The Simpson Strong-Drive SDCP Timber-CP Screw is a heavy-duty structural fastener engineered for cross-laminated timber (CLT) and mass-timber construction, as well as a wide range of general interior wood-to-wood applications. Measuring 0.315 in. in overall diameter with an 11-3/4 in. length, this partially threaded screw pulls structural members together with superb holding power and excellent load capacity. The yellow-zinc coated finish provides a durable surface layer suited for dry-service and interior environments. Whether you are working on timber framing, engineered wood assemblies, or modular construction projects, this screw delivers consistent, reliable performance without the need for predrilling in most applications.

Key Features

• Flat Head with Underhead Nibs - the nibs bite into the wood surface during installation, enabling clean, flush countersinking without a separate countersink step, resulting in a smooth, professional finish.
• T40 6-Lobe Drive - provides high torque transfer and positive bit engagement, reducing cam-out and driver slip during high-load structural fastening.
• Partial Threading with 3-1/8 in. Thread Length - draws structural members tightly together by allowing the unthreaded shank to pass freely through the first member, creating strong clamping force between timber panels and beams.
• Type-17 Point - the self-drilling point bores into dense wood fibers cleanly, meaning predrilling is not typically required even in thick mass-timber assemblies, saving installation time.
• Yellow-Zinc Coated Finish - protects the fastener surface in dry-service and interior applications, maintaining structural integrity over time in controlled environments.
• 0.575 in. Head Diameter - the large bearing surface distributes load across a wider area, improving pullthrough resistance and overall holding power in structural connections.
• 0.225 in. Shank Diameter - sized for structural load ratings in CLT, mass timber, and engineered wood assemblies, providing a robust cross-section for shear and withdrawal demands.
• Broad Application Range - designed for cross-laminated timber, structural composite lumber, post frame, general framing, and engineered wood multi-ply fastening, making it a versatile choice across multiple project types.

Why This Product

• Specifically engineered for cross-laminated timber and mass-timber construction - a growing segment of modern structural building where precise clamping force, flush installation, and high load capacity are critical requirements that general-purpose screws often cannot meet.
• The combination of partial threading and a large flat head with nibs eliminates the need for separate countersinking and pre-boring steps in most installations, reducing labor time and simplifying the fastening process on engineered wood panels and timber frames.
• At 11-3/4 in. long, this screw reaches deep into thick timber assemblies - ideal for panel-to-beam, lap joint, ledger, and surface spline connections where shorter fasteners would fail to achieve adequate embedment depth.
• The T40 6-lobe drive system is designed to handle the high installation torque demands of dense mass timber and structural composite lumber, giving installers confident, slip-free driving even in challenging field conditions.

Specifications

• Brand: Simpson Strong-Tie
• Coating: Yellow-Zinc Coated
• Finish: Yellow-Zinc Coated
• Length (in.): 11 3/4
• Head Diameter (in.): 0.575
• Shank Diameter (in.): 0.225
• Drive Type: T40 6-Lobe
• Head Type: Flat Head with Nibs
• Thread Length (in.): 3 1/8
• Point Type: Type-17 Point
• Country of Origin: Taiwan

Available Pack Options

• SDCP221134-R50: 50 Pk - includes (1) T40, 6-lobe drive bit (replacement bit: BIT40T-134-R2)
• SDCP221134: 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 bore into wood fibers cleanly on its own, making installation faster and more straightforward in cross-laminated timber, mass timber, and engineered wood assemblies without a separate drilling step.

What drive bit does this screw use?

This screw uses a T40 6-lobe drive. The 6-lobe geometry allows for high torque transfer and positive bit engagement, which is especially important when driving long structural screws into dense timber materials where cam-out can be a concern.

Why is this screw only partially threaded?

The partial threading - with a 3-1/8 in. thread length on an 11-3/4 in. screw - is intentional for structural clamping performance. The unthreaded shank passes freely through the first member, while the threads engage only the second member, pulling both pieces tightly together. This design is specifically suited for CLT panels, timber-to-beam connections, and other mass-timber structural assemblies.

Is this screw suitable for outdoor or wet-service applications?

No. The yellow-zinc coated finish on this screw is intended for interior and dry-service applications only. It is not rated for exterior, high-humidity, or pressure-treated lumber environments where a corrosion-resistant coating such as stainless steel or hot-dip galvanizing would be required.

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