How do I keep exterior door locks from freezing?

Lubricate before winter, and keep the keyway dry

The best defence is a clean, lightly lubricated lock before the first hard freeze, plus keeping moisture out. Master Lock recommends regular cleaning and lubrication every 3-6 months, and says regular lubrication will also help minimize freezing in cold weather environments.^[1] That guidance is written for its padlocks, but the same logic, water freezing in a dirty keyway, applies to an exterior door lock.

Start by blowing dust out of the keyway with pressurized air.^[1] Then apply lubricant sparingly: a very light spray or a few drops is all that is needed.^[1] Insert the key and open and close the lock several times to distribute it, and wipe the excess off the lock and key.^[1]

Choose the right lubricant

Master Lock recommends a PTFE lock lubricant and says never to use dry graphite or a silicone lubricant, because graphite is often applied in excess, which interferes with part movement.^[1] Another Master Lock winter page does suggest weather-resistant graphite or silicone products, so makers do not fully agree. The safe middle is a small amount of a lock-specific lubricant, never a heavy dose. Schlage's own service manual warns, if you use graphite, not to overdo it or the springs will not have room to compress properly.^[3]

Keep water out

Water gets into a keyway from rain, wet snow and wet keys. A few habits help:

• Wipe a wet key before it goes into the lock.
• Keep the keyway shaded from driven rain where you can, for example with a porch overhang.
• Avoid spraying or hosing the door and lock while washing the house in cold weather.

Master Lock's winter advice for outdoor locks is to keep locks dry by avoiding water exposure and using protective covers, and to use a lock deicer or wrap locks in insulating materials when not in use to guard against freezing.^[2] A small cover over the keyhole is not practical on most front doors, but it can suit a side gate or shed.

If a lock freezes anyway

Cold can make locks stiffen or jam, and moisture and snow increase the risk of corrosion over time.^[2] To free one, Master Lock suggests warming the key and lock gently using a pocket heater or warm water, or using a lock deicer or antifreeze solution.^[2] It also says to avoid using excessive force or open flames, which can damage the lock.^[2]

Two practical cautions follow. Do not soak a door lock or its surround with hot water, because the water can refreeze into ice, and do not force a key, because a snapped key makes a small problem into a locksmith job. Keep a spare can of deicer where you can reach it without going through the frozen door, for example in a coat pocket, because Master Lock suggests having a spare lock deicer or antifreeze spray ready for emergencies.^[2]

Stop and call a pro if

• The key snaps or jams in the lock. Do not keep working it; a locksmith can extract it.
• The lock stays stiff after thawing and lubricating. The cylinder may be worn or corroded; see why a key is hard to turn.
• You are locked out and the door will not open. Call a locksmith rather than forcing the door or lock.
• The bolt does not line up with the strike in cold weather. The door has moved and needs adjusting.

If you need work done, read how to rekey a door lock, see whether locksmiths need a licence in Virginia, and check how much a locksmith costs in Virginia. More topics are in other repair answers and handyman services.

When you are ready, describe the lock problem once and local pros quote it.