The Simpson Strong-Drive SDCP TIMBER-CP Screw is a high-performance structural fastener engineered for cross-laminated timber (CLT) and mass-timber construction, as well as general interior and dry-service applications. Featuring a T40 6-Lobe drive and a Type-17 point, this 0.315-inch diameter, 3 1/8-inch long screw is designed to pull structural wood members tightly together - delivering superb holding power and excellent load capacity without the need for predrilling in most applications. The yellow-zinc coating provides corrosion resistance suited for interior environments, making it a reliable choice for timber framing, engineered wood assemblies, and factory-built or modular construction.

Key Features

• Flat Head with Underhead Nibs - enables clean, flush countersinking into wood surfaces for a professional finish and tight member-to-member contact
• T40 6-Lobe Drive - delivers high torque transfer with reduced cam-out risk, improving installation speed and reducing driver wear during heavy framing work
• Type-17 Point - cuts through wood fibers cleanly, minimizing splitting and reducing the need for predrilling in most cross-laminated timber and mass-timber applications
• Partial Thread Design (2-inch thread length on a 3 1/8-inch screw) - the unthreaded shank spans across the joint, allowing the threads to engage only the receiving member and draw structural components firmly together
• Yellow-Zinc Coated Finish - provides corrosion resistance appropriate for interior and dry-service structural applications, helping maintain long-term fastener integrity
• Broad Application Range - suitable for CLT panels, mass-timber connections, engineered wood, structural composite lumber, and general wood framing - reducing the need for multiple fastener types on a single jobsite
• 0.575-inch Head Diameter - large bearing surface distributes load effectively across the wood surface, enhancing holding power in panel-to-panel and panel-to-beam connections

Why This Product

• Specifically engineered for CLT and mass-timber construction - where standard wood screws often lack the structural capacity needed for multi-ply panel assemblies, lap joints, and panel-to-beam connections
• The partial thread geometry actively pulls members together as the screw is driven, eliminating gaps between structural layers without the extra step of clamping - a real time-saver on timber framing projects
• Predrilling is not typically required, which reduces labor and equipment needed on-site, making this screw practical for general framing, post frame, and factory-built construction workflows
• The T40 6-Lobe drive paired with the Type-17 point means fewer stripped fasteners and cleaner installation even in dense engineered wood products like structural composite lumber and multi-ply engineered wood assemblies

Specifications

• Brand: Simpson Strong-Tie
• Length: 3 1/8 in.
• Shank Diameter: 0.225 in.
• Head Diameter: 0.575 in.
• Thread Length: 2 in.
• Drive Type: T40 6-Lobe
• Head Type: Flat Head with Nibs
• Point Type: Type-17 Point
• Finish: Yellow-Zinc Coated
• Coating: Yellow-Zinc Coated
• Country of Origin: Taiwan

Available Pack Options

• SDCP22318-R50: 50 Pk - includes (1) T40, 6-lobe drive bit (replacement bit: BIT40T-134-R2)
• SDCP22318: 250 Pk - includes (2) T40, 6-lobe drive bits (replacement bit: BIT40T-134-R2)

Approved Applications

• Engineered Wood
• Fastening Wood-to-Wood
• Timber Framing
• Factory-Built/Modular Construction
• General Framing
• Post Frame
• Framing - Wood
• Mass Timber / Cross-Laminated Timber
• Fastening Floor-to-Floor
• Engineered Wood - Multi-Ply Fastening
• Structural Composite Lumber
• Wood / Residential Construction

Frequently Asked Questions

Does this screw require predrilling before installation?

Predrilling is not typically required. The Type-17 point is designed to cut through wood fibers cleanly, reducing splitting risk and allowing direct installation into cross-laminated timber, mass-timber panels, and other engineered wood products in most situations.

Why is this screw only partially threaded?

The 2-inch thread length on this 3 1/8-inch screw is intentional. With a partial thread design, the unthreaded shank passes through the first structural member without gripping it, while the threads engage only the receiving member. This pulls the two components tightly together, eliminating gaps - which is critical for structural connections in CLT and mass-timber assemblies.

What service conditions is this screw rated for?

This screw with its yellow-zinc coating is designed for interior and dry-service applications. It is not intended for exterior, wet, or pressure-treated lumber environments where higher corrosion resistance would be required.

What drive bit is needed to install this screw?

This screw uses a T40 6-Lobe drive, so a T40 6-Lobe (Torx-style) driver bit is required for installation. The T40 size is matched to the screw's diameter and is selected to handle the higher torque demands of structural timber fastening applications.

Note: Product dimensions and/or thread length may differ from picture. Please see item description for specifications.