How to find the right Lag Screws AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Lag Screws
- Lead hole size
- Drill the threaded portion's lead hole at about 40–70% of shank diameter in softwoods and larger in dense hardwoods, plus a full-shank-diameter clearance hole for the unthreaded section. This follows the long-standing NDS wood-design guidance; without a proper lead hole, lags split wood or twist off.
- Coating for treated lumber
- Use hot-dip galvanized or stainless lags with preservative-treated lumber. Copper-based preservatives corrode zinc-plated steel quickly.
- Washer
- Always fit a flat washer under the head when bearing on wood. The washer prevents the head from crushing into the wood fibers.
- Thread penetration
- The threaded length should be fully embedded in the main member, not in the piece being attached. Withdrawal capacity comes only from the threads in the receiving member.
Brands that matter
- Hillman: Retail lag screw assortments.
- Simpson Strong-Tie: Strong-Drive structural screws as lag replacements.
- FastenMaster: LedgerLOK and TimberLOK lag alternatives.
- GRK: RSS structural screws as lag replacements.
What to avoid
- Driving lags without a lead hole into hardwood or dense treated lumber.
- Zinc-plated lags in treated or exterior lumber.
Questions
Can a structural screw replace a lag?
Often yes, and it usually needs no pilot hole, but use only screws with a code evaluation report for that connection, such as a deck ledger.