The Simpson Strong-Drive SDCF TIMBER-CF Screw (0.315 in. diameter x 5-1/2 in. length) is a heavy-duty structural fastener engineered specifically for cross-laminated timber construction, mass timber assemblies, and general interior wood applications. Featuring a yellow-zinc coated, fully-threaded shank with a proprietary point design, this screw delivers fast starts and exceptional withdrawal resistance - making it a reliable choice wherever structural performance in CLT and mass timber systems is required. The flat head with underhead nibs countersinks cleanly into wood surfaces, providing a flush, professional finish without surface damage or splintering.

Key Features

• 0.315 in. shank diameter with 5-1/8 in. thread length - full-length threading across nearly the entire fastener body maximizes grip and withdrawal resistance in dense timber applications
• Flat head with underhead nibs - the nibs engage the wood surface as the screw drives home, enabling clean, self-countersinking installation without the need for pre-drilling a countersink recess
• T40 6-Lobe drive type - delivers higher torque transfer with reduced cam-out risk compared to standard Phillips or square drives, keeping installation fast and fatigue-free
• Yellow-zinc coating (fully threaded) - provides corrosion protection suitable for interior and dry-environment use, maintaining fastener integrity over the life of the structure
• Proprietary unique point - designed for fast starts in dense timber materials, reducing splitting and eliminating the need for pilot holes in many applications
• 0.230 in. shank (minor) diameter - optimized shank sizing balances pull-through resistance at the head with the toughness needed to resist shear forces in structural timber connections
• 0.590 in. head diameter - the wide flat head distributes clamping load over a larger bearing area, reducing the risk of pull-through in cross-laminated and mass timber panels

Why This Product

• Engineered from the ground up for CLT and mass timber construction - not a general-purpose wood screw adapted for heavy timber use, but a dedicated structural fastener sized and coated specifically for these demanding applications
• The combination of full-length threading and a proprietary point means the screw resists withdrawal forces along its entire embedded length, which is critical in the large-section timbers common to mass timber building systems
• The self-countersinking flat head with nibs eliminates an extra machining step on the job site, saving time and reducing the chance of surface tear-out on finished CLT panels
• T40 6-Lobe drive compatibility reduces cam-out and stripped drive recesses when driving into dense engineered wood products, keeping installation efficient and reducing bit wear

Specifications

• Brand: Simpson Strong-Tie
• Length: 5-1/2 in.
• Shank Diameter: 0.230 in.
• Head Diameter: 0.590 in.
• Thread Length: 5-1/8 in.
• Head Type: Flat Head with Nibs
• Drive Type: T40 6-Lobe
• Coating: Yellow-Zinc Coated
• Finish: Yellow-Zinc Coated
• Country of Origin: Austria

Available Pack Options

• SDCF22512-R50: 50 Pk - includes one T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)
• SDCF22512: 250 Pk - includes two T40, 6-lobe driver bits (replacement bit: BIT40T-134-R2)

Approved Applications

• Cross-laminated timber (CLT) construction
• Mass timber construction
• General interior structural wood applications
• Interior and dry-environment installations only

Frequently Asked Questions

Is the Strong-Drive SDCF TIMBER-CF screw suitable for outdoor or wet applications?

No. The yellow-zinc coating on this screw is intended for interior and dry applications only. It is not rated for exterior exposure, pressure-treated lumber in wet service conditions, or other environments where sustained moisture is present.

Does this screw require a pilot hole before driving?

The screw features a proprietary unique point designed for fast starts in timber materials, which typically eliminates the need for a pilot hole in many mass timber and CLT applications. Always follow applicable project specifications and engineering requirements for your specific installation.

What bit is needed to drive the Strong-Drive SDCF TIMBER-CF screw?

This screw uses a T40 6-Lobe drive, so a T40 Torx-compatible bit is required. The 6-Lobe profile allows for higher torque transfer and reduces cam-out compared to conventional drive types, which is especially beneficial when driving into dense engineered timber products.

What does "fully threaded" mean for this screw's performance in timber connections?

The 5-1/8 in. thread length runs nearly the full 5-1/2 in. length of the fastener. This means threads engage the wood along almost the entire embedded depth, maximizing withdrawal resistance - the force required to pull the screw out axially - which is a critical performance factor in structural CLT and mass timber connections.