What is the difference between a wedge anchor and a concrete screw?

A wedge anchor expands in the hole and leaves a threaded stud with a nut at the surface, while a concrete screw cuts threads into the concrete as it is driven. Wedge anchors are usually chosen for heavier-duty permanent connections in solid concrete, and they cannot be removed once set.

Can a wedge anchor be used in brick or block?

It is intended for solid concrete, not hollow block, brick with voids, or weak masonry. Using it in the wrong base material can lead to poor holding strength, cracking, or sudden failure under load. Sleeve anchors or masonry screws are better options for hollow or soft masonry.

Can I reuse a wedge anchor?

No. Once it has been installed and expanded in concrete, it is generally considered a one-time fastener. The expansion clip deforms during installation and cannot be reset. If the anchor is removed or disturbed, a new anchor should be installed in a new hole.

Why is my wedge anchor spinning in the hole?

The hole may be oversized, the concrete may be damaged or too weak to grip the expansion clip, or the anchor may not have enough embedment to engage properly. Simply tightening harder will not correct a bad hole or failing concrete. The anchor should be replaced in a new, correctly drilled hole.

Do I need a permit to install wedge anchors?

Not for minor nonstructural attachments by themselves, but anchors used for structural, life-safety, or permitted work are part of the approved installation. In those cases the anchor type, size, embedment, and placement often matter to inspection and must match the approved plans or engineering.

Wedge Anchor - Concrete Expansion Fastener Use Guide

A wedge anchor is an expansion-type concrete fastener that grips the sides of a drilled hole as a nut is tightened on the exposed threaded stud.

Wedge Anchor diagram — labeled parts, dimensions, and installation context

What It Is

A wedge anchor is made for solid concrete and develops holding power by expanding a clip at the embedded end of the anchor body. As the nut is tightened at the surface, the threaded stud pulls upward and forces a wedge-shaped clip outward against the concrete hole wall. This mechanical expansion creates a strong friction-based connection that resists both pullout and lateral loads.

Wedge anchors are widely used because they are simple to install, reliable in solid concrete, and available in common diameters from 1/4 inch through 1-1/4 inch, with lengths ranging from about 1-3/4 inches to 18 inches or more. Common materials include zinc-plated carbon steel for dry locations, galvanized steel for moderate moisture, and stainless steel for wet or corrosive environments.

Performance depends on correct hole diameter, embedment depth, torque, edge distance, and concrete strength. A hole that is even 1/16 inch oversize can dramatically reduce holding capacity because the clip cannot expand enough to grip firmly.

Types

Standard wedge anchors are the most common form, consisting of a threaded stud body, an expansion clip at the bottom, a nut, and a washer. They are installed by dropping the anchor into a pre-drilled hole, setting it to the correct depth, and torquing the nut to expand the clip.

Fully threaded wedge anchors have threads running the full length of the stud rather than just the top portion. This allows more flexibility in setting the projection height above the concrete surface.

Some manufacturers offer seismic-rated wedge anchors that are tested and listed for use in cracked concrete and seismic zones. These anchors have modified clip designs and are evaluated under ICC-ES criteria for use in structural applications where earthquake loads must be considered.

Where It Is Used

Wedge anchors are used to fasten sill plates, railings, post bases, equipment brackets, machinery pads, structural steel column bases, and mechanical or electrical hardware to concrete slabs, foundations, and walls. They are used in both residential and commercial work where a permanent concrete connection is needed.

In residential construction, common applications include anchoring mudsills to foundation walls, securing handrail posts to concrete stoops, and mounting garage door track brackets to concrete floors. In commercial and industrial settings, wedge anchors fasten equipment pads, steel base plates, and safety bollards to concrete floors and footings.

Wedge anchors are not suitable for hollow-core block, brick with voids, or cracked concrete unless specifically listed for those conditions. Using a wedge anchor in the wrong base material can result in splitting, pullout, or failure under load.

How to Identify One

A wedge anchor is visible as a threaded stud projecting from concrete with a nut and washer at the surface. The stud diameter matches common bolt sizes and the projection height depends on the application. Unlike a concrete screw, which has a hex head and cuts threads directly into the concrete, a wedge anchor stays in the concrete permanently once installed and cannot be driven deeper or backed out without destroying the connection.

If you remove the nut and washer, the threaded rod does not come out of the hole because the expansion clip at the bottom is locked against the concrete. This permanence distinguishes it from removable fasteners like sleeve anchors or concrete screws.

Replacement

Replacement is needed when the anchor corrodes, loosens, is damaged during removal of the attached fixture, or no longer meets the load requirement for the attached item. Because a wedge anchor cannot be pulled out of the hole once set, replacement means cutting the stud flush with the surface or below, drilling a new hole at the required edge and spacing distances, and installing a new anchor.

Failed wedge anchors should be evaluated with the concrete condition and spacing in mind, not treated as a simple hardware swap. If multiple anchors in a pattern are failing, the cause may be undersized anchors, inadequate embedment, or deteriorated concrete rather than a single defective fastener.