The Simpson Strong-Drive SDCP Timber-CP structural screw is a heavy-duty fastener engineered specifically for cross-laminated timber (CLT) and mass-timber construction, as well as general interior and dry-service applications. Measuring 0.315 inches in overall diameter with a 4-3/4 inch length, this partially threaded screw is designed to draw structural members tightly together, delivering superb holding power and excellent load capacity in wood-to-wood connections, timber framing, and engineered wood assemblies. The yellow-zinc coated finish provides a layer of corrosion resistance suited to interior environments, while the T40 6-Lobe drive system and Type-17 point make installation clean and efficient - typically without the need for predrilling.

Key Features

• Partial Thread Design (3-1/8 in. thread length on a 4-3/4 in. screw) - the unthreaded shank section allows the fastener to pull structural members firmly together, creating tight, gap-free connections in mass timber and engineered wood construction.
• Flat Head with Underhead Nibs - the nibs cut cleanly into the wood surface as the screw seats, allowing the flat head to countersink flush without additional prep work, producing a clean, professional finish.
• T40 6-Lobe Drive Type - provides superior torque transfer and reduces cam-out during driving, giving installers better control and faster, more reliable seating even in dense structural timber.
• Type-17 Cutting Point - the aggressive thread-cutting tip bores into wood fibers efficiently, reducing the need for predrilling and saving significant time on large timber framing and mass-timber projects.
• Yellow-Zinc Coated Finish - offers corrosion resistance appropriate for interior and dry-service environments, helping maintain fastener integrity in protected structural assemblies over the long term.
• 0.575 in. Head Diameter / 0.225 in. Shank Diameter - the generous head diameter distributes clamping load across a wider surface area, while the slender shank minimizes wood splitting in CLT panels, laminated beams, and structural composite lumber.
• Broad Range of Application Coverage - engineered for cross-laminated timber, mass timber, modular construction, post-frame, and general wood framing, making this a single versatile fastener for multiple structural connection types.

Why This Product

• Purpose-Built for Mass Timber and CLT - as CLT and mass-timber construction methods expand across commercial and residential projects, this screw is specifically designed to handle the structural demands of panel-to-beam, panel-to-wall, and multi-ply engineered wood connections where generic fasteners often fall short.
• No Predrilling Typically Required - the Type-17 cutting point eliminates a time-consuming preparatory step on most timber framing and general framing applications, reducing labor time and keeping projects on schedule.
• Clean, Flush Countersinking Without Extra Steps - the flat head combined with underhead nibs seats flush in a single driving motion, which is especially valuable in exposed timber applications where surface appearance matters alongside structural performance.
• Designed for Interior Structural Reliability - rated for interior and dry-service applications, this screw is well-matched to factory-built, modular, and wood residential construction where consistent load performance in a protected environment is the priority.

Specifications

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

Available Pack Options

• SDCP22434-R50: 50 Pk - includes (1) T40, 6-lobe drive bit (replacement bit: BIT40T-134-R2)
• SDCP22434: 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 cutting point is designed to bore into wood fibers efficiently during driving, making it practical for use in cross-laminated timber, mass timber, and general wood framing without a separate predrilling step in most applications.

Is this screw fully threaded or partially threaded?

This is a partially threaded fastener. The thread length is 3-1/8 inches on a 4-3/4 inch screw. The unthreaded shank section is intentional - it allows the screw to draw structural members firmly together, improving clamping performance in wood-to-wood and multi-ply engineered wood connections.

What drive bit does this screw require?

This screw uses a T40 6-Lobe drive, which requires a matching T40 6-Lobe driver bit. The 6-Lobe interface provides excellent torque transfer during driving and significantly reduces cam-out compared to standard drive types, helping seat the screw cleanly in dense structural timber.

What environments and service conditions is this screw rated for?

This screw is designed for interior and dry-service applications. It features a yellow-zinc coated finish suited to protected environments. It is appropriate for cross-laminated timber (CLT), mass timber, engineered wood, structural composite lumber, modular construction, post frame, and general interior wood framing - but is not intended for exterior or high-moisture exposure conditions.

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