Pressure treated wood is primarily protected against insects and rot.
Pressure treatment is a process where wood is placed in a closed cylinder and a liquid chemical preservative is forced into the wood fibers under pressure. This process penetrates the wood much deeper than surface application, providing long-lasting protection against common threats that can significantly reduce the lifespan of untreated wood, especially in outdoor or damp environments.
Core Protection
As stated in a reference from August 1, 2023, while pressure treatment protects against insects and rot, sealing is necessary to protect the wood from moisture and mildew. This highlights the two primary enemies that pressure treatment is specifically designed to combat.
Protection Against Insects
Wood is a food source and habitat for various insects that can cause structural damage. Pressure treatment injects chemicals that are toxic or repellent to these pests.
- Termites: These are perhaps the most well-known wood-destroying insects, capable of hollowing out structures. Pressure treatment makes the wood unpalatable and toxic to termites.
- Carpenter Ants: While they don't eat wood, carpenter ants bore tunnels in it to build nests, compromising its integrity. The chemicals deter nesting.
- Wood Boring Beetles: Various beetle species lay eggs in wood, and their larvae tunnel extensively as they mature. Pressure treatment prevents infestation.
Protection Against Rot
Rot is caused by fungal organisms that break down the cell walls of wood, leading to decay and loss of strength. Fungi thrive in damp conditions.
- Fungal Decay: Pressure treatment saturates the wood with fungicides that prevent the growth and spread of these decay-causing fungi. This is crucial for wood in contact with the ground or exposed to constant moisture.
What Pressure Treatment Doesn't Protect Against
It's important to note the limitations of pressure treatment. As the reference points out, while pressure treatment protects against insects and rot, sealing is necessary to protect the wood from moisture and mildew.
- Moisture: Pressure treatment doesn't make the wood waterproof. Wood can still absorb water, which can lead to swelling, shrinking, cracking, and warping over time.
- Mildew: Mildew is a surface-level mold that can grow on damp wood. While not as structurally damaging as rot, it is unsightly and can indicate underlying moisture issues. Sealing and periodic cleaning are needed to prevent mildew.
- UV Damage: Sunlight can cause the wood surface to gray and degrade over time. Pressure treatment offers no protection against UV radiation.
Why This Protection Matters
The protection pressure treatment offers is essential for the longevity and structural integrity of exterior wood structures. For example, softwoods like pine and cedar are commonly used deck-building materials in the United States, as mentioned in the reference. These woods, while affordable and easy to work with, are naturally susceptible to insects and rot. Pressure treating them significantly extends their usable life, making them suitable for decks, fences, pergolas, and other outdoor applications where they are exposed to environmental threats.
The increased durability provided by pressure treatment reduces the need for frequent repairs or replacement, saving time and money in the long run.
Here's a quick summary:
| Pressure Treatment Protects Against | Needs Additional Protection Against |
|---|---|
| Insects (Termites, Carpenter Ants, etc.) | Moisture |
| Fungal Rot (Decay) | Mildew |
| UV Damage |
