Buzz
Experienced woodworkers understand that wood varies in type and suitability for different projects. Beyond the distinctions based on the tree species (such as maple, oak, or birch), the treatment process, particularly pressure treatment, plays a crucial role in determining its application.
When purchasing new lumber, the label typically indicates whether it’s pressure-treated (if unsure, consult a store employee). However, if you acquire wood through other means and lack experience, identifying its treatment status can be challenging.
Luckily, there are several methods to determine if wood has been pressure-treated. Wade Shaddy, a hardwood furniture expert, outlines these techniques in an article for Hunker. Here’s a breakdown of how to identify it and why it’s important.
What does pressure-treated wood mean?
The Oklahoma State University Extension explains that pressure-treating wood involves injecting preservative chemicals deep into the wood’s cellular structure. These chemicals protect the wood from decay caused by moisture, insects (such as termites), and fungi, thereby extending its lifespan.
What chemicals are used in this process? Before 2003, chromated copper arsenic (CCA) was the primary preservative. However, due to the harmful effects of arsenic on humans and the environment, the lumber industry and the Environmental Protection Agency (EPA) agreed to phase out CCA-treated wood in most residential construction projects.
How can you identify pressure-treated wood?
According to Shaddy, determining if wood is pressure-treated is usually simple. Older pressure-treated wood often has an olive-green hue, while newer pieces are marked with a stamp. In some cases, they may also include an alphanumeric code indicating the level of toxicity.
When the stamp includes terms like “Borate,” “Tim-Bor,” or “Hi-Bor,” it indicates the wood has been treated with borate. This treatment offers protection similar to CCAs but is considered safe for both indoor and outdoor use, as Shaddy explains. Occasionally, manufacturers use a greenish patina instead of a stamp to signify borate treatment. Shaddy notes that this color is brighter than the traditional green tint used on CCA-treated lumber.
Lastly, Shaddy suggests that when in doubt, rely on your sense of smell:
If other methods fail, give it a sniff. Natural wood emits a pleasant, outdoorsy aroma, while pressure-treated wood carries an oily scent. If the wood lacks an oily smell, it might have been treated with other chemicals, which can produce an unpleasant odor. Another clue is the presence of small, evenly spaced incisions measuring 1/2 to 3/4 inches on all four sides.
Why is this important?
In summary, identifying whether lumber is pressure-treated is crucial for selecting the right wood for a project and ensuring safety. As HomeAdvisor states: “Pressure-treated wood is essential for outdoor projects, while untreated wood is suitable for indoor use. Sawdust from pressure-treated wood can irritate the eyes, skin, and nose.”
