Which screw should I use in masonry?
Which screw should I use in masonry?
A concrete screw into a precisely sized hole, or a plug and screw — and hollow block needs a different anchor entirely.
The substrate decides the fixing far more than the load does. Solid concrete takes almost anything; dense engineering brick takes most things; lightweight aerated block, perforated brick and old lime-mortared walls crumble under any expansion anchor, and the answer there is a resin anchor with a sleeve that lets the resin key into the voids. Mortar joints are always weaker than the bricks either side, so a load-bearing fixing goes into the brick. The commonest practical failure is a hole drilled slightly oversize by a wandering bit: the plug spins, the screw never tightens, and the usual remedy — a longer screw — does nothing. Drill again nearby, or move up a size.
The options, ranked
| Option | Good at | Bad at |
|---|---|---|
| Concrete screw | Cuts its own thread in a drilled hole with no plug, is removable, and holds well in solid concrete and dense brick. | Hole size is critical to within a fraction of a millimetre, and it is much weaker in soft or perforated brick. |
| Nylon plug and screw | Cheap, forgiving of an imperfect hole, and adequate for the great majority of domestic fixings. | The plug spins in an oversized hole, and its rating drops sharply in mortar. |
| Sleeve or through-bolt anchor | High load capacity in solid concrete for heavy brackets and structures. | Expands as it tightens, so it cracks the material near an edge or in soft brick. |
| Chemical anchor with a mesh sleeve | The right answer in hollow block, perforated brick and old crumbling masonry, where expansion anchors have nothing to push against. | Two-part resin, hole cleaning matters enormously, and it takes time to cure. |
Technique that changes the outcome
- Match the drill diameter exactly to the fixing, and use a sharp bit so the hole is not oversize
- Drill deeper than the fixing so debris has somewhere to go, then blow or vacuum the hole
- Fix into brick rather than mortar wherever load is involved
- For resin anchors, follow the blow-brush-blow cleaning sequence and observe the cure time
What goes wrong
- Expansion anchors in aerated block or perforated brick
- Fixing into mortar joints for anything that carries weight
- Hammer drilling soft or historic brickwork, which blows out the face
Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.
Other screw questions
| For | Use |
|---|---|
| Wood | A pilot hole matching the screw's core diameter in the lower piece and a clearance hole in the upper one — that is what makes a joint tight. |
| Decking | Stainless steel — 304 inland, 316 near the coast — or a screw specifically rated for modern treated timber, which eats ordinary zinc plating. |
| Plasterboard | Coarse-thread bugle-head drywall screws into timber studs, fine-thread into metal studs — and never use them for anything structural. |
| MDF | A straight-shank MDF screw with a parallel thread, always into a pilot hole — the edge splits without one. |
| Sheet metal | A self-drilling (Tek) screw with a drill point matched to the material thickness, or a self-tapping screw into a correctly sized pilot hole. |
| Chipboard | A twin-thread chipboard screw with an unthreaded shank under the head, so it pulls the joint together instead of bursting the board. |
| Plastic | A thread-forming screw designed for plastic, or a heat-set threaded insert where the joint will be undone more than once. |
| Roofing sheets | A hex-head screw with a bonded EPDM washer, driven until the washer just spreads — no further. |
| Brass hardware | Cut the thread with a steel screw of the same size first, wax the brass one, and use a driver that fits the slot exactly. |
Common questions
- Which screw should I use in masonry?
- A concrete screw into a precisely sized hole, or a plug and screw — and hollow block needs a different anchor entirely.
- What should I avoid?
- Expansion anchors in aerated block or perforated brick Fixing into mortar joints for anything that carries weight Hammer drilling soft or historic brickwork, which blows out the face
Related pages
- Which screw and pilot hole should I use for wood? A pilot hole matching the screw's core diameter in the lower piece and a clearance hole in the upper one — that is what makes a joint tight.
- Which screw should I use for decking? Stainless steel — 304 inland, 316 near the coast — or a screw specifically rated for modern treated timber, which eats ordinary zinc plating.
- Which screw should I use for plasterboard? Coarse-thread bugle-head drywall screws into timber studs, fine-thread into metal studs — and never use them for anything structural.
- Which screw should I use in MDF? A straight-shank MDF screw with a parallel thread, always into a pilot hole — the edge splits without one.
- Which screw should I use for sheet metal? A self-drilling (Tek) screw with a drill point matched to the material thickness, or a self-tapping screw into a correctly sized pilot hole.
- Which screw should I use in chipboard? A twin-thread chipboard screw with an unthreaded shank under the head, so it pulls the joint together instead of bursting the board.
- Which screw should I use in plastic? A thread-forming screw designed for plastic, or a heat-set threaded insert where the joint will be undone more than once.
- Which screw should I use for roofing sheets? A hex-head screw with a bonded EPDM washer, driven until the washer just spreads — no further.
- How do I drive brass screws without snapping them? Cut the thread with a steel screw of the same size first, wax the brass one, and use a driver that fits the slot exactly.
- Which drill bit should I use for masonry? Drill bit
Sources
- Typical range compiled from manufacturer specifications — At One Place