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 general interior and dry-service applications. This partially threaded, yellow-zinc coated screw is purpose-built to draw structural members firmly together, delivering superb holding power and excellent load capacity in demanding wood-to-wood connections. The 0.315 in. nominal diameter and 8-5/8 in. length make it well suited for thick engineered wood assemblies, timber framing, and multi-ply fastening where depth and clamping strength are critical. With a Type-17 point designed to pierce wood cleanly, predrilling is not typically required, saving time on the job site.

Key Features

• Partially threaded design with 3-1/8 in. thread length - concentrates clamping force at the joint interface, pulling structural members tightly together for maximum holding power in timber connections
• Yellow-zinc coated finish - provides corrosion resistance suitable for interior and dry-service environments, helping the fastener maintain integrity over the life of the structure
• Flat head with underhead nibs (0.575 in. head diameter) - the nibs cut cleanly into the wood surface as the screw seats, allowing flush, clean countersinking without the need for a countersink bit
• T40 6-Lobe drive type - delivers high torque transfer with reduced cam-out compared to standard drives, giving installers better control and a cleaner drive even in dense timber
• Type-17 point - self-piercing tip bores into wood fiber efficiently, so predrilling is not typically required, reducing installation steps in mass-timber and engineered wood assemblies
• 0.225 in. shank diameter - a slender shank relative to the thread diameter helps reduce splitting pressure while the threads maintain strong purchase in structural lumber and engineered wood products
• Broad length range availability - the SDCP line is available in a wide range of lengths, giving builders the flexibility to select the right fastener depth for each specific structural application

Why This Product

• Engineered for CLT and mass-timber construction - as cross-laminated timber and mass-timber building methods grow in commercial and residential projects, having a structural screw specifically designed for these assemblies means fewer callbacks and connections that perform to engineering specifications.
• No predrilling typically required - the Type-17 self-piercing point eliminates a separate drilling step in most applications, speeding up installation in timber framing, post-frame, and modular construction workflows.
• Flush countersinking without extra tooling - the flat head with integrated underhead nibs seats cleanly at or below the wood surface, creating a professional finish in exposed panel-to-beam and surface spline connections without a countersink bit.
• Versatile across structural wood applications - from floor-to-floor fastening and ledger connections to structural composite lumber and multi-ply engineered wood, a single screw size covers a wide range of connections, simplifying material planning on complex timber projects.

Specifications

• Brand: Simpson Strong-Tie
• Coating: Yellow-Zinc Coated
• Finish: Yellow-Zinc Coated
• Length (in.): 8-5/8
• 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

• SDCP22858-R50: 50 Pk - includes (1) T40, 6-lobe drive bit (replacement bit: BIT40T-134-R2)
• SDCP22858: 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

Do I need to predrill before installing the Simpson Strong-Drive SDCP Timber-CP screw?

Predrilling is not typically required. The Type-17 point is designed to pierce wood fiber efficiently on its own, which simplifies installation in mass-timber, CLT, and engineered wood assemblies and reduces the number of steps needed to complete each connection.

What drive bit does this screw require?

This screw uses a T40 6-Lobe drive. The 6-lobe geometry provides high torque transfer and reduces cam-out during installation, which is particularly beneficial when driving larger-diameter structural screws into dense timber members.

Is this screw suitable for outdoor or pressure-treated lumber applications?

The SDCP Timber-CP screw with yellow-zinc coating is rated for interior and dry-service applications only. It is not intended for exterior exposure, wet-service conditions, or use with pressure-treated lumber where a corrosion-resistant coating would be required.

What does the partial thread design mean for structural performance?

Because only 3-1/8 in. of the 8-5/8 in. length is threaded, the unthreaded shank passes freely through the top member while the threads engage the receiving member below. This allows the screw to act as a clamp, drawing the two structural members tightly together at the joint interface for a strong, secure timber connection.

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