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Drilling a clean hole in concrete is mostly a matter of using the right bit, matching it to the plug, and keeping the drill straight. A standard twist bit and a cordless drill may work on soft masonry, but dense concrete can quickly overheat the bit, stall the tool, or leave a hole too wide for the plug to grip.
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Match the bit to the plug
Check the plastic plug’s packaging for its required hole diameter and depth. A common 6 mm plug needs a 6 mm masonry bit; an 8 mm plug needs an 8 mm bit. Do not size the hole by guessing from the screw diameter. The plug expands when the screw is driven, so its outside diameter—not the screw’s—is what matters.
Hole depth should be slightly greater than the plug length, usually by about 5–10 mm. That gives concrete dust somewhere to go and keeps the plug from bottoming out. If the screw passes through a bracket or other fixture, account for that thickness too: the screw must enter the plug far enough to expand it properly.
Choose a drill and bit for the wall
For a few small holes in ordinary brick or softer masonry, a corded or cordless drill with a hammer function can be enough. For concrete—especially dense or reinforced concrete—a hammer drill is a better choice. Its hammer action combines rotation with short blows, helping a carbide masonry bit break material instead of only rubbing against it. A regular drill has rotation only and can make very slow progress.
For occasional household jobs, a cordless hammer drill is a practical option. Use a carbide-tipped masonry bit sized to the plug. A rotary hammer with an SDS-Plus bit is faster and easier in hard concrete or when drilling many holes, but it costs more and is unnecessary for two small fixings. An impact driver is not the right tool for drilling these holes: its impacts are rotational, not the forward hammer action a masonry bit needs.
| Tool | Best for | Trade-off |
|---|---|---|
| Regular drill | Soft masonry and very occasional shallow holes | Slow in concrete; may overheat or stop cutting |
| Hammer drill | Most small plastic-plug holes in concrete | Needs a suitable masonry bit; can still struggle in very hard concrete |
| Rotary hammer | Hard concrete, larger holes, or repeated drilling | More expensive and often excessive for a small home repair |
Check the location before drilling
Look for electrical outlets, switches, plumbing fixtures, and pipes on both sides of the wall. Avoid drilling directly above or below a socket or switch, where cables may run, and use an appropriate cable or pipe detector if the route is uncertain. A detector reduces risk but cannot guarantee a safe drilling point. If you suspect the spot contains a cable or pipe, choose another location or get qualified help.
Wear safety glasses: concrete dust and small chips can fly out of the hole. If drilling overhead, wear a dust mask as well. Keep the work area clear, and support a ladder securely if you need one.
Mark, drill, and keep the hole straight
Mark the centre of the hole and check that the mark is not over a joint or a visibly cracked area. Measure the plug length and set a depth stop if the drill has one. Otherwise, wrap a strip of tape around the bit at the intended depth. Tape is a visual guide, not a physical stop, so keep watching it as you drill.
Fit the masonry bit firmly in the chuck and check that it runs straight. Start at a low speed with the bit held perpendicular to the wall. Once it has formed a shallow starting point, use steady pressure and the hammer setting. Let the bit cut; forcing it hard can make the drill overheat, bend the bit, or wander off the mark. Pull the bit out every few seconds to clear dust, especially in a deep hole.
If the drill suddenly stops advancing, do not keep squeezing the trigger. The bit may be packed with dust, the concrete may be particularly hard, or you may have hit reinforcing steel. Withdraw the bit, clear the hole, and try again with controlled pressure. If you hit metal, stop rather than trying to punch through it; shift the fixing location if possible. A standard plastic wall plug is generally not a suitable anchor where the hole intersects rebar.
Clean the hole and fit the plug
Remove the bit and clear loose dust from the hole with a hand pump, vacuum, or a small brush. Dust left at the bottom can stop the plug going fully in and reduce its grip. Avoid blowing concrete dust toward your face. Test the plug: it should enter the hole with firm tapping, not fall in loosely. If it pushes in without resistance, the hole may be oversized or the plug may be the wrong size. Use a larger suitable plug or make a new hole; do not rely on packing the gap with debris.
Tap the plug in until its rim sits flush with the wall. Drive the screw into the plug, stopping when the fixture is secure. Overtightening can strip the plug or spin it in the hole. For heavy loads, ceiling fixings, or anything where failure could cause injury, use an anchor rated for the substrate and load rather than assuming a basic plastic plug is enough.
Common mistakes and quick fixes
A hole that is too wide often comes from a worn bit, a bit that wobbles in the chuck, or drilling without a steady start. Replace badly worn bits and check the chuck before continuing. A plug that will not go in may mean the hole is too shallow or still full of dust; check the depth and clean it before hammering harder. If drilling is unusually slow and the bit becomes hot, pause, let it cool, and check that you are using a carbide masonry bit with hammer action. Continuing to force a dull or unsuitable bit is more likely to damage the tool than finish the hole.