If you are considering the addition of an outdoor living structure you have probably heard the term “pressure-treated wood” quite frequently. In case you are not familiar with the product, or the process, you may be wondering what is the difference between pressure- treated wood and regular wood? In the world of outdoor living structures, there are a myriad of materials to choose from when considering a deck or porch. It can be a daunting task to try to figure out the characteristics of these materials. Since pressure-treated wood, and more commonly pressure-treated pine, is used heavily in outdoor construction, Archadeck of Central SC felt it appropriate to explain what the product is, how it is made, and what it is used for.
The history of wood preservation
The theory behind pressure-treated wood is based on preservation of the wood to gain the most benefit and longevity. The practice of preserving wood is nothing new and spans all the way back to the history of the use of wood itself. There are records of wood preservation in ancient Greece during Alexander the Great’s rule, where bridge wood was soaked in olive oil in an effort to preserve it. The Romans protected their ship hulls by brushing the wood with tar. During the Industrial Revolution wood preservation became a cornerstone of the wood processing industry.
What is pressure treatment?
With pressure-treated pine, the wood is placed in a pressurized cylinder and a solution of Micronized Copper Azole (MCA) is forced into the wood, leaving a very slight greenish color. When pressure-treated pine is new, it is so full of fluid that it will feel wet and heavy. Over time the liquid evaporates but the chemical still protects the wood. Pressure treatment, in essence, is the process that forces chemical preservatives into the wood. The preservatives help protect the wood from attack by termites, other insects, and fungal decay.
Builders in the outdoor structure and decking industry continue to rely on pressure-treated wood, but often it is not the same treated wood as was used in the past. According to the North American Decking and Remodeling Association, (NADRA), for the past 40 years, the predominant chemical for preserving lumber was Chromated Copper Arsenate (CCA). While this preservative remains the usual choice for heavy-duty construction, newer alternatives have replaced CCA for decks and non-industrial applications. Primary among these are (1) Copper Azole and (2) Alkaline Copper Quaternary. Both are combinations of copper and a carbon-based co-biocide. In North America, wood treated with copper azole is called Wolmanized® or Outdoor® wood. Lumber treated with alkaline copper quaternary is sold under several brands. These preservatives mark a trend to treatments involving less chemical and, notably, less metal. Farthest ahead of this movement is Wolmanized® L3 wood. Suitable for out-of-ground applications, it is the first non-metallic preservative for residential uses.
In the Eastern US, where pressure-treated lumber has been used for decades, Southern pine is the most commonly treated species. One of the main reasons for using pine is although it is light, it is very strong. Pine is easier to process than other woods and readily accepts treatment. The nature of the way pine grows is perfect for decks and other outdoor structures. Pine grows in a straighter fashion than other woods and therefore will hold a straight line very well.
Despite all the competition, pressure-treated wood is still the number one decking material sold today. Nearly 75% of all new decks are finished with pressure-treated lumber. The widespread popularity of pressure-treated lumber is not surprising: it’s affordable, readily available coast-to-coast, structurally strong and easy to cut and to fasten with screws.
Keep in mind that most outdoor structures are built with pressure-treated pine framing, including structures finished out with low-maintenance materials such as composites. Pressure-treated framing is used so the structure does not rot over time, and also so the termites will not eat it. There are other natural woods here in the US that can be used for framing purposes, but they cost significantly more and deliver the same results as pressure-treated wood.
Pressure Treated Care
Even though wood goes through the pressure treatment process to ensure decreased degradation and resistance to termites, this process does not mean no additional care or maintenance is needed to keep these qualities. Archadeck of Central SC recommends regular maintenance. Maintenance includes initial staining and sealing followed by frequent cleaning along with more staining and sealing as needed. We recently outlined the best way to care for your pressure treated deck in a post titled “Archadeck of Central SC shows you how to protect your wooden outdoor living investment.” That article is loaded with helpful information regarding the care and maintenance of pressure treated pine and other natural wood components used on our outdoor structures.
Before you can stain and seal your pressure-treated wood deck, you will need to let the wood dry. For new decks, depending on the amount of sun exposure, this drying out period will vary. This also depends on how dry your decking boards are when installed and how much rain you have had recently. Before initial staining and sealing, splash a little water on the wood; if it beads versus penetrating, the wood is too wet. When water penetrates versus beading, the stain will penetrate as well.
Traditional wooden decks, such as those built using pressure-treated pine, offer a beautiful natural appearance. Archadeck of Central SC can help explore all your material options for your anticipated project while keeping your budget and personal tastes in mind. Please contact us today to learn more. (803) 603 – 2160 or