Wood is treated for outdoor use primarily through pressure treatment to protect it from rot, decay, and insect infestation.
Here's a breakdown of common wood treatment methods:
Pressure Treatment
Pressure treatment is the most common method for treating wood for outdoor applications. The process involves forcing preservatives deep into the wood fibers.
- Process: The wood is placed in a large, sealed cylinder. Air is removed to create a vacuum. The cylinder is then flooded with a preservative solution under high pressure, forcing the chemicals deep into the wood's cells.
- Preservatives: Common preservatives include:
- ACQ (Alkaline Copper Quaternary): A copper-based preservative effective against fungi and insects.
- CA (Copper Azole): Another copper-based preservative, considered a more environmentally friendly alternative.
- Micronized Copper Azole (MCA): A variation of CA using smaller copper particles, allowing for better penetration and a lighter color.
- Benefits:
- Long-lasting protection against rot, decay, and insects.
- Increased lifespan of the wood.
- Suitable for a wide range of outdoor applications, including decks, fences, and landscaping timbers.
Other Treatment Methods
While pressure treatment is the most prevalent, other methods exist.
- Borate Treatment: This involves using borate compounds to protect wood against insects and decay. Borate-treated wood is typically used in areas not directly exposed to rain or ground contact.
- Heat Treatment: Some woods are heat-treated to improve their resistance to decay. This process alters the wood's cellular structure, making it less appealing to fungi.
- Oil-Based Preservatives: These penetrate the wood and create a water-repellent barrier, helping to prevent rot and decay. They often contain fungicides and insecticides.
- Surface Applications: Applying paints, stains, or sealants to wood can offer some protection against the elements, but this method typically requires regular reapplication.
Considerations
- Type of Wood: Different wood species have varying natural resistance to decay. Some naturally durable woods, like cedar and redwood, require less treatment than others.
- Application: The intended use of the wood will determine the appropriate level of treatment needed. Ground contact applications require a higher level of protection.
- Safety: Always follow manufacturer's instructions when working with treated wood and wear appropriate personal protective equipment.
Pressure treatment significantly extends the life of wood used outdoors, making it a durable and reliable building material.
