Fix a Stiff Door Lock That's Hard to Turn

The most common cause is a dry or dirty lock cylinder — most stiff locks are fixed in under 5 minutes with the right lubricant, no tools needed. The critical mistake people make is using WD-40, which is a degreaser, not a lubricant — it will make the problem worse over time by stripping existing lubrication.

Step 1 — Diagnose the Cause (30 seconds)

• Key turns hard but latches fine: Lock cylinder is dry or dirty → lubricate it.
• Key turns fine but latch won't move: Latch mechanism is binding → lubricate the latch bolt.
• Key is hard AND the door binds: Door is misaligned with the strike plate → hinge or frame issue.
• Key is visibly worn or bent: Get a duplicate cut from the original — a worn key causes false stiffness.

Step 2 — Lubricate the Lock (Free Fix First)

1. Rub a graphite pencil (#2) along both sides of your key — this deposits dry graphite into the cylinder. Insert and remove the key 8-10 times to distribute it. This works immediately for light stiffness.
2. For moderate stiffness, use dry graphite spray or PTFE (Teflon) lubricant — insert the nozzle into the keyhole and spray a short burst, then work the key in and out.
3. Spray latch lubricant into the latch bolt hole on the door edge and operate the handle 10 times.

Step 3 — If It's Still Stiff (Door Alignment)

1. Check the strike plate on the door frame — if the latch doesn't enter cleanly, the door has shifted. Tighten hinge screws first (they loosen over time).
2. If hinge screws spin freely, the wood is stripped — insert a wooden toothpick with wood glue, let dry, re-drive the screw. This is the proper fix before calling a carpenter.
3. If the door frame has warped or swelled (common in Canada with humidity changes), sand the latch contact point on the strike plate or slightly widen the strike plate hole with a chisel.

When to Replace the Lock

• Key is cracked, bent, or badly worn
• Cylinder has visible rust inside
• Lock is more than 15-20 years old with no service history
• Lubricating makes no difference after 2-3 attempts

Pro tip: In Canadian winters, exterior lock stiffness is often caused by moisture freezing inside the cylinder. Use a dedicated lock de-icer (contains methanol) — never hot water, which refreezes and worsens the jam. Going forward, a small amount of PTFE spray each fall prevents winter seizure entirely.