With the right tools and hardware, mounting to concrete is easy
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Many people struggle with fastening to concrete–and other masonry surfaces, such as brick and concrete block. Turns out, there’s nothing to it. The best way to fasten to it, especially for DIYers, is to just dill a hole and drive a screw.
The job’s bad reputation was well earned but is out of date. Years ago, fastening to concrete was difficult and hit or miss. If you’ve ever tried driving hardened-steel nails into concrete or tried to make anchor sleeve holes with a wobbly rental masonry drill and a dull rental drill bit than you know about frustration.
The thing that changed all that is the ordinary cordless drill. More specifically, the cordless drill with a hammer function.
This tool makes short work of punching a reliable hole in concrete, mortar, brick, Portland cement plaster (stucco), and even many types of stone. Once you have that hole–properly known as a pilot hole– you can drive a masonry screw or bolt into it, or you can install a soft sleeve into which you can drive a wood screw or sheet metal screw. It’s that easy.
Since you start with a drill and bit, that’s where we’ll begin this discussion.
Many cordless drills today are equipped with a hammer function. I’ve talked to people who didn’t even know this was included on their drill. Compared to a cordless drill without this feature, it’s a slight upcharge–about $20, on average. A hammer function provides a percussive action to chip away and pulverize masonry as a masonry bit spins. To help these specialized drill bits withstand such harsh use, they have a piece of carbide brazed to their tip. Carbide is not a single material, but a mixture of them. It starts out as carbide powder intermixed with a metal powder, such as tungsten. The powders are mixed with a binder additive, formed into a shape, machined, and then fused together at high temperature forming a composite. The carbide tip is brazed onto the body of the drill bit producing a device that is both flexible and wear resistant, yet has an extremely hard tip. Drill a hole with that bit, then drive a hardened masonry screw into it.
A masonry drill bit has a tip made out of tungsten carbide, brazed onto the body of the drill. The bit is capable of withstanding the high impact and wear created by drilling into concrete and masonry. A high-strength masonry screw can be driven directly into this hole. Another fastening option (shown below) is to insert a plastic or metal sleeve into the hole and drive a screw into the sleeve.
Turn the selector ring on the cordless drill, aligning the hammer icon with the white selector triangle. Move the drill’s speed selector switch to its top speed, 2 or 3, depending on the drill. Tighten the drill’s chuck on the masonry bit.
With the carbide drill bit chucked in the drill, hold what you need to fasten to the wall and make your hole. For brackets and the similar pieces of hardware, use their mounting holes to place the drill bit. For wood, simply bore right through the wood and into the concrete.
When the hole is established, you can move the hardware or lumber out of the way and continue boring to the hole’s full depth. When drilling mounting holes in long pieces of wood or metal, drill one mounting hole, then drive a screw at that point. Level the workpiece, drill a second hole, and drive a second mounting screw. With the workpiece fastened at two points, and level, drill remaining mounting holes and drive the remaining screws.
The fastest way to drive a masonry screw is with the same drill driver that made the hole. Turn the drill’s selector to the drive setting, turn the clutch to the maximum number, and use a nut driver or drive bit to sock down the screw.
Amateurs and professionals alike often forget that safety and drilling a high-quality hole go hand-in-hand when fastening to concrete.
Wear your safety glasses during every step of the process. Concrete chips can fly, a masonry screw may inadvertently break, you might even snap the drill bit itself if it gets bound up against a piece of reinforcing steel. All of this can cause debris to go flying.
Next, wear a dust mask. Pulverizing conctete with a drill bit creates dust, and some of that dust becomes airborne while drilling and, later, when you clean out the hole.
And that brings us to a few other points that are frequently overlooked:
It may be simple and generally safe to fasten to concrete, but it’s always a good idea to wear safety glasses, if nothing else to shield yourself from the dust that’s produced in the process.
A simple dust mask works well enough to protect you from airborne cement dust created when you drill into concrete and when you remove it.
Tapcon’s massive concrete screw can be used for heavy-duty applications, such as fastening posts to a concrete slab.
Some heavy-duty plastic anchors, such as the Red Head Polyset, can be driven into a hole in concrete. From there, you use the included pan head sheet metal screw to fasten whatever you need.
Lag shields are hollow soft metal sleeves that are driven into a hole. When a screw or bolt is driven into the cavity in the center of the sleeve, the fastener’s threads cut into its wall, which is softer than the steel screw or bolt.
Sleeve anchors are hybrid fasteners consisting of a threaded stud, a nut, and a specialized sleeve. You hammer this fastener into the hole then turn the nut no more turns than specified by the manufacturer (typically two to four). This causes the threaded stud to pull up in the sleeve. As it does so, the the sleeve expands against the wall of the hole, forming a tight wedging action. It’s important to read the manufacturer’s instructions before installing these. They are to be located specified distances from each other and from the edge of the slab.
Hammer set anchors are simple fasteners that fit through a hole in whatever you are fatsening, such as a shelf cleat, bracket or other piece of hardware. Their dome-shaped head bears down on the surface of the workpiece. Slip the fasteners through the wokrpiece, into the hole in the concrete and then drive the nail in them until it is fully seated against the dome-shaped head. These fasteners work best when used in applications where one is enough to attach the load. Using more than one on at a time requires careful drilling to ensure that the fasteners line up both with the holes in the mounted object and in the concrete.
You can make your own concrete fastener for horizontal applications by using a small bolt or piece of threaded rod embedded in mortar, epoxy repair mortar, or the specialized epoxies used for embedding rebar. Drill a hole twice the diameter of the threaded rod or bolt. You can either place the fastener in the hole and then push the filling material in around it or with thinner materials, fill the hole to the halfway point and then push in the fastener. Be sure to turn the fastener back and forth to ensure that it is locked into the embedding material. Also, use a square from two directions to check that the fastener is square or plumb to the surface.
Roy Berendsohn has worked for more than 25 years at Popular Mechanics, where he has written on carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care, chainsaw use, and outdoor power equipment. When he’s not working on his own house, he volunteers with Sovereign Grace Church doing home repair for families in rural, suburban and urban locations throughout central and southern New Jersey.
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