#14 × 3" Structural Wood Lag Screws - Heavy Duty Fasteners
Product Introduction
The Fasto #14 × 3-inch structural wood lag screw is a code-grade replacement for traditional hex-head lag bolts in deck ledger connections, timber frame joinery, and heavy exterior wood construction. Manufactured from heat-treated carbon steel at our IATF 16949-certified facility, each screw combines a T30 star drive for zero-cam-out driving, a modified truss washer head for superior clamping distribution, and a Type 17 self-tapping point that eliminates pre-drilling in softwoods. The proprietary 4-layer black coating system has been independently validated to 1,000 hours of ASTM B117 salt spray resistance — making it safe for direct contact with ACQ pressure-treated lumber and outdoor exposure in all climate zones. Supplied in a 54-piece contractor pack, these screws are the fastener of choice for professional deck builders, timber framers, and log home contractors across North America.
Technical Specifications
| Technical Specifications | Value | Standard |
| Nominal Diameter | #14 (0.242 in / 6.15mm) | ANSI/ASME B18.6.1 |
| Overall Length | 3 in (76.2mm) | DIN 571 |
| Head Diameter | 0.625 in (15.9mm) | |
| Head Style | Modified Truss Washer Head | |
| Drive Recess | T30 Star Drive (6-Lobe Torx) | ISO 10664 |
| Thread Type | Deep-Cut Coarse Thread | |
| Thread Length | 2.36 in (60mm) | |
| Point Type | Type 17 Notched Self-Tapping | |
| Shank Feature | Knurled (Torque-Reducing) | |
| Material Grade | Heat-Treated Carbon Steel (Alloy) | |
| Surface Finish | 4-Layer Black Coating | |
| Corrosion Resistance | 1,000-Hour Salt Spray (ASTM B117) | ASTM B117 |
| ACQ Compatibility | Yes — ACQ-C / ACQ-D Treated Lumber | AWPA U1 |
| Pilot Hole — Softwood | 3/16 in (4.8mm) | |
| Pilot Hole — Hardwood | 7/32 in (5.5mm) | |
| T30 Bit Included | Yes (1 pc per pack) | |
| Pack Quantity | 54 Pieces | |
| Certifications | IATF 16949, ISO 9001, CE, SGS, ROHS |
Engineering Breakdown
T30 Star Drive Head
The 6-lobe T30 Torx recess delivers direct, slip-free torque transfer. Unlike Phillips drives — which are intentionally designed to cam-out at high torque — the T30 star geometry holds the driver bit securely even under maximum load. The deep engagement pocket enables one-handed driving from ladders or scaffolding. The modified truss washer profile sits flush with the wood surface and provides 22% more bearing area than a standard flat head, distributing clamping force evenly without crushing softwood fibers.
Knurled Shank & Deep Thread
The knurled shank is a precision-engineered torque-reduction feature. As the screw advances, the knurled collar reams the pilot hole to a clearance diameter, eliminating the friction lock that causes 90% of screw snapping failures in hardwoods. The deep-cut coarse thread profile maximizes wood fiber engagement — each thread flight captures more material than standard deck screw threads, producing up to 350 lbs of withdrawal resistance per screw in SPF lumber.
Type 17 Notched Point
The Type 17 auger-style notched point cuts a clean entry path through wood fibers at the tip, rather than wedging them apart as a standard sharp point does. This eliminates the splitting risk in hardwoods and near board edges, and can eliminate the need for a pilot hole entirely in softwoods (pine, cedar, spruce). The precise notch geometry is CNC-ground for batch-to-batch consistency, ensuring the same self-tapping performance from the first screw to the last in every pack.
Application
Manufacturing Facility
Certifications
Quality Control
Why Fasto？
20+ Years of Export Expertise
Serving global B2B fastener buyers since 2005. Deep understanding of international standards (DIN, ISO, ANSI, ASME) and regional market requirements across North America, Europe, and Asia-Pacific.
IATF 16949 Certified Factory
Automotive-grade quality management in every batch. Full material traceability from raw steel coil to finished fastener. Third-party audited annually by SGS and TÜV.
