Structural Washers

Structural Washers for Australian Steel Construction

Structural washers are the third component of structural bolt assemblies — providing the bearing surface that distributes bolt load across the structural plate, prevents galling, and (in load-indicating versions) verifies correct bolt tension. For Australian structural steelwork compliant with AS/NZS 1252, structural washers are essential alongside the matched bolts and nuts. AIMS Industrial supplies structural washers from Hobson and approved fastener brands.

The structural washer types we stock

• Standard structural flat washers — hardened high-tensile flat washers in metric sizes M12 to M36
• Square structural washers — for connections where square footprint is required
• Load-indicating washers (DTI / Coronet washers) — washers with calibrated bumps that compress to indicate correct bolt tension
• Galvanised structural washers — hot-dip galvanised for outdoor and corrosive environments
• Self-colour structural washers — untreated for indoor applications

Why structural washers differ from standard washers

Structural washers are dimensionally and materially different from general-purpose washers in three ways:

• Hardened material — hardened steel that doesn't deform under high bolt tension
• Greater thickness — typically 4-8mm depending on size, much thicker than standard flat washers
• Tighter tolerance — dimensional consistency for engineered structural performance

Standard flat washers can deform under structural bolt tension, causing loss of preload and unreliable connection behaviour. Substituting standard washers for structural washers defeats the engineered performance of the assembly.

Load-indicating washers — verification of correct tension

Direct Tension Indicator (DTI) washers — also called Coronet washers — have raised bumps on one face that compress as the bolt is tightened. The gap between the washer and the bearing surface decreases predictably as bolt tension increases. When the gap reaches a specified width (typically 0.4mm for fully tensioned bolts), the bolt has reached the engineered tension. A feeler gauge verifies the gap; if the gap won't accept the gauge anywhere around the washer, tension is correct. DTI washers are increasingly specified for critical structural connections where torque or turn-of-nut methods are insufficient verification.

Where structural washers earn their place

• Steel building construction — under structural bolt heads and nuts in primary connections
• Bridge construction — high-tension connections in steel bridges
• Industrial heavy steelwork — load-bearing connections in industrial frames
• Pre-engineered buildings — moment-frame and rigid-frame connections
• Critical inspection-verified connections — DTI washers where bolt tension verification is required

Compliance — AS/NZS 1252

Structural washers used in Australian structural steelwork must comply with AS/NZS 1252. The standard specifies dimensions, hardness, materials, and marking requirements. Compliant washers carry the standard marking and grade identification visible on the washer face. Building inspectors verify compliance via these markings; unmarked or substandard washers can't be used in approved structural connections.

Sizing

Structural washers are sized to match the corresponding bolt diameter — M12 through M36 metric sizes are stocked. Each washer has specific outer diameter, inner diameter, and thickness specifications matched to the AS/NZS 1252 requirements. Don't substitute washer sizes; structural washers are paired one-for-one with the matching bolts.

Brands stocked at AIMS

Hobson covers the structural washer range across galvanised and self-colour finishes. Bremick stocks complementary structural washers. For load-indicating washers and specialty applications, sourcing through our distribution channels covers most requirements.

Surface treatment matching

Match the washer finish to the bolt and nut finish: galvanised bolts and nuts with galvanised washers, self-colour throughout for indoor applications. Mixed finishes cause galvanic corrosion in outdoor exposure.

Companion ranges at AIMS

Structural washers sit alongside our broader structural fastener range — see structural bolt assemblies, structural hex nuts, safety washers, and mudguard washers for the related products.

Need help speccing structural washers for a specific project, including DTI washers? contact our team — we'll match by size, type, and AS/NZS 1252 compliance.