With concrete anchors, you can attach even heavy materials like deck ledger boards and framing members to concrete in just a few minutes.
Concrete Anchors vs. Concrete Screws
Concrete anchors and concrete screws both can be used to fasten items to concrete. Concrete anchors, generally speaking, expand in a pre-drilled hole, while concrete screws tap or cut threads in a pre-drilled hole.
Concrete Anchors
Concrete anchors fit into a pre-drilled hole and expand within the hole either by hitting the anchor with a hammer or by turning it with a wrench. Use concrete anchors for heavy items like framing members, deck ledger boards, signs, security cameras, and porch railings.
Concrete Screws
Concrete screws insert into pre-drilled holes in the concrete and self-tap the surrounding material as they are turned clockwise. Use concrete screws for lighter-weight items like hose reels, drainpipes, electrical boxes, conduit clamps, furring strips, and window and door framing.
Types of Concrete Anchors
Drop-in Concrete Anchors
Drop-in concrete anchors consist of two pieces: a male threaded bolt and a female threaded sleeve with a knurled end and slits. The slits allow the lower part of the anchor to expand. The sleeve is dropped in and then set solidly in place with a metal set tool. After the sleeve is in place, it cannot be removed from the concrete, though the male bolt can be removed from the sleeve.
Wedge Concrete Anchors
A wedge anchor is a male threaded bolt with a shielded wedge on the lower part that expands as a nut is turned against a washer on the bolt. The bolt and the shielded wedge are one piece, not two separate pieces as with the drop-in and sleeve anchors. Wedge concrete anchors are easy to insert, yet they hold very firmly in concrete. Once in place, wedge anchors cannot be removed, but the nut can be removed from the anchor.
Sleeve Concrete Anchors
A sleeve anchor consists of four pieces: a threaded bolt and a metal sleeve tube with large slots and narrow crosscuts, plus a nut and washer. The slots and crosscuts allow the sleeve to expand when it is tightened by the bolt. Furthermore, a smooth wedge at the bottom of the threaded bolt pulls upwards to force the bottom of the sleeve to expand.
Safety Considerations
Carefully study the concrete anchor’s product specifications before installation. Be aware of the concrete anchor’s weight limitations, both in terms of shear and pull-out strength. Do not over-torque concrete anchors. Use safety glasses when striking or turning concrete anchors.
