Do You Need Special Screws for Pressure-Treated Wood?

Introduction

Most rot-resistant pressure-treated lumber sold for homeowner use relies on two popular copper-based wood preservatives - alkaline copper quaternary (ACQ) and copper azole. While these newer wood preservatives offer better rot protection compared to the arsenic-based compounds they replaced, they can cause rapid corrosion of ordinary steel screws, nails, or bolts, leading to early structural failure. Therefore, it is essential to use corrosion-resistant fasteners designed for copper-treated wood.

Galvanized Steel Fasteners

One effective and cost-effective solution for using pressure-treated wood is galvanized steel fasteners. These are made by hot-dipping steel screws, nails, and bolts in molten zinc at 850 degrees Fahrenheit. Galvanized fasteners must meet specific quality and coating standards:

ASTM A153 for zinc coating quality G-185 for the amount of zinc coating The G-185 coating is equivalent to 1.85 ounces of zinc per square foot of steel

Galvanized fasteners are not only effective but also relatively inexpensive compared to stainless steel options. However, it is crucial to understand that they must be used with appropriate connectors to ensure safety and structural integrity.

Stainless Steel Fasteners

For even greater corrosion resistance, stainless steel fasteners in grades 304 and 305 are recommended for most areas, while grade 316 is better suited for coastal regions due to its enhanced resistance to salt and moisture.

While stainless steel fasteners offer longer-lasting solutions, they come with higher costs, often ranging from five to ten times more expensive than galvanized fasteners. Additionally, they cannot be used with galvanized structural connectors as these materials can react adversely, leading to further corrosion and potential structural failures.

In summary, when working with pressure-treated wood, it is crucial to choose the right type of fastener to ensure durability and longevity of your projects. By understanding the properties and applications of both galvanized and stainless steel fasteners, you can make informed decisions and achieve the best results.

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Topics: Pressure-treated wood, Copper-based wood preservatives, Corrosion-resistant fasteners, Galvanized steel screws, Stainless steel screws, Wood preservation, Structural failure, Woodworking projects