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A door threshold needs fasteners that hold the sill down without cracking the concrete, pulling loose, or hitting a hidden pipe or wire. The right choice depends on the slab, the threshold’s holes, and whether you may need to remove it later. For most solid concrete slabs, masonry screws are the practical default. Concrete nails suit quick work in sound concrete, while sleeve anchors make sense when a threshold has larger holes and needs a stronger mechanical hold.
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Choose the fastener for the threshold and slab
First check the threshold manufacturer’s instructions. Use its specified fastener diameter and length if provided, and don’t enlarge or modify the threshold without a reason. If there are no instructions, measure the thickness of the threshold and any shim or spacer. The fastener must pass through those layers and embed far enough into sound concrete to grip; avoid guessing from overall screw length alone.
Also check what is below the slab before drilling. A garage floor, radiant-heated slab, or concrete over a post-tensioned structure may contain utilities or tension cables. If you cannot confirm that drilling is safe, do not drill until you have checked building plans or consulted a qualified professional.
Compare common concrete fasteners
| Fastener | Best use | What to watch for |
|---|---|---|
| Masonry screw | Most thresholds on solid concrete; removable fastening | Needs a correctly sized pilot hole and sound concrete |
| Concrete nail | Quick installation where the concrete is hard and the threshold has suitable holes | Can bend, glance off, or chip weak concrete; removal is difficult |
| Sleeve anchor | Thresholds with larger holes or a need for a firm mechanical anchor | Requires a larger hole and careful tightening; may be excessive for a light sill |
| Plastic plug and screw | Light-duty work where loads are low and the plug is rated for concrete | Can loosen under repeated foot traffic or movement; not a universal substitute for an anchor |
A masonry screw is often the best balance of holding power, installation effort, and future removal. A box of concrete masonry screws is a reasonable buy for a typical DIY threshold, but match the screw diameter and length to the threshold holes and the screw maker’s instructions. Don’t use a wood screw directly in concrete.
Drilling accurate holes
Mark the hole locations through the threshold, then move it aside. Use a hammer drill with a masonry bit of the diameter specified for the fastener. A regular drill may work in softer concrete and for a small number of holes, but it is slower and can overheat the bit. A hammer drill and masonry bit set is more useful if you expect to drill several holes or work with harder concrete.
Keep the drill square to the slab and drill to the required depth, allowing room for dust at the bottom. Follow the fastener instructions rather than relying on a generic depth rule: pilot-hole diameter and minimum embedment vary by screw. A depth stop or tape wrapped around the bit helps prevent drilling too shallow or too deep. Wear eye protection, hearing protection, and a suitable dust mask; concrete dust is hazardous.
Clear dust from each hole using the method specified by the fastener manufacturer. Dust left in the hole can prevent the screw from cutting properly or keep an anchor from seating. If the hole is oversized, crumbles, or lands in a weak edge, don’t compensate by forcing in a larger screw. Move the hole if the threshold allows, or use a fastening method rated for the actual hole and concrete.
Install without damaging the sill
Set the threshold in place and confirm it sits flat before fastening. If the sill rocks, correct the support with an appropriate noncompressible shim or bedding material rather than tightening one screw until the threshold bends. Keep water management in mind: a door sill must shed water as designed, and an improvised bead of sealant should not block drainage paths.
Drive masonry screws with a drill or impact driver on a controlled setting. Stop when the head is seated; overtightening can strip the concrete threads, snap the screw, or distort a thin aluminum threshold. If the screw spins without tightening, the hole may be too large or damaged. Back it out and repair or relocate the fastening point instead of repeatedly driving it.
Concrete nails avoid predrilling, but they demand a firm, accurate strike and can chip the threshold or surrounding concrete. They are a cheaper option when the job is small, the concrete is known to be sound, and the manufacturer allows them. For a threshold that may need replacement, screws are easier to remove and usually the better choice.
Sleeve anchors expand against the sides of a drilled hole, so they can hold well but need the correct hole size and adequate concrete around them. They are not automatically stronger in every installation: a thin threshold, weak slab edge, or poorly drilled hole can still fail. Use them only when the threshold’s holes and the anchor’s specified embedment suit the application.
A practical buying checklist
Before buying, confirm the threshold hole diameter, total thickness to fasten, concrete condition, and required embedment. Check that the fastener material is suitable for the location; damp exterior entries may call for corrosion-resistant hardware. Buy the matching masonry bit, not one that merely looks close in size, and follow the fastener packaging for drilling, cleaning, and tightening. For a light interior threshold on sound concrete, properly installed masonry screws are usually enough. Spend more on an anchor only when the threshold design or loading calls for it.