Star makes construction lag screws that solve the pre-drilling problem. Their Con Lag line combines star drive heads with Type 17 cut points and 1,500-hour salt spray ratings — features that matter when you’re fastening ledger boards in Montana’s freeze-thaw climate.
Advanced Fastening for Structural Wood
Star Con Lag screws come in three key sizes: 5/16” x 4”, 5/16” x 3”, and 5/16” x 2-1/2”. All three share the same core technology that sets them apart from traditional lag bolts.
The star drive system changes everything. T30 bit size means no cam-out, no stripped heads, no swearing at your impact driver. The reinforced neck design handles the torque without snapping — something you’ll appreciate when driving through old-growth lumber or hitting a dense knot.
Type 17 cut point eliminates the need for pre-drilling in most wood types. That’s not marketing fluff. The aggressive serrated threads actually bite and pull themselves through the wood. Save your drill bits for pilot holes in steel.
| Specification | Value |
|---|---|
| Diameter | 5/16 inch |
| Lengths | 4”, 3”, 2-1/2” |
| Material | High-Corrosion-Resistant Carbon Steel |
| Coating | Bronze Ceramic (1,500 Hour Salt Spray Rating) |
| Drive Type | Star Drive (T30 Bit Size) |
| Head Style | Truss / Washer Head |
| Thread Design | Aggressive Serrated Threads with Type 17 Cut Point |
The truss head acts like a built-in washer, distributing load across a wider surface. No separate washer needed. Fewer parts to drop off the ladder.
Weather Resistance That Matters
1,500 hour salt spray rating for superior rust and corrosion protection puts these screws in a different league than zinc-plated alternatives. Bronze ceramic coating handles Montana’s moisture cycles — spring snowmelt, summer thunderstorms, winter freeze-thaw.
Suitable for use with ACQ, CA, and CCA treated lumber. That compatibility matters. Modern pressure-treated lumber eats through inferior coatings. These screws work equally well in cedar and redwood construction — the natural acids in those species won’t compromise the coating.
The coating exceeds standards. Exceeds 1,000-hour salt spray test (ASTM B117 standards) according to the 3-inch specs, while the 4-inch version claims even higher performance. Either way, you’re getting corrosion resistance that outlasts the lumber it’s holding.
Size Selection for Montana Projects
The three sizes cover most structural wood fastening:
5/16” x 4” - Fastening deck ledger boards and structural framing. This is your go-to for attaching ledgers to rim joists. The extra length handles 2x material plus sheathing with penetration to spare.
5/16” x 3” - Deck building (ledgers, posts, joists). Perfect for post-to-beam connections and joist hangers that need more than nails can provide. Approximately 30-40 pieces (standard 1lb box contains ~30 pcs) gives you enough for a typical deck post installation.
5/16” x 2-1/2” - Stair stringers and railing posts. Shorter length for connections where you don’t want to punch through the other side. Still plenty of holding power for critical safety connections.
All three sizes handle outdoor structural wood projects: decks, stairs, play sets, gazebos, and pergolas. The consistent 5/16” diameter means one drill bit for pilot holes when you do need them (metal brackets, near edges, or extra-hard species).
The Bottom Line
Star Con Lags deliver on their promises. The self-drilling feature actually works. The corrosion resistance holds up. The star drive doesn’t strip out.
Are they more expensive than basic lag bolts? Yes. Do they save enough time and frustration to justify the cost? On any job where labor matters more than materials, absolutely.
Skip them for temporary construction or interior work where corrosion doesn’t matter. But for permanent outdoor structures — deck ledgers, stair assemblies, pergola connections — these screws earn their keep. The combination of no pre-drilling, superior corrosion resistance, and cam-out-proof driving makes them the right choice when the connection has to last.
Frequently Asked Questions
Q: What size star drive bit do I need for Star Con Lag screws?
Star Con Lag screws use a T30 star drive bit for the 5/16” x 4” size, while the 5/16” x 3” size requires a T25 bit. The star drive system prevents cam-out and provides higher torque transmission compared to traditional hex heads.
Q: Can Star Con Lags be used with pressure-treated lumber?
Yes, Star Con Lag screws are specifically designed for ACQ, CA, and CCA treated lumber compatibility. The bronze ceramic coating with its 1,500-hour salt spray rating resists the corrosive chemicals in modern pressure-treated lumber.
Q: Do I need to pre-drill holes for Star Con Lag screws?
No, Star Con Lags feature a Type 17 cut point that eliminates pre-drilling in most wood types. The aggressive serrated threads and self-drilling point allow the screws to bite and pull themselves through the wood without pilot holes.
Q: What’s the actual corrosion resistance rating on these screws?
Star Con Lag screws feature bronze ceramic coating with ratings between 1,000 to 1,500 hours of salt spray testing (ASTM B117 standards). This epoxy-based coating significantly outperforms standard zinc plating for exterior applications.
Q: How many Star Con Lags come in a 1-pound box?
A 1-pound box of Star Con Lag 5/16” x 3” screws contains approximately 30-40 pieces, with 30 pieces being the standard count. The quantity varies slightly based on the specific length you choose.
Q: What size projects are these screws designed for?
Star Con Lag screws handle structural wood connections like deck ledger boards (5/16” x 4”), post-to-beam connections and joist hangers (5/16” x 3”), and stair stringers or railing posts (5/16” x 2-1/2”). All sizes work for decks, pergolas, play sets, and heavy-duty framing applications.
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