80k+ sqm Manufacturing Campus
In-house cold heading, thread rolling, heat treatment, and coating lines. No outsourced steps. Full control over lead times, quality, and cost from a single integrated facility.
OEM & Custom Engineering
Custom head markings, packaging, and dimensional modifications available. Our engineering team can develop application-specific fasteners with full PPAP documentation for volume programs.
FAQ
What size pilot hole should I drill for #14 structural lag screws?
Drill a 3/16" (4.8mm) pilot hole in softwoods (pine, cedar, spruce, fir) and a 7/32" (5.5mm) pilot hole in hardwoods (oak, maple, ipe, mahogany). The pilot hole should extend to the full embedment depth. Fasto's knurled shank reams the hole during driving, reducing friction, but pre-drilling remains essential in dense species to prevent screw snapping.
Are structural screws a code-approved replacement for lag bolts?
Yes. Structural wood screws are accepted under the International Residential Code (IRC) as alternatives to traditional lag bolts for deck ledger attachments, beam-to-post connections, and other structural wood-to-wood fastening applications. Fasto #14 screws are manufactured from heat-treated alloy steel with shear and withdrawal capacities that match or exceed equivalent-diameter lag bolts.
Are these screws safe for ACQ pressure-treated lumber?
Yes. Fasto #14 structural lag screws are explicitly rated for direct contact with ACQ-C and ACQ-D pressure-treated wood. The 4-layer black coating system is engineered to resist the alkaline copper quaternary compounds in modern treated lumber. The coating is validated to 1,000 hours of salt spray exposure per ASTM B117.
What is the difference between a lag screw and a structural screw?
Lag screws (or lag bolts) traditionally refer to heavy hex-head wood screws requiring a socket wrench and separate washer. Structural screws are an engineered category of high-strength, code-listed fasteners designed as direct replacements. Fasto structural screws feature an integrated washer head, star drive, knurled shank, and Type 17 point that traditional lag bolts lack.
Why do my lag screws snap during installation?
Three most common causes: (1) Undersized pilot hole — friction heat builds and the shank shears. (2) Impact driver torque overload — high-torque drivers can exceed the screw's torsional capacity in dense hardwood. (3) No lubrication — applying bar soap or beeswax to threads dramatically reduces driving friction. Fasto's knurled shank mitigates this by reaming the hole during advance, reducing torque by ~30%.
How long will the black coating last outdoors?
With the 4-layer coating system, expect 10 to 15+ years of service life in typical outdoor applications away from direct saltwater exposure. Coating longevity is influenced by UV exposure, moisture cycling, wood treatment chemicals, and mechanical abrasion. For coastal installations (within 3 miles of saltwater), 316 marine-grade stainless steel is recommended.
Can I use an impact driver with these screws?
Yes, but with caution. An impact driver is suitable for driving in softwoods without a pilot hole. In hardwoods or when using a pilot hole, switch to a drill/driver with an adjustable clutch for final seating to avoid over-torquing and potential head or shank failure. The included T30 bit fits standard 1/4" hex impact driver chucks.
What certifications and standards apply?
Manufactured in an IATF 16949 and ISO 9001:2015 certified facility. Product certifications: CE, SGS, ROHS. Dimensional specs: ANSI/ASME B18.6.1 and DIN 571 (adapted for star drive). Corrosion testing: ASTM B117. Full material certificates and batch inspection reports available upon request.
Do you offer custom sizes or OEM packaging?
Yes. Fasto provides full OEM/ODM services including custom lengths, diameters, head markings, coating colors, and retail-ready packaging (blister cards, plastic boxes, bulk pails). Available sizes: #14x3", 4", 5", 6", 8", 10", 12" and 5/16" heavy-duty variants. Contact sales with your specifications for a quotation.
How do I prevent structural screws from loosening over time?
Use the correct pilot hole diameter for the wood species to ensure full thread engagement. Fasto's deep thread profile maximizes wood fiber contact for long-term holding power. Avoid over-torquing during installation, as this can strip wood threads and reduce withdrawal resistance. For critical connections, follow IRC-specified spacing and edge-distance requirements.