Wedge anchors (also known as through-bolts) are heavy-duty, torque-controlled expansion fasteners designed strictly for anchoring structural fixtures into solid concrete.
A wedge anchor is a male bolt with external threads at the top and a specialized expansion clip at the bottom.
They provide some of the highest hold capacities of any mechanical concrete fastener, making them the standard choice for structural steel columns, heavy machinery, ledger boards, and highway railings.
Core Mechanics
A wedge anchor features a slightly tapered, cone-shaped bottom enveloped by a small, free-spinning expansion clip.
- The Anchor Action: As you tighten the top hex nut with a wrench, the threaded bolt body is drawn upward.
- The Wedge Action: The stationary expansion clip is held in place by friction against the concrete wall. The upward movement forces the widening bottom cone directly into the clip, expanding it outward and wedging it tightly into the concrete.
Crucial Applications & Constraints
- Solid Concrete Only: Like drop-in fasteners, wedge anchors rely on the immense compressive strength of solid, cured concrete. They cannot be safely used in brick, lightweight cinder blocks, or mortar joints.
- Permanent Placement: Once expanded, the bottom clip permanently deforms against the concrete. You cannot pull a wedge anchor back out cleanly. If a fixture must be removed permanently, the protruding stud must be cut off flush with an angle grinder.
Material Variants: Use zinc-plated carbon steel for indoor dry storage areas. For outdoor, coastal, or chemical environments, opt for 304 or 316 Stainless Steel to prevent rust degradation.
