The Simpson Strong-Drive SDCF Timber-CF Screw (0.315 x 13-3/4 in.) is a heavy-duty structural fastener engineered specifically for cross-laminated timber (CLT) construction, mass timber assemblies, and general interior structural applications. With a 0.315 in. diameter and 13-3/4 in. length, this fully-threaded, yellow-zinc coated screw delivers exceptional withdrawal resistance and load-bearing performance where structural integrity cannot be compromised. The proprietary point geometry ensures fast, consistent starts even in dense timber, while the flat head with underhead nibs seats cleanly and flush without surface tearing - making it a top choice for architects and contractors working on modern mass timber projects.

Key Features

• Yellow-zinc, fully-threaded design - provides excellent withdrawal resistance along the entire 13-3/8 in. thread length, maximizing holding power in CLT and mass timber connections
• Flat Head with underhead nibs (0.590 in. head diameter) - nibs bite into the wood surface during installation for clean, flush countersinking without pre-drilling a countersink, saving installation time
• Proprietary unique point geometry - enables fast starts and reduces splitting in dense timber, improving installation speed and accuracy
• T40 6-Lobe drive type - delivers high torque transfer with reduced bit cam-out, so installers maintain better control on long, deep drives through thick timber members
• 0.315 in. shank diameter with 0.230 in. shank body - engineered for structural shear and withdrawal loads in demanding timber framing applications
• Yellow-zinc coating finish - protects the fastener during handling and installation in dry interior environments where moisture exposure is not a concern

Why This Product

• Designed from the ground up for cross-laminated timber and mass timber construction - these are structural demands that standard wood screws are not rated to handle, and the SDCF Timber-CF screw is purpose-built to meet them
• The fully-threaded shank paired with the proprietary point means the screw achieves deep, consistent engagement across the full 13-3/8 in. thread length, translating directly to stronger, more reliable connections in beam reinforcement and butt joist fastening
• The flat head with nibs eliminates the need for a separate countersink operation, reducing labor steps when fastening wall-to-wall assemblies or support beams where a clean, flush surface matters
• The T40 6-Lobe drive resists cam-out during the long drive required for 13-3/4 in. penetration, giving installers consistent, fatigue-reducing performance across high-volume mass timber projects

Specifications

• Brand: Simpson Strong-Tie
• Length (in.): 13 3/4
• Shank Diameter (in.): 0.230
• Head Diameter (in.): 0.590
• Thread Length (in.): 13 3/8
• 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

• SDCF221334-R50: 50 Pk - includes one T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)
• SDCF221334: 250 Pk - includes two T40, 6-lobe driver bits (replacement bit: BIT40T-134-R2)

Approved Applications

• Beam Reinforcement
• Fastening Support Beams
• Fastening Wall-to-Wall
• Fastening Butt Joists
• Mass Timber / Cross-Laminated Timber

Frequently Asked Questions

Is this screw suitable for outdoor or wet environments?

No. The Simpson Strong-Drive SDCF Timber-CF screw with yellow-zinc coating is designed for interior and dry applications only. It is not rated for outdoor, exposed, or high-moisture environments.

What drive bit do I need to install this screw?

This screw requires a T40 6-Lobe bit. The 6-lobe drive design is specifically chosen to handle the high torque needed for driving a 13-3/4 in. structural screw through dense timber while minimizing cam-out and bit wear.

Why does this screw have a flat head with nibs rather than a standard flat head?

The underhead nibs on the flat head are designed to cut into the wood surface as the screw seats, allowing the head to countersink cleanly and flush without requiring a pre-drilled countersink hole. This is particularly useful in mass timber and CLT applications where a smooth, finished surface is important.

What makes this screw appropriate for cross-laminated timber and mass timber construction?

The SDCF Timber-CF screw features a 0.315 in. diameter, a fully-threaded shank with 13-3/8 in. of thread engagement, and a proprietary point that provides fast starts and excellent withdrawal resistance. These characteristics are engineered specifically to meet the structural demands of CLT, mass timber connections, beam reinforcement, and butt joist fastening in interior structural assemblies.