How do I cut through timber with nails or screws in it?

Reclaimed timber, old floorboards, pallets, skirting being taken off and any structure being altered all contain metal you cannot see. A carbide-tipped blade is very hard and very brittle, which is exactly wrong for hitting steel; a bi-metal blade is the opposite compromise and survives.

Safety

What you'll need

• Bi-metal or nail-embedded blade for your saw
• Eye protection
• Magnet or metal detector
• Nail punch and pincers (optional)
• Cable and pipe detector, for fixed structures (optional)

Step by step

1. Find the metal first.Run a strong magnet over the timber, or use a metal detector. Mark every hit. On reclaimed boards, look for the pattern — nails follow joist lines and are usually paired.
2. In a fixed structure, check it is not a service.A detector that finds metal in a wall or floor may be finding a cable or a pipe. Use a proper cable and pipe detector, check the circuit, and isolate before cutting. Do not assume.
3. Remove the fixing if you can.Pincers, a claw hammer levered against a block, or a nail punch driven right through. Removing it takes a minute and saves the blade and the risk entirely. Screws can often be backed out even when the head is damaged, with a screw extractor or by cutting a slot.
4. If it must be cut, pick the right blade.Reciprocating saw: a nail-embedded demolition blade, typically 8–10 TPI bi-metal, which will cut timber and steel together. Multi-tool: a bi-metal or carbide plunge blade. Jigsaw: a bi-metal blade in the 100 series or a specific nail-cutting blade. Hand saw: only a hacksaw, on the nail alone.
5. Never take a TCT circular saw blade into metal.Carbide is brittle. A tip that hits a nail can shatter, and the fragments leave at rim speed. Even where the blade survives, the tips are chipped and the blade is finished.
6. Slow down through the metal.Reduce speed, reduce pressure and let the teeth work. Forcing through a nail overheats the teeth and anneals them, after which the blade is soft and useless.
7. Support the work firmly.The tool will snatch when it meets the metal. Clamp the timber, brace the tool, and keep your body out of the line it would travel if it jumped.
8. Expect to change the blade.Even the right blade dulls quickly cutting through fixings. Budget for it, keep a spare in the case, and change it as soon as it starts to smoke or push rather than cut.

Tips

• Old cut nails in Victorian floorboards are tapered and square in section. They hold ferociously and shear rather than pull — cutting them with a multi-tool is usually the only way to lift the board intact.
• If a blade suddenly stops cutting in reclaimed timber, assume it has hit metal rather than that it has gone blunt on wood.
• Grit and sand embedded in reclaimed timber is almost as hard on blades as nails, especially in anything that has been outside.

Alternatives

• Punch the nail through and cut clear: A nail punch driven right through the board leaves the nail in the offcut or in the joist below. Fastest and cheapest option where the fixing is accessible.
• Cut the nail with a multi-tool first: Slide a bi-metal blade between two pieces of timber to shear the fixings, then separate them. This is the standard way to free skirting, treads and nailed cladding without damage.
• Angle grinder with a metal cutting disc: For heavy embedded steel, bolts or rebar. Fast, but throws sparks into sawdust, which is a real fire risk in a working space.
• Buy a dedicated demolition blade set: If you are working through a reclaimed floor or a stud wall, a pack of nail-embedded reciprocating blades treated as consumables is far cheaper than ruining good blades one at a time.