Maintenance Tips: Understanding Treated Lumber
When considering how green your abode is, or will be, it’s always a smart step to know the green qualities of any treated lumber materials that make up your deck and landscape.
Pressure-treated lumber, for instance – once colored with a greenish tint and now colored a reddish brown – has been used for landscaping and decks because of its ability to resist rotting. However, recent health concerns about this popular material have people wanting to know more.
According to Joseph Truini, writing for Popular Mechanics, pressure-treated wood has been around almost 70 years. But not many know how it is made and what chemicals are used to make it rot-resistant.
Pressure-treated boards are rolled into large pressurized tanks where chemical preservatives are forced deep into the wood’s fibers. The resulting product is an exterior-grade wood that’s ideal for building decks, fences, sheds, picnic tables, swing sets, and other outdoor projects.
Chromium Copper Arsenate (CCA) is the basic material used since the 1940s in making the decay-resistant product, at least until 2003. At that time, citing health risks in the arsenic-based product, the EPA halted the production of some pressure-treated wood — the most commonly used material in structures such as decks, play sets, and fences.
Remember the traditional green tint? Now it is reddish brown, meaning it has been treated without arsenate. CCA (Chromated Copper Arsenate) has been replaced with a new preservative, which is copper based — instead of arsenic-based.
Pressure-treated Western red cedar board
Today, you can find pressure-treated lumber treated with numerous inorganic chemicals rather than arsenate. Other common chemicals used are Alkaline Copper Quaternary (ACQ), Copper Azole (CA), Sodium Borate (SBX), and Micronized Copper Quaternary (MCQ). These newer types of treated woods may be less toxic, say experts, but they also contain higher levels of copper, meaning they’re much more corrosive than the old CCA-treated lumber.
Many pressure-treated lumber manufacturers recommend using only stainless steel or hot-dipped galvanized nails, screws, bolts, anchors, and connectors when working with the material. And because these new wood treatments are especially corrosive to aluminum, it’s best to use vinyl or copper flashing, or to wrap the wood in a protective rubberized membrane.
Tips for using PTL
- Wear gloves when handling treated wood, and wash up thoroughly before eating or drinking.
- Always wear safety goggles and a dust mask when cutting, drilling, or sanding.
- Cut treated wood outdoors, not in an enclosed space.
- Never burn treated wood.
- Allow treated wood to dry thoroughly before staining or painting. Test dryness by sprinkling the wood’s surface with water.
- If you don’t stain or paint, apply a clear wood preservative annually to maintain the wood’s water resistance.
- Before driving in a nail or screw, drill a pilot hole to prevent splitting the wood.
- Over time, most treated lumber will shrink slightly across its width as it dries out. Take this small amount of shrinkage into account when laying decking or fence boards.
- After being outdoors for six to 12 months, treated lumber will develop cracks, called “checks,” along the surface of each board. These hairline cracks are a normal part of the drying process.
Tools you will need
- Safety glasses and gloves
- Respirator and mask
- Power saw
- Tape measure
- Thick construction pencil
- Framing square
- Sawhorses
- Wood finish or stain
Photos: Pressure-treated cedar via Shutterstock, wooden floor over forest background via Shutterstock
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