A sleeve anchor is a type of fastener used to secure objects to a concrete or masonry structure. They can be used to join two or more concrete structures, or to fasten an object such as a shelf to a brick wall. Sleeve anchors are also referred to as two-step bolts or anchor bolts in some areas.
The sleeve anchor consists of a solid metal screw or stud with a cone-shaped tip that flares out to the sides. A metal sleeve wraps around the outside of the stud, allowing the tip of the stud to extend out the end of the sleeve. A washer and nut sit at the top of the bolt for adjustment and installation. Once the sleeve anchor has been inserted into concrete, installers turn the nut to pull the stud up into the sleeve. As the flared end of the stud passes into the sleeve, it causes the sleeve to expand outward and grasp the concrete for a secure hold.
Sleeve anchor installation consists of a two-step process. First, the installer must drill a hole in the concrete using a hammer drill. The hole should be the same diameter as the bolt, but is often slightly longer than the bolt to allow for proper installation. The installer then uses a wire brush and vacuum to remove all concrete or masonry debris from the hole to ensure the bolt will fit properly. Any debris left in the hole could compromise the ability of the sleeve anchor to grasp the concrete or brick.
The installer then places the anchor into the hole and tightens it using a wrench. Depending on the manufacturer, the anchor bolt may require a specified number or turns to ensure it has been fully expanded. On some heavy-duty applications, manufacturers recommend using a torque wrench to apply a specified amount of force during installation.
Anchor bolts must be selected carefully based on the condition of the concrete and the weight of the object. Old or damaged concrete or brick requires heavier or longer sleeve anchors than a new, well-built concrete structure. The heavier the object is that's being fastened, the longer and thicker the anchor bolt will have to be to offer adequate support. Installers must also account for vibration or external forces that may be applied to the bolt. When anchor bolts are used outdoors or near corrosive chemicals, they should be galvanized to prevent rust or corrosion.