Simpson 20d x 4" Preservative-Treated Wood Decking Nail in Type 316 Stainless Steel is a heavy-duty exterior fastener engineered for deck and dock construction where long-term performance in harsh outdoor conditions is essential. Built by Simpson Strong-Tie, this annular-ring shank nail is purpose-designed for use in both green and seasoned preservative-treated pine, delivering the corrosion resistance and withdrawal strength needed to keep outdoor living spaces secure and structurally sound for years to come. The Type 316 stainless steel construction makes it especially well-suited for coastal and high-moisture environments where standard fasteners would quickly degrade.

Key Features

• Type 316 Stainless Steel material - provides superior corrosion resistance against saltwater, moisture, and the harsh chemicals found in preservative-treated lumber, making this nail a reliable choice for seaside decks and exposed dock installations.
• Annular-ring shank - increases withdrawal resistance compared to smooth-shank nails, helping prevent nail heads from popping up over time and maintaining a clean, even deck surface through seasonal changes.
• Larger 0.162" shank diameter (8 gauge) - allows easier penetration into both green and seasoned pressure-treated pine without pre-drilling, saving time during installation while maintaining a strong mechanical connection.
• Full round head with checkered pattern (11/32" diameter) - the checkered surface blends naturally with wood grain texture and reduces glare from sunlight, resulting in a cleaner finished appearance on your deck or dock surface.
• Diamond point tip - self-starting geometry makes driving easier and more accurate, reducing the effort required and helping avoid splitting in dense treated lumber.
• 4" length, 20d penny size - provides the depth of fastening needed for standard decking board thicknesses, ensuring a solid connection to the framing below.
• Made in the United States - domestic manufacturing ensures consistent quality standards throughout production.

Why This Product

• Purpose-built for preservative-treated wood - the larger shank diameter and annular-ring profile are specifically optimized for the density and chemical composition of pressure-treated decking lumber, reducing installation effort while maximizing holding power in real-world outdoor conditions.
• Right material for coastal and wet environments - Type 316 stainless steel offers a step up in corrosion resistance for applications near saltwater, high humidity, or chemical exposure, making it the appropriate choice for docks, waterfront decks, and other demanding outdoor projects.
• Long-term structural integrity - the combination of annular-ring shank geometry and 316 stainless steel means the fastener resists both withdrawal forces and corrosion simultaneously, reducing the likelihood of maintenance callbacks or deck board loosening over time.
• Trusted Simpson Strong-Tie engineering - designed as part of a complete fastener system from a brand known for structural connectors and fasteners, giving builders and homeowners confidence the nail meets the performance expectations of serious exterior construction.

Specifications

• Brand: Simpson Strong-Tie
• Material: Type 316 Stainless Steel
• Finish: Type 316 Stainless Steel
• Penny Size: 20d
• Length: 4 in.
• Gauge: 8
• Shank Diameter: 0.162 in.
• Shank Type: Annular-Ring Shank
• Head Type: Full Round Head
• Head Diameter: 11/32 in.
• Head Pattern: Checkered
• Point Type: Diamond Point
• Approx. Count Per Lb: 40
• Country of Origin: United States

Available Pack Options

• T20PTD1: 1 Lb (40)
• T20PTD5: 5 Lb (200)
• T20PTDB: 25 Lb (1000)

Approved Applications

• Deck construction with preservative-treated lumber
• Dock and pier construction in freshwater and saltwater environments
• Exterior decking projects requiring corrosion-resistant fasteners
• Fastening green or seasoned pressure-treated pine decking boards
• Coastal and high-humidity outdoor applications requiring Type 316 stainless steel performance

Frequently Asked Questions

Why is Type 316 stainless steel recommended for deck and dock projects?

Type 316 stainless steel contains molybdenum, which provides enhanced resistance to saltwater, chemicals, and the corrosive compounds found in preservative-treated lumber. This makes it especially appropriate for coastal decks, waterfront docks, and any outdoor application where prolonged moisture or chemical exposure would cause standard fasteners to corrode and fail prematurely.

What does the annular-ring shank do compared to a smooth-shank nail?

The annular-ring shank features rings along the shank that grip the wood fibers as the nail is driven, significantly increasing withdrawal resistance. This means the nail is far more resistant to being pulled back out over time - reducing the chance of nail heads popping up above the deck surface due to seasonal wood movement, foot traffic, or loading.

Can this nail be used in both green and kiln-dried pressure-treated lumber?

Yes. The larger 0.162" shank diameter is specifically designed to allow easy installation into both green (wet, freshly treated) and seasoned (dried) preservative-treated pine, so it performs reliably regardless of the moisture content of the lumber at the time of installation.

What does the checkered head pattern on this decking nail do?

The checkered pattern on the full round head serves two practical purposes: it blends visually with the wood grain texture of decking boards for a more finished appearance, and it reduces glare from sunlight reflecting off the nail head - both of which contribute to a cleaner, more professional-looking deck surface.

Note: Product dimensions may differ from picture.