Back to GuidesWoodworking
Heavy-Duty Decking & Outdoor Wood Fastener Selection Guide
Selecting outdoor screws for ACQ pressure-treated lumber and composite decking. Avoid tannin staining, corrosion pitting, and mushrooming on composite boards.
Why Pressure-Treated Wood Destroys Standard Screws
Modern pressure-treated lumber is infused with Alkaline Copper Quaternary (ACQ) chemicals. In the presence of rain and moisture, the high copper concentration aggressively attacks ordinary zinc-plated fasteners, causing structural failures within 1-2 years. Always use 304/316 Stainless Steel or specialized Class 4 Polymer-Coated Deck Screws.