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Conduit straps look simple, but a loose strap can let conduit rattle, pull away from a wall, or stress the wiring inside. The reliable method is to match the fastener to the masonry, drill a straight hole to the anchor’s specified diameter and depth, and tighten the strap without crushing the conduit.
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Choose the fastener for the masonry
“Masonry” can mean solid concrete, brick, or hollow concrete block, and the same fastener does not work equally well in all three. For a light conduit run on sound solid concrete or brick, a masonry screw installed in a correctly sized pilot hole is often the quickest option. Use a listed screw and follow its packaging for bit diameter, embedment, and edge-clearance requirements.
Plastic expansion plugs paired with compatible screws are inexpensive and can be adequate for light-duty indoor conduit where loads are modest. They are less forgiving of oversized holes, crumbly masonry, heat, and repeated movement. For hollow block, a plug intended for solid concrete may expand into an empty cell and hold poorly; choose a fastening system rated for hollow masonry or position the attachment in a solid web when practical.
For heavier conduit, vibration, or a location where failure could cause damage, consider a rated masonry anchor matched to the substrate and load. The masonry screws and concrete anchors available in hardware kits vary in diameter, length, and approved base materials, so check the package rather than selecting by appearance alone.
| Fastener type | Best fit | Main trade-off |
|---|---|---|
| Masonry screw | Light to moderate loads in sound solid concrete or brick | Needs an accurate pilot hole; can strip or loosen if the hole is oversized |
| Plastic plug and screw | Light indoor runs and simple repairs | Low cost, but sensitive to hole size and weak or hollow masonry |
| Rated mechanical anchor | Higher loads when the anchor is approved for the substrate | More installation steps; requires correct diameter, depth, and edge distance |
Gather tools and lay out the run
Use a hammer drill with a carbide-tipped masonry bit for concrete and most brick. A regular drill may work in soft brick with a small bit, but it is slower and can overheat the bit; dense concrete is a poor place to force it. A cordless hammer drill and masonry bit set is a sensible purchase if you have several holes to make. For a one-off, renting a hammer drill or borrowing one is usually cheaper than buying a tool for a single run.
Check for concealed wiring, plumbing, and other services before drilling. Mark the strap holes with the strap held in place, and keep the conduit straight with a level or chalk line. Strap spacing depends on conduit type, size, orientation, and electrical-code requirements; use the applicable code and manufacturer instructions instead of assuming one universal spacing. Place supports near boxes and fittings as required, while leaving room for bends and connections.
Plan holes away from masonry edges and mortar joints where possible. Brick faces can split near an edge, and old mortar may crumble under an anchor. If the wall is visibly cracked or deteriorated, move the attachment or use a fastening plan appropriate to the condition rather than relying on a stronger screw alone.
Drill clean, correctly sized holes
Wear safety glasses and hearing protection. Masonry drilling creates fine silica-containing dust; avoid breathing it by using suitable dust control and respiratory protection for the job. A vacuum attachment or a helper collecting dust at the bit can reduce mess, but follow the tool and safety-equipment instructions.
Fit the bit size specified for the chosen fastener. Set a depth stop, or mark the bit with tape, so the hole is deep enough for the required embedment plus a little room for dust. Drill perpendicular to the wall at a controlled speed. Let the hammer action do the work; pushing hard can overheat the bit, make the hole wander, or chip the brick face. If the bit stops cutting, withdraw it periodically to clear dust.
Do not use a bit that is merely “close” in size. A hole that is too small can prevent a screw from seating or damage an anchor; one that is too large can leave a masonry screw with little grip. Clean the hole according to the anchor maker’s directions. Dust left inside can reduce holding strength, especially for anchors that depend on close contact with the hole wall.
Attach the straps without damaging the conduit
Hold the strap over the hole and start the fastener by hand so it enters straight. Tighten with a hand driver or a drill/driver on a low setting. An impact driver can be useful for masonry screws, but its repeated blows can overdrive a small screw, strip the hole, or bend the strap before you notice. If using one, start slowly and finish by hand.
Tighten until the strap sits firmly against the wall and holds the conduit in position. Do not crush plastic conduit or clamp it so tightly that it cannot move as the installation requires. A visibly bowed strap, spinning fastener, or conduit dent is a sign to stop. If a masonry screw spins without tightening, remove it and assess the hole; moving to a larger fastener may not be acceptable unless the strap and substrate can accommodate it. Use a fresh hole with the specified size, or select a compatible anchor.
Check the installation
After fastening each strap, tug the conduit gently and check for movement. The strap should not rock, the fastener should not turn, and the conduit should remain aligned. If the anchor pulls out, do not reinstall it in the same damaged hole. Shift to sound material while respecting edge distance and required support spacing.
For ordinary indoor work in sound solid masonry, correctly installed masonry screws are often the practical middle ground between cheap plugs and more involved anchors. In hollow block, weak brick, or a higher-load location, the substrate—not the price of the fastener—should drive the choice. When the installation is part of a regulated electrical system, verify the support method and spacing against local code and the conduit manufacturer’s instructions.