as one product, regardless of the formulation used for treatment. However, there are differences between copper-based and borate-based preservatives used for indoor applications. Hot-dipped galvanized or stainless steel fasteners and connectors are recommended for use when lumber is treated with a copper-based preservative, including CCA.
Two brands sold locally are Trex and ChoiceDek. Other options are to use metal, concrete, or a wood that naturally repels insects such as cedar, juniper, or ironwood. Arsenic-treated lumber would be a hazardous waste except that a special state exemption allows it to be disposed of in lined landfills.
Do not bring arsenic-treated wood to the compost site! Do not chip it for use as mulch. Open Daily 8 a. Gates close at p. Wash hands thoroughly with soap and water not a waterless hand cleaner after playing on or handling arsenic-treated wood. Keep children and pets from underneath decks. Do not store toys or tools under decks made of arsenic-treated wood. Avoid growing vegetables in beds lined with arsenic-treated wood. If you do raise vegetables in an old treated-wood raised bed, keep your rows at least 15 inches away from the timbers.
You could plant flowers next to the wood, instead. You could also install a plastic liner between the boards and the soil. Place a tablecloth on picnic tables made of arsenic-treated wood to prevent food from taking up arsenic.
Avoid pressure-washing arsenic-treated wood , and avoid using an acid deck wash or brightener that contains chlorine. These treatments speed up the leaching of arsenic out of the wood. Wear gloves, goggles, and a dust mask when sanding, sawing, or drilling arsenic-treated wood. Many of these applications are still used in practice today.
Pressure-treating with preservatives Wood exposed to the elements eventually falls prey to insects or fungal organisms that cause decay through a natural process. For this reason, it is important to protect wood and make it less desirable to decay organisms. This is done through the process of pressure-treating wood with preservatives.
To facilitate the production of pressure-treated wood products, the preservatives are manufactured using either oil or water as solvents to assist with penetration into the wood. Oilborne preservatives Oilborne preservatives include creosote—a byproduct of the coking process in steel production first introduced in the early s. Another oilborne preservative, pentachlorophenol PCP , was introduced in Canada in the s and is primarily used for utility poles and cross-arms but can be specified to treat timber for construction.
The oily nature of these preservatives helps stabilize the wood and protects it from moisture and wood-destroying organisms. It was introduced to the residential construction market in the s to provide an alternative to more costly naturally durable wood species. As a competitively priced alternative with similar service life, CCA pressure-treated wood products in Canada allow for the use of more plentiful Canadian species such as spruce, pine, and fir.
Thedo-it-yourself market requires products that are simple to work with and easy to install. It was CCA that initially assisted in the popularity of pressure-treated wood in outdoor residential applications and grew the market for future generations of treated wood products. Since the s, wood has been pressure treated with chromated arsenicals to protect wood from rotting due to insect and microbial agent attack and wood-boring marine invertebrates. From the s to the early s, the majority of the wood used in outdoor residential settings was chromated arsenical-treated wood.
EPA has classified chromated arsenicals as restricted use products, for use only by certified pesticide applicators. It can be used to produce commercial wood poles, posts, shakes, shingles, permanent foundation support beams, pilings, and other wood products permitted by approved labeling. Read more about CCA. Creosote has been used since as a heavy duty wood preservative.
Creosote is obtained from high temperature distillation of coal tar. Pesticide products containing creosote as the active ingredient are used to protect wood against termites, fungi, mites and other pests that can degrade or threaten the integrity of wood products. Currently, creosote is used for commercial purposes only; it has no registered residential uses. Creosote is a restricted use pesticide that can be used in outdoor settings such as in railroad ties and utility poles. Indoor applications of creosote are prohibited as well as application to wood intended for use in interiors or for use in contact with food, feed, or drinking water.
Read more about creosote. Pentachlorophenol PCP was registered as a pesticide on December 1, PCP was one of the most widely used biocides in the United States before when pentachlorophenol uses as an herbicide, defoliant, mossicide and disinfectant were removed from product labels.
Currently, there are no registered residential uses. PCP is a restricted use pesticide that is used for commercial purposes, mainly for treating utility poles. Only pressure and thermal treatments of PCP are allowed. Read more about PCP. Propiconazole is a triazole fungicide that was first registered in Propiconazole has been approved by EPA for preserving wood used in millwork, shingles and shakes, siding, plywood, structural lumber and timbers and composites that are used in above ground applications only.
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