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A concrete retaining wall is a demanding place to drill: the bit must cut through hard aggregate, may encounter reinforcing steel, and needs to make a hole deep enough for the anchor without wandering. The right choice depends less on a “masonry” label than on the drill, hole diameter, wall material, and anchor instructions.
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Choose the bit for the drill and hole
For small holes in ordinary concrete, a carbide-tipped masonry bit used in hammer mode is usually the practical starting point. Its cutting tip is brazed carbide, while the flutes carry dust out of the hole. Match the bit’s diameter to the anchor manufacturer’s stated hole size; a hole that is too large can leave an anchor loose, and one that is too small may prevent it from seating.
A standard round-shank bit fits many cordless hammer drills and three-jaw chucks. For larger holes or frequent concrete drilling, an SDS-Plus rotary hammer and SDS-Plus bit are more efficient: the hammer mechanism delivers blows through the bit rather than relying on the drill’s chuck and hammering action. Check the tool’s chuck before buying. SDS bits do not fit a standard three-jaw chuck.
Look for a carbide-tipped masonry bit set for occasional anchor holes in the common small sizes. A set is convenient, but don’t assume every included diameter suits your anchors; verify the packaging and anchor directions first.
Bit options at a glance
| Bit type | Best fit | Trade-off |
|---|---|---|
| Standard carbide masonry bit, round shank | Occasional small holes with a hammer drill | Affordable and widely available; slower and more prone to wear in hard concrete |
| SDS-Plus carbide bit | Repeated holes or larger holes with a rotary hammer | Drills efficiently, but requires an SDS-Plus tool |
| Four-cutter SDS bit | Rebar-prone concrete or demanding anchor work | More reliable cutting geometry, usually at a higher price |
| Diamond core bit | Large, clean openings where the tool and setup support coring | Specialized and generally unnecessary for ordinary wall-anchor holes |
When to upgrade to SDS-Plus
A compact cordless drill with hammer mode can handle a handful of holes, especially in softer concrete or concrete block. It will often slow down as hole diameter, depth, or aggregate hardness increases. If drilling one hole takes several minutes, the bit gets very hot, or the tool’s hammer action feels like it is barely advancing, stop and reassess rather than forcing it.
For multiple holes or holes around 3/8 inch and larger, a cordless SDS-Plus rotary hammer paired with the correct SDS bit is often a better buy than repeatedly burning through inexpensive round-shank bits. A four-cutter bit can also be worthwhile where the hole must stay round and the wall may contain rebar. For a single small hole in sound concrete, though, that upgrade is usually unnecessary.
Don’t use an impact driver as though it were a hammer drill. It is designed to turn fasteners and needs a bit with the correct impact-driver shank; it does not provide the axial hammering action needed to drill concrete efficiently. Use a hammer drill or rotary hammer instead.
Drill the hole without damaging the wall
First check for buried electrical conduit, pipes, and reinforcement. Retaining walls can contain rebar, and drilling blindly into a reinforced section can damage the wall or the bit. Consult construction drawings if available; otherwise, scan the intended area with an appropriate detector and choose a safe location. Do not cut reinforcement to make an anchor fit.
Mark the hole and use a depth stop or tape on the bit. Many small concrete anchors need a hole only a few inches deep, but the anchor’s instructions determine both diameter and depth. Keep the drill square to the surface. Start slowly to prevent the tip skating, then use steady pressure rather than leaning your full weight on the tool. Let the bit cut; excessive force can overheat it, wear the carbide, or stall the drill.
Clear concrete dust from the hole as directed by the anchor maker. Dust left at the bottom can stop an anchor from seating properly, and some adhesive anchors require especially careful cleaning. Wear eye protection and a suitable dust mask or respirator; concrete dust contains respirable silica. Avoid dry drilling where dust cannot be controlled. Follow the tool and anchor manufacturers’ safety instructions.
What to do if the bit hits rebar
A sudden stop, metallic sound, or abrupt change in drilling resistance may mean the bit has reached steel. Release the trigger and pull the bit out; do not keep hammering against the bar. Rebar can quickly blunt a standard carbide tip, and hammering into it may damage the bit or tool. Move the hole only if the anchor layout and wall structure allow it. If the design requires that location, ask an engineer or qualified contractor how to proceed rather than cutting the steel.
Also watch for a bit that wanders, produces unusually fine dust without advancing, or has a chipped tip. A dull bit turns drilling into a long, hot job and can leave an oversized or ragged hole. Replace it when it no longer cuts cleanly; the small saving from stretching its life is not worth a poor anchor fit.
A practical buying checklist
Before ordering, confirm the drill’s chuck type, the anchor’s required hole diameter, and the depth you need. Buy a bit rated for concrete and compatible with the tool—not merely a general-purpose bit labeled for several materials. For a few small holes, an inexpensive carbide set is fine if it is sharp and correctly sized. For repeated work, hard concrete, or larger holes, step up to an SDS-Plus rotary hammer and a quality SDS bit. The right match saves time and helps the anchor fit as intended.