Structural Washers

Structural washers are hardened flat washers made to ASTM F436, used under the bolt head or nut in high-strength structural steel connections. Their hardness prevents the washer from being crushed or embedded under the high preload of A325 and A490 bolts, ensuring proper clamp load. We stock F436 structural washers plain and galvanized.

Why Hardened Washers

Standard flat washers would deform or brinell under the extreme tension of a structural bolt, losing preload and damaging the joint. ASTM F436 washers are through-hardened to resist this, maintaining a flat, solid bearing surface that transfers the bolt's full clamp load to the connected steel. They're required, not optional, in properly designed structural joints.

When They're Required

F436 washers are used under the turned element (the part being rotated during tightening) in structural connections, and over oversized or slotted holes to span the opening. Many structural specs require a hardened washer under both the head and nut. Follow the connection design and bolting spec.

Types

Circular: the standard round F436 washer. Beveled (square): for sloped flanges (like on certain steel beams) where a flat washer wouldn't bear evenly. Choose beveled where the bearing surface is sloped.

Finishes

Plain for protected interior structural use, hot-dip galvanized to match galvanized structural bolts in exterior exposure.

Selecting the Right Structural Washer

Match the washer to the structural bolt diameter and use F436 hardened — never a standard washer — under high-strength bolts. Choose galvanized to match galvanized bolts, beveled for sloped surfaces. Place per the connection design (under the turned element and over oversized holes). Confirm the spec's washer requirements for your joint.

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