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 wood-to-wood fastening applications. This 0.315" diameter, 5-1/2" long partially threaded screw features a yellow-zinc coated finish, a T40 6-lobe drive, and a flat head with underhead nibs that delivers clean, flush countersinking without the need for a separate pilot hole in most installations. Designed by Simpson Strong-Tie to pull structural members together with superb holding power and excellent load capacity, it is well-suited for timber framing, engineered wood assemblies, multi-ply fastening, post frame construction, and modular building projects.

Key Features

• Partially Threaded Shank (3-1/8" thread length) - the unthreaded section creates a clamping action that draws structural members tightly together, maximizing holding power and load capacity in timber connections.
• Flat Head with Underhead Nibs - the nibs score the wood surface as the screw seats, allowing the head to countersink cleanly and flush without the need for a countersink bit, saving installation time and producing a professional finish.
• T40 6-Lobe Drive - provides high torque transfer with reduced cam-out risk, giving installers greater control and driving efficiency even in dense or engineered timber materials.
• Type-17 Point - the aggressive cutting tip evacuates waste material as the screw drives in, reducing splitting and typically eliminating the need for predrilling in most applications.
• Yellow-Zinc Coated Finish - provides corrosion resistance appropriate for interior and dry-service environments, protecting the fastener throughout the service life of the structure.
• 0.315" Shank Diameter with 0.575" Head Diameter - the robust shank delivers structural-grade strength, while the wide head distributes load across a larger bearing surface for superior pull-through resistance.
• 5-1/2" Length - offers substantial penetration depth for solid timber-to-timber connections, ledger attachments, and multi-ply engineered wood assemblies.

Why This Product

• Purpose-built for CLT and mass-timber construction where reliable structural connections are critical - the partial thread design pulls members tight while the large flat head resists pull-through under load.
• No predrilling is typically required thanks to the Type-17 cutting point, which reduces labor time and speeds up installation on timber framing, post frame, and general framing projects.
• The T40 6-lobe drive works efficiently in high-torque applications, helping installers drive through thick timber sections with better control and less driver slippage than standard drive types.
• Broad application compatibility - from floor-to-floor connections and panel-to-beam fastening to structural composite lumber and factory-built modular construction - means fewer fastener SKUs to manage on complex job sites.

Specifications

• Brand: Simpson Strong-Tie
• Length: 5-1/2 in.
• Shank Diameter: 0.225 in.
• Head Diameter: 0.575 in.
• Thread Length: 3-1/8 in.
• Head Type: Flat Head with Nibs
• Drive Type: T40 6-Lobe
• Point Type: Type-17 Point
• Finish: Yellow-Zinc Coated
• Coating: Yellow-Zinc Coated
• Service Condition: Interior and dry-service applications
• Country of Origin: Taiwan

Available Pack Options

• SDCP22512-R50: 50 Pk - includes (1) T40, 6-lobe drive bit (replacement bit: BIT40T-134-R2)
• SDCP22512: 250 Pk - includes (2) T40, 6-lobe drive bits (replacement bit: BIT40T-134-R2)

Approved Applications

• Mass Timber / Cross-Laminated Timber (CLT) Construction
• Timber Framing
• General Framing - Wood
• Engineered Wood Fastening
• Engineered Wood - Multi-Ply Fastening
• Structural Composite Lumber
• Fastening Wood-to-Wood
• Fastening Floor-to-Floor
• Post Frame Construction
• Factory-Built / Modular Construction
• 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 evacuate wood material as the screw drives in, reducing the risk of splitting and allowing direct installation into most timber and engineered wood substrates without a pilot hole.

Is this screw suitable for outdoor or wet environments?

No - the SDCP Timber-CP screw with yellow-zinc coating is intended for interior and dry-service applications only. It is not rated for exterior, pressure-treated lumber, or high-moisture environments.

What is the purpose of the partial thread design on this screw?

The partial thread - 3-1/8" of threading on a 5-1/2" screw - leaves an unthreaded shank section between the head and the threads. This design allows the unthreaded portion to pass freely through the top member while the threads bite into the bottom member, creating a clamping effect that pulls the two structural members tightly together for a stronger, tighter connection.

What driver bit does this screw require?

This screw requires a T40 6-lobe (Torx-style) driver bit. The T40 6-lobe interface is designed to handle high torque loads with reduced cam-out, making it well-suited for driving into dense timber materials used in CLT and mass-timber construction.

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