Timber Bolts
What are timber bolts?
Timber bolts are round-head structural bolts made for fastening heavy wood members. Under the head they typically include anti-rotation lugs/nibs (or a small bearing ring) that bite into the timber so the bolt won’t spin while you tighten the nut. The smooth, low-snag head protects surfaces and hardware in public-facing installs.
Why choose timber bolts
- One-side installation — under-head lugs lock into the wood so you can tighten from the nut side only.
- Smooth, robust head — rounded profile resists snagging and looks clean on exposed structures.
- Built for wood structures — long shank lengths and washer/nut compatibility for high clamp loads.
- Outdoor-ready options — hot-dip galvanized and stainless selections for weather exposure.
Materials & finishes for timber bolts
- Carbon steel for general structural use.
- Hot-dip galvanized steel for thick, durable corrosion protection in exterior work.
- Stainless steel (304 / 18-8) for broad corrosion resistance; 316 for coastal/chloride environments.
- Pair with matching nuts and washers (same material/finish) to maintain corrosion compatibility.
Common applications for timber bolts
- Timber framing, pergolas, pavilions, boardwalks, and bridges
- Utility and site structures, outdoor furniture, and guardrails
- Post-and-beam connections and heavy landscaping timbers
- Playgrounds and public installations where a smooth head is preferred
How to size and specify timber bolts
Order by diameter × thread × length (e.g., 1/2″-13 × 8″). Length is measured from under the head to the end of the bolt. Choose the material/finish for the environment and pair with appropriate flat washers, lock washers, and nuts to meet design loads.
Installation tips for timber bolts
- Drill a snug, straight hole; tap the head to seat the lugs before final torque.
- Use large-OD flat washers to distribute load and protect wood fibers.
- Where vibration is expected, add lock washers or a prevailing-torque/locknut.
- For exterior assemblies, keep materials matched (e.g., galvanized bolt + galvanized hardware).
Timber Bolts FAQs
See the accordion below for quick answers on sizing, materials, and best practices for long-lasting structural connections with timber bolts.
Both have round heads, but timber bolts include under-head lugs/ring that bite into wood for anti-rotation in large structural members.
From under the head to the end of the bolt (not including the head).
Hot-dip galvanized is a durable, economical exterior finish; stainless offers broader corrosion resistance, with 316 preferred near salt or chlorides.
Yes. Use large-OD flat washers to spread load; add a lock washer or locknut where vibration or cyclic loads are present.
Pre-seat the lugs by drawing the bolt snug, or lightly relieve the surface to help the lugs bite. If necessary, use a clamp to hold the head while seating.
Yes, use washers against the metal and ensure the lugs can still bite the wood side so the head doesn’t rotate.
Match thread and material/finish (galvanized with galvanized, stainless with stainless). Structural connections often use heavy-hex or locknuts per design.
Replace if threads are stretched, the shank is bent, the head lugs are rounded and won’t engage, or if corrosion loss is evident on exterior hardware.