The ongoing battle to preserve wood

A key to the rise and continued success of post-frame buildings has been the existence of wood preservatives that keep wood posts from rotting. Interestingly, when we trace back how wood is preserved for the future, we can unearth a lot of skeletons in the past. There have been controversy and debates centered on how best to preserve wood for future generations.

CCA’s origins
One of the most notable controversies in the last 40 years had to do with chromated copper arsenate. CCA was invented in 1933, but did not become widely used until the late 1960s and early 1970s. Forty years ago when Rural Builder launched, the main preservatives were CCA, creosote, and pentachlorophenol, also called penta. In 1966, CCA was the fourth-most-used treatment for preserving wood from rot, according to Huck DeVenzio, manager, marketing communications, Arch Wood Protection. Subsequently, CCA flourished and became the dominant preservative.
When CCA first came on the scene, it was formulated with chemicals in salt form and later, manufacturers switched over to an oxide formulation, which was thought to be less harsh on metal. It was also less likely that animals would lick it because they would not be enticed by its salt content. E-Wood.jpg

Controversy ends CCA’s reign
In its heyday, CCA, a water-based preservative, stole a lot of business from creosote and penta because it penetrated wood better, providing a cleaner surface than wood treated with oil formulations. “The surface was cleaner for builders, animals, and end users who might lean against it or brush against it. If CCA hadn’t been invented, I don’t think that people would build decks with creosote or penta because you couldn’t sit on them,” says DeVenzio.
CCA’s reign came to an end in 2003 when wood treated with CCA was voluntarily removed from residential applications because it contained arsenic.
The industry responded by offering a menu of other chemicals that don’t contain arsenic, including:
– Alkaline Copper Quat (ACQ), which uses the trade names Preserve and NatureWood;
– Copper Azole (CA), which goes under the trade names Natural Select and Wolmanized Natural Select;
– Sodium Borate (SBX-DOT), which goes under the trade names Advance Guard, Sill Bor, Pac-Bor, and TimberSaverPT; and
– Ammoniacal Copper Zinc Arsenate (ACZA), with the trade name Chemonite.
“The CCA controversy was more a matter of emotion over science,” says DeVenzio. “Concern spread without looking at its history or medical science until the point where we were fighting so many battles that it wasn’t worth it to fight in the residential area.”
Aside from the arsenic fear, CCA was the marvel preservative with few, if any, shortcomings. In fact, in commercial and agricultural building, CCA is still used. “There is no concern about CCA’s effect on contractors or professionals who build as a matter of course and no concerns with users of the buildings either. It was a matter of well-meaning people knowing that forms of arsenic are poisonous and this preservative had a form of arsenic in it. On that fact alone, it was hard to convince a grandmother to let kids play on a CCA-treated wood swing set. She didn’t want to take any chances.”
One change that the demise of CCA brought about is forcing builders to learn what hardware to choose. “The newer products look, last, and perform very much like traditional CCA-treated wood,” says DeVenzio. However, “the new treatments are slightly more corrosive, and greater awareness of hardware is necessary. If builders and remodelers follow the recommendations of the wood preservation industry, which are close to the new guidelines of the model building codes, they can expect no corrosion problems.” E-Wood2.jpg

Creosote and penta: Pros and cons
The wood preservatives that were around 40 years ago continue to exist in use today. “They are all effective. They all work and they all work well. Properly treated wood lasts, people don’t question that any more. The positives and negatives of each don’t have to do with longevity, but with each product’s side issues,” says DeVenzio.
Where aesthetics are not important, such as in the case of post-frame building where wood products are covered by a wall or won’t show, preservatives such as creosote, which yields a black finish, or penta, which results in a green or brown surface due to its copper content, are popular choices. “For many post-frame applications, the most important thing is cost, since beauty may be relatively unimportant and they’ll all last,” DeVenzio explains.
On the downside, creosote, which is made with coal and tar, is in short supply these days, while penta, an oil-based preservative, is relatively expensive. “That makes copper a good alternative, although it isn’t cheap either,” says DeVenzio. With all things being equal, “cost helps guide which way buyers go and which kind of treated wood buyers will want more.”
In 1976, there was some controversy over penta because it contains dioxin, a toxic chemical. “I heard a guy say it was the most studied preservative because it has dioxin in it and that does scare people,” DeVenzio says. “I don’t know that there have been any problems with it because the Environmental Protection Agency hasn’t banned or discontinued its use.”
Other than cost and aesthetics, “there aren’t any real chemical or scientific issues that make one preservative the preferred choice over another,” DeVenzio explains. “It is really personal preference.”

Improvements to the process
While there have been some improvements and refinements to the actual wood preservatives over the years, they have been subtle. Far more important are the changes that have taken place to improve how wood is processed and the industry’s overall quality control. DeVenzio recalls that 40 years go, treatment plants had big doors that were bolted shut during the pressure treatment process. The chambers were equipped with oversized controls and dials that looked like they came right out of a science fiction movie. Today, the controls are automated to precisely dispense just the amount of preservative needed. Everything is computerized. Manufacturers plug in the size of the wood and species, and the computer calculates how much pressure is needed to treat the wood thoroughly.
Another advancement is adding third-party inspection to the treatment process, which ensures that what the manufacturer is saying is accurate. “Now the end user can be sure that he is getting something that is processed correctly, follows the rules, and meets industry standards,” says DeVenzio.

What’s next?
What will the next 40 years hold? DeVenzio predicts the next generation of preservatives will not contain any metallic elements, unlike CCA, which contains three metals: arsenic, copper, and chromium. “A lot of people would like an all-organic preservative,” he says. “We have it now, but it is not effective for in-ground applications. If we can come up with a non-metal preservative that can be used for in-ground contact and is effective, that’s the next thing for treated wood.”

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