Flat Washer Head Partially Threaded Self-Tapping Structural Wood Screw
  • Code Approval
  • ICC, ETA
  • Connection Type
  • Wood/Wood
  • Applications
  • Timber Framing, Log Home Building, Mass & Heavy Timber Construction
  • Manufacturer
  • SWG

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Flat Washer Head

Shank Cutter

Partially Threaded

Counter Thread Tip

Product Description

Product Description

The ASSY Flat Washer Head (FWH) is a multi-purpose engineered structural screw with a large washer head.  Code-approved reliability, the ASSY FWH has been awarded an ICC-ESR approval in the United States.

The head pull-in resistance is increased with the head of this screw. The use of an additional washer on the screw head is not required for many standard applications.



Diameter5/16″ (8 mm)
Lengths6-1/4″ (160 mm) to  15-3/4” (400 mm)
  • Provides tremendous head pull-through capacity
  • Offers a clean countersunk finish
  • Aggressive self-tapping tip bites into the wood and assures quick and easy installation
  • Partially threaded to pull members together tightly 
  • Equipped with a shank cutter to ease installation
  • Counter Thread Tip cuts the wood and pushes it aside
  • Suitable for ledger board to rim joist connections, and ledger board to stud wall connections
  • Ideal for Cross Laminated Timber (CLT) panel-to-panel connections
  • All ASSY fasteners can participate in LEED BD+C 2.0 certification [MRc 4.1 & 4.2, 2 points possible] thanks to the percentage of post-consumer recycled steel used to manufacture them. LEED certification letter is available on request.

The ASSY FWH is a two-in-one engineered screw that combines the pulling power of a washer-head screw with the clean finish of a countersunk head screw.  The FWH like the other ASSY screw is a structural, self-tapping screw with a counter thread tip for reduced wood splitting and precise setting.



SpecificationASSY F.W.H.Thread LengthAW Drive BitPackaging Qty.
# ItemMaterialHead
[3] FWH08100Hardened SteelFlat Washer Head5/16" x 4"8 x 1003 1/8"80AW 4050
[3] FWH08160Hardened SteelFlat Washer Head5/16" x 6 1/4"8 x 1603 1/8"80AW 4050
[3] FWH08200Hardened SteelFlat Washer Head5/16" x 7 7/8"8 x 2003 1/8"80AW 4050
[3] FWH08240Hardened SteelFlat Washer Head5/16" x 9 1/2"8 x 2404"100AW 4050
[3] FWH08300Hardened SteelFlat Washer Head5/16" x 11 7/8"8 x 3004"100AW 4050
[3] FWH08360Hardened SteelFlat Washer Head5/16" x 14 1/4"8 x 3604"100AW 4050
[3] FWH08400Hardened SteelFlat Washer Head5/16" x 15 3/4"8 x 4004"100AW 4050
CAD Drawings

CAD Drawings

ProductASSY FWH DiameterFile Extension
ASSY FWH5/16"8
Design Guides

Design Guides

Structural Screw Design Guide

The most complete tool for high-capacity mass timber connections design using ICC and CCMC code approved ASSY structural fasteners.

Structural Mass Timber Fastening Design Guide

Companion to the Structural Screws Design Guide, it provides pre-designed, easy-to-read tables for tens of mass timber connections using high-capacity ASSY self-tapping screws.

Code Approvals

Code Approvals

ICC Code Approval ESR-3179 for Partially Threaded Fasteners - 2021 Edition (August)

CCMC Code Approval 13677-R

ISO 50001 Certification for ASSY Fasteners

LA Research Report (LARR): RR 26073

Installation Instructions

Installation Instructions

Structural Fasteners Installation Guide

The structural fasteners installation guide is a practical document designed to simplify the installation process of ASSY self-tapping screws.

White Papers

White Papers

Timber Moisture Content Changes and Associated Stress Predictions on Structural Wood Screws

4D+ Embedment Reduction Factor for Screws Loaded in Withdrawal

Technical Blogs

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