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A cable pass-through is a hole just large enough for the cable and its connector, with a sleeve or bushing to protect the cable from the brick’s sharp edges. The main risks are drilling into a hidden wire or pipe, cracking the brick, and making a hole that slopes the wrong way or ends up too large. Choose the route and drill bit before you start; enlarging a misplaced hole is not a good fix.
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Plan the route and hole size
Measure the cable’s thickest point, including any plug that must pass through. Choose a masonry bit slightly larger than that measurement, or use a masonry hole saw for a larger, cleaner opening. A 10–12 mm bit may suit a bare cable; a connector can require a 20–30 mm hole or more. Check the sleeve or grommet’s outside diameter too—the hole must fit it, not just the cable.
Mark the hole on the brick, not in the mortar joint. Brick is generally more stable for a small pass-through, while mortar can crumble and leave a loose, uneven edge. Check both sides of the wall if accessible. Keep clear of outlets, switches, taps, radiators, and visible service routes; use an appropriate detector, but treat its reading as a warning aid rather than proof that the wall is clear. If you cannot rule out a service line, stop and get qualified help.
Choose the drill and bit
For a small hole in sound brick, a corded or cordless drill with a hammer function and a sharp masonry bit is usually adequate. A compact hammer drill is easier to control than a heavy rotary hammer for holes around 6–12 mm. For a hole above roughly 16 mm, repeated holes, or dense brick, a rotary hammer with an SDS masonry bit or hole saw can make the job faster, but it removes material aggressively and is easier to overdo.
A standard drill without hammer action can work in soft brick with a small bit, but expect slow progress. Do not use an impact driver as your main drilling tool: its impacts are rotational, not the forward blows a masonry bit needs, and it is difficult to control for a neat opening. For a one-off small pass-through, borrowing a hammer drill may be cheaper than buying a rotary hammer. If you need to buy, compare cordless hammer drills with the bit size and wall material you actually have in mind.
| Tool | Good fit | Trade-off |
|---|---|---|
| Standard drill | Small hole in soft brick, patient drilling | Slow; may polish the hole without cutting efficiently |
| Hammer drill | Typical small cable hole in brick | Less effective than an SDS rotary hammer in hard masonry |
| Rotary hammer | Larger holes, dense brick, frequent masonry work | Can chip or crack brick if pushed hard or used with an oversized bit |
Use a carbide-tipped masonry bit for ordinary holes. For a wide pass-through, a purpose-made masonry hole saw is cleaner than making many overlapping holes, but it costs more and requires a compatible arbor and drill. Search for a masonry hole saw kit only if its stated diameter and shank match your tool.
Drill safely and keep the hole controlled
Wear safety glasses, hearing protection, and a suitable dust mask. Brick dust is harmful to breathe; keep people away from the drilling area and collect dust as it falls. Do not hold a vacuum nozzle close to a rotating bit unless its placement is safe and stable. Secure a ladder or work platform before drilling overhead, and keep a firm two-handed grip where the tool allows.
Set the drill to hammer mode for ordinary masonry drilling, but begin without hammer action if the brick surface is brittle or glazed. Hold the bit square to the wall and start slowly to establish the position. Then drill at a steady pace with light pressure. Let the bit cut; leaning heavily can overheat it, bind the tool, or break the brick around the entry point. Withdraw the bit every few centimetres to clear dust. If it stops advancing, do not keep forcing it—clear the hole, check the bit, and reassess whether you have hit unusually hard material or something you should not drill through.
For a pass-through between indoors and outdoors, angle the hole slightly downward toward the exterior, around 5–10 degrees, so rainwater is less likely to run inward. A long bit can wander, so start with a short masonry bit or guide hole if needed, then switch to the required length while keeping the same angle. Measure the wall thickness and mark the bit with tape or a depth stop. Stop just before breaking through, then finish carefully from the other side if access permits. This reduces breakout and spalling around the exit.
Fit the sleeve and seal the opening
Remove loose dust and fragments, then check that the cable and sleeve fit without force. A plastic or rubber grommet protects the cable where it passes through the masonry; for a larger opening, fit a short sleeve or conduit. Do not leave a cable rubbing directly against a rough brick edge. If you need a matching fitting, look for cable pass-through grommets sized for both the hole and cable.
On an exterior wall, seal around the sleeve with an exterior-rated sealant compatible with the wall and fitting, while keeping the sleeve’s interior clear. Follow the sealant manufacturer’s instructions and avoid sealing in a way that traps water. Do not use expanding foam as the sole weather seal or as a substitute for a proper cable sleeve. If the cable is mains wiring, its route, protection, and any required building or electrical rules are different from those for low-voltage data cables; use a qualified electrician when in doubt.
Common mistakes to avoid
A hole that wanders often starts with a blunt bit, excessive pressure, or a poor starting mark. Replace a worn bit and begin slowly. Crumbling brick usually means the hammer action or feed pressure is too aggressive, or the hole is too close to an edge; move the route if possible and reduce force. If the bit binds, release the trigger before trying to free it. A clean, slightly oversized hole with a fitted sleeve is safer than forcing a cable through a tight opening, but drilling a much larger hole creates more repair and sealing work.