Simpson Strong-Drive SDCF TIMBER-CF Screw (0.315" x 11-3/4") is a heavy-duty structural fastener engineered specifically for cross-laminated timber (CLT) construction, mass timber framing, and general interior wood applications. Manufactured by Simpson, this fully-threaded yellow-zinc coated screw delivers exceptional withdrawal resistance and clean, precise countersinking - making it a trusted choice for structural timber connections where strength and performance cannot be compromised.

Key Features

• 0.315" screw diameter with 0.230" shank diameter - provides the structural rigidity needed for demanding timber-to-timber connections without splitting the wood during installation
• Yellow-zinc coating on a fully-threaded shank - protects against corrosion in interior and dry environments while ensuring consistent thread engagement along the full 11-3/8" thread length for superior holding power
• Flat head with underhead nibs - the 0.590" head diameter combined with nibs beneath the head allows the screw to countersink cleanly and flush into timber surfaces, leaving a professional finish
• Proprietary unique point design - engineered for fast starts and self-drilling entry into dense timber materials, reducing labor time and pre-drilling requirements
• T40 6-Lobe drive type - provides high torque transfer and reduces cam-out during installation, keeping the driver engaged even under the high rotational force required for mass timber work
• 11-3/4" overall length with 11-3/8" thread length - maximizes thread engagement depth in thick timber members, translating directly into excellent axial withdrawal resistance

Why This Product

• Designed from the ground up for cross-laminated timber and mass timber construction - this screw addresses the specific fastening demands of engineered wood panels where standard fasteners often fall short in withdrawal performance
• The fully-threaded shank running nearly the entire 11-3/4" length means thread engagement begins immediately and continues deep into the receiving member, maximizing resistance to pull-out forces in structural applications
• The T40 6-Lobe drive system reduces installation fatigue and tool slippage compared to conventional drive styles, making it a practical choice for high-volume timber framing work
• The yellow-zinc coating and flat-head-with-nibs design combine a clean countersunk appearance with surface protection suited to interior and dry-service structural connections

Specifications

• Brand: Simpson Strong-Tie
• Screw Diameter (in.): 0.315
• Shank Diameter (in.): 0.230
• Length (in.): 11-3/4
• Thread Length (in.): 11-3/8
• Head Diameter (in.): 0.590
• Head Type: Flat Head with Nibs
• Drive Type: T40 6-Lobe
• Coating/Finish: Yellow-Zinc Coated
• Country of Origin: Austria

Available Pack Options

• SDCF221134-R50: 50 Pk - includes one T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)
• SDCF221134: 250 Pk - includes two T40, 6-lobe driver bits (replacement bit: BIT40T-134-R2)

Approved Applications

• Cross-laminated timber (CLT) construction
• Mass timber construction and framing
• General interior structural wood connections
• Dry-service applications only - not for use in wet or exterior environments

Frequently Asked Questions

Is this screw suitable for outdoor or wet environments?

No. The Strong-Drive SDCF TIMBER-CF screw with yellow-zinc coating is designed for interior and dry applications only. It is not rated for exterior, wet, or high-humidity environments.

Does this screw require pre-drilling before installation?

The screw features a proprietary unique point designed to provide fast starts and self-drilling entry into timber materials. This point design is engineered to reduce or eliminate the need for pre-drilling in typical mass timber and cross-laminated timber applications.

What driver bit is needed for this screw?

This screw uses a T40 6-Lobe drive type. A T40 Torx or 6-lobe bit is required to properly install this fastener and take advantage of its high torque transfer and reduced cam-out characteristics.

What makes this screw appropriate for mass timber and CLT construction?

The screw's 0.315" structural diameter, near-full-length threading (11-3/8" of thread on an 11-3/4" screw), and proprietary point work together to deliver excellent withdrawal resistance - a critical requirement in cross-laminated timber and mass timber structural connections. The flat head with underhead nibs also allows it to countersink cleanly into engineered wood panel surfaces.