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A wedge anchor is a type of specialty fastener used to attach objects to concrete or masonry structures. They may be used to secure a piece of artwork to a brick wall, hang ductwork or plumbing pipes from a ceiling, or bolt an item into the floor. Wedge anchors may also be known as anchor bolts or expansion bolts in some areas.
The standard wedge anchor consists of two components that are joined together by the manufacturer. A standard metal bolt makes up the base of the wedge anchor, and is surrounded by a metal or thermoplastic sleeve. Once an installer inserts the bolt into a masonry wall or floor, the base of the anchor slides up inside the sleeve. A rounded or conical tip on the end of the base forces the walls of the sleeve out to the side, where they grip the interior of the concrete or stone wall to form a secure hold.
Installers must select each wedge anchor carefully based on a number of factors. They must consider the load the anchor will need to support, as well as the composition and condition of the surface where it will be installed. Crumbling concrete and older walls, for example, require a more heavy-duty wedge anchor than new walls. Everything from the length, thickness, and material of the anchor bolt can impact the security of the installation. While standard steel works in most applications, galvanized or stainless steel may be required in areas subject to frequent moisture or chemical exposure.
Before installing a wedge anchor, contractors must drill a hole that's slightly longer than the anchor itself. This requires a hammer drill or other tool designed for drilling masonry. The stone or concrete surface must be completely clean and free of debris prior to installation. This includes removing any loose concrete and vacuuming or blowing away dust.
Next, the entire unit must be inserted into the pre-drilled hole and pounded in place using a hammer or mallet. Once the face of the wedge anchor sits flush with the surrounding surface, installers use a drill or screwdriver to turn the base of the anchor. As the base turns and draws up inside the sleeve, the walls of the sleeve wedge themselves against the walls of the hole. Heavy-duty applications require installers to use a torque wrench to ensure that the anchor has been installed correctly, and that sufficient force has been applied to ensure the finished project will be safe.