How to Drill Mortar Joints Without Damaging Brick

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Drilling into mortar is usually safer for brick than drilling into the brick face, but only if the mortar is sound and you use the right bit and technique. Mortar can crumble, and an oversized or wandering hole may not hold an anchor. The goal is a clean hole in the joint, with enough intact material around it to support the fastener.

Check the wall and choose the joint

Look over the wall before drilling. Avoid loose, cracked, deeply eroded, or recently repaired mortar. If the joint is already failing, a fastener can loosen regardless of the drill you use. For heavy fixtures, uncertain masonry, or a wall with substantial cracking, get advice from a qualified mason or installer before proceeding.

Choose a mortar joint wide enough to keep the bit centered. Many joints are roughly 3/8 inch wide, but dimensions vary. Mark the center with a pencil, then hold the drill in place and check that the bit will not ride onto the brick as it starts. If the joint is too narrow for the anchor’s required hole, don’t force the installation; consider a different mounting location or fastening method.

Choose the drill and bit

For typical small holes in sound mortar, a cordless drill with a sharp carbide-tipped masonry bit is often sufficient. A hammer drill can speed work in hard mortar, but its repeated impacts may break down weak joints. Start without hammer action, then use it only if the bit stalls and the mortar is sound. An impact driver is not the right tool for drilling masonry holes: its rotational impacts are intended for driving fasteners, not controlling a masonry bit.

Use the hole diameter specified by the anchor maker. Common small wall-plug holes are around 1/4 inch, while heavier-duty anchors may call for larger holes. The diameter printed on the bit should match the anchor instructions; guessing can leave the anchor loose or make it impossible to insert. A depth stop is useful, but tape wrapped around the bit can also mark the target depth. Allow a little extra depth for dust, while avoiding unnecessary deep holes.

A basic carbide-tipped masonry bit set is a reasonable buy for occasional light work. For repeated holes, a hammer drill offers a useful speed advantage; for one or two small holes in soft mortar, the drill you already own may be enough.

Drill without chipping the brick

Wear eye protection; masonry dust and chips can fly even from a small hole. Check for hidden wiring or pipes before drilling, especially indoors and near outlets, taps, or radiators. Hold the drill square to the wall, place the bit on the mark, and start slowly with light pressure. Let the bit cut rather than leaning hard on it. Heavy pressure can make the bit wander, overheat, or break through a crumbly joint suddenly.

Once the bit has formed a shallow guide, continue at a steady speed. If using a hammer drill, begin in rotary-only mode. Add hammer action only if progress is poor and the joint remains intact; stop if the mortar starts spalling or the hole widens. Pull the bit out occasionally to clear dust. If the bit binds, stop the drill before withdrawing it. Don’t rock the tool side to side to enlarge the hole: that weakens the joint and creates a poor anchor fit.

Use a small, sharp bit and the lowest practical speed that cuts cleanly. If you hit hard material, don’t immediately switch to a much larger bit or bear down harder. Check that you are centered in mortar, that the bit is suitable for masonry, and that the bit tip is not worn. A blunt bit often produces heat and dust without making useful progress.

Clean the hole and fit the anchor

Remove masonry dust with a hand pump, a suitable vacuum attachment, or a small brush. Dust left in the hole can stop a plug seating fully and reduce its grip. Use the anchor’s stated hole diameter and minimum embedment depth. If the plug goes in loose, spins, or pulls out under light hand pressure, don’t rely on it for a load-bearing installation. A larger anchor is not automatically the fix; it may leave too little sound mortar around the hole.

For light items such as a small picture or cable clip, a correctly sized masonry plug and screw may be enough, provided the mortar is solid. Loads such as shelves, handrails, awnings, and heavy cabinets need a fastening method rated for the material and the expected load. Mortar strength varies, and anchors designed for concrete or brick should not be assumed suitable for a mortar joint. Check the fastener maker’s guidance for mortar or masonry use before choosing a masonry anchor and screw set.

Drive the screw without overtightening. If the anchor turns with it, the hole may be oversized, dusty, or in weak mortar. Remove the fastener and reassess rather than forcing it tighter. For a fresh hole that has crumbled, shift to sound mortar only if the new position keeps adequate distance from the damaged area and the brick edges. Do not patch a loose hole with extra screws or improvised filler and treat it as a reliable structural fixing.

When mortar is the wrong choice

Mortar is the preferred drilling location when it is sound, wide enough, and appropriate for the load. But if the joint is narrow or deteriorated, drilling into the brick may be a better option for some anchors—provided the brick type and fastener instructions allow it. Brick faces can chip or crack, so use a sharp masonry bit, slow starting speed, and no hammer action until you know the material can tolerate it. For fragile, historic, hollow, or unusually soft brick, ask a specialist before drilling.

When the fixing must carry a substantial or safety-critical load, don’t choose a location or anchor based only on convenience. Confirm the wall construction, fastener rating, required embedment, and whether the joint can take the load. A carefully drilled hole cannot compensate for unsound mortar or an anchor that is wrong for the job.