It is challenging to securely attach items to concrete since concrete is rock-hard, prone to cracking, and difficult to drill into. But with just a small handful of the right tools and materials, it's possible to do so—efficiently and safely.
With concrete anchors, you can attach even heavy materials like deck ledger boards and framing members to concrete in just a few minutes.
What Are Concrete Anchors?
A concrete anchor is a steel fastener that is embedded in concrete to fix another item in place, allowing the concrete to carry the load.
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 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 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.
Compress into pre-drilled hole
3/8- to 1/2-inch diameter
Poor for use near edges because hole is expanded
Some are removable, some are not
Tap into pre-drilled hole
Light- to medium-duty
Up to 1/4-inch
Good for use near edges because they do not deform hole
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.
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.
How to Use Drop-in Concrete Anchors
Drill the Hole
Drill the hole. Clear out the hole with the shop vacuum.
Place the Sleeve in the Hole
Drop the female threaded sleeve into the hole, slit-end first.
Place the Set Tool
Place the narrow end of the set tool into the sleeve.
Strike the Anchor
Hammer the top of the set tool several times with the hammer until the sleeve is fully set in place.
Do not pound on the bolt itself as this may strip the threads. Use only the set tool.
Add the Bolt
Add the threaded bolt and washer to the sleeve. With a wrench, turn the bolt clockwise until it is firmly set in place.
How to Use Wedge Concrete Anchors
Drill the Hole
Drill a hole with the hammer drill and clear debris with the shop vacuum.
Place the Wedge Anchor
Fit the wedge end of the wedge anchor into the pre-drilled hole.
Strike the Wedge Anchor
Pound the wedge anchor into the hole with a hammer until the bottom of the threads are flush with the top of the concrete.
Add the Washer and Nut
Place a hole in the fixture to be attached over the anchor bolt and place the washer and nut on the threaded end of the wedge anchor.
Tighten the Nut
With an open-end wrench, turn the nut clockwise until it tightens against the washer. This expands the wedge, holding the anchor in place in the hole.
How to Use Sleeve Anchors
Drill the Hole
Drill a hole in the concrete with the hammer drill and clear the debris from the hole.
Add the Sleeve Anchor
First, push the sleeve anchor through a hole on the item to be attached to the concrete. Then continue the anchor into the pre-drilled hole in the concrete.
Strike the Anchor
Pound the top of the anchor with the hammer.
Turn the Nut
Place the washer and nut on the end of the exposed bolt and turn the nut clockwise. Firmly turn until it can no longer rotate. Turning expands the bottom of the anchor.
Anchor in Concrete. American Concrete Institute