Buy Purlin Bolts Nuts Online in Australia
Purlin Bolt & Nut Quick Reference
Purlin bolts are hex flange fasteners connecting roof purlins, wall girts and secondary structural framing to primary steel frames. The flange head + flange nut distribute load over thin-section purlin, preventing pull-through (the failure mode for standard bolts in light-gauge sections). AIMS stocks Bremick and Hobson purlin bolts in multiple grades and finishes.
| Bolt Size | Common Lengths | Grade Standard | Best For |
|---|---|---|---|
| M10 | 20, 25, 30, 35, 40, 50 mm | Grade 4.6 ZP / Grade 8.8 HDG | Light-duty secondary connections — small purlins, lightweight cladding rails |
| M12 | 25, 30, 35, 40, 50, 65, 80 mm | Grade 4.6 ZP / Grade 8.8 HDG | Workshop default for standard purlin work |
| M16 | 30, 40, 50, 65, 80, 100 mm | Grade 4.6 ZP / Grade 8.8 HDG | Heavier purlins, structural connections, larger building frames |
| M20 | 50, 65, 80, 100 mm | Grade 8.8 HDG | Heavy industrial buildings, large mass framing |
Grade selection: 4.6 ZP for non-critical secondary connections. 8.8 HDG for outdoor + structural applications (galvanised for corrosion resistance). For matching nuts: hex flange nuts of same size + grade + finish. For Tek screws as an alternative on light-gauge purlins, see self-tapping screws with our guide. Companion: structural bolts, coach bolts, dynabolts.
Purlin Bolts & Nuts — Structural Fasteners for Steel Framing and Roof Purlins
Purlin bolts are specially designed hex flange fasteners used to connect roof purlins, wall girts and secondary structural steel framing to primary steel frames. The flange head and nut distribute load over the thin-section purlin, preventing pull-through — a failure mode that can occur with standard bolts in light-gauge sections. AIMS Industrial stocks purlin bolts and nuts from Bremick and Hobson in multiple grades and finishes.
Grades and Finishes
Grade 4.6 purlin bolts are the standard specification for secondary structural connections in non-critical steel framing. Zinc plated (ZP) Grade 4.6 is used in protected internal applications; hot-dip galvanised (HDG) Grade 4.6 is specified for external and coastal applications where corrosion resistance is required.
Grade 8.8 purlin bolts are high-tensile, providing greater clamping force for structural connections subject to higher loads — including wind uplift connections and primary frame connections in engineered steel buildings. Available in both zinc plated and hot-dip galvanised finishes.
Types
Hex flange bolt and nut kits include the purlin bolt and matching flange nut as a matched pair — reducing the risk of grade mismatch between bolt and nut. M12 bulk packs (200 piece and 150 piece) are available for volume installation work.
Shoulder purlin bolts have a stepped shoulder below the flange head — providing a bearing surface for shear load transfer at beam and column connections.
Standards and Specification
Purlin bolts should be specified in accordance with AS 4600 (Cold-Formed Steel Structures) and the building manufacturer's specification. The bolt grade, diameter, length and finish must match the engineer's design requirement. Do not substitute a lower grade or lighter finish than specified.
Need purlin bolts in bulk quantities or non-standard specifications? Contact our team.