Deadlock vs Deadlatch: Which Does Your Door Need?

Walk down almost any street in Lidcombe and you will see the same arrangement on front doors: a knob or lever with a lock above it, or a single lock body with a key on the outside and a turn knob inside. The names people use for these locks are often mixed up. "Deadlock", "deadbolt", "deadlatch", "nightlatch" and "Yale lock" all get used for the same thing in conversation, even though they work quite differently.

Getting the difference right matters, because the type of lock decides how secure your door is when you walk away from it. This guide explains what each lock does, the strengths and weaknesses of each, and how we decide which one suits a particular door.

What a deadlatch is

A deadlatch is a spring-loaded latch with an extra feature. Like an ordinary latch, its bolt has a sloped face, so it springs back and clicks into the strike plate when the door closes. You do not need a key to lock it; closing the door does that.

The "dead" part comes from a small secondary plunger next to the main latch. When the door is shut, that plunger is pressed in by the strike plate and it deadlocks the latch so it cannot simply be pushed back. That is the feature that stops someone slipping a card or a thin tool between the door and frame to push the latch open.

Many deadlatches also have a snib or button on the inside that holds the latch open, or locks the inside handle so it cannot be opened without a key.

Strengths of a deadlatch

• Locks automatically every time the door closes.
• Convenient for households where people come and go often.
• Better protection against slipping than a plain spring latch.

Weaknesses of a deadlatch

• The latch bolt is usually short and spring-loaded, so it does not go deep into the frame.
• If the plunger is not aligned with the strike, the deadlocking feature does not engage and the latch can be slipped.
• It is easy to lock yourself out, because the door locks behind you.

What a deadlock (deadbolt) is

A deadlock, also called a deadbolt, has a solid rectangular bolt with no spring. It only moves when you turn a key or a thumb turn. When it is thrown, it sits deep into the frame and cannot be pushed back by force on the bolt itself.

There are two common styles:

• Single-cylinder deadbolts have a key outside and a thumb turn inside.
• Double-cylinder deadbolts need a key on both sides.

Strengths of a deadlock

• A longer, solid bolt that resists forcing.
• Cannot be slipped, because it has no sloped face.
• You choose when it is locked, so you cannot accidentally lock yourself out by pulling the door shut.

Weaknesses of a deadlock

• It only protects the door when someone remembers to lock it.
• A double-cylinder deadbolt can trap people inside in a fire if the key is not nearby. We always discuss safe exit before fitting one.
• Its strength depends on the frame and strike. A strong bolt in a weak frame can still be kicked through.

Why many front doors use both

The combination most Sydney homes end up with is a deadlatch for everyday convenience and a deadbolt for when the house is empty or at night. The deadlatch means the door is never simply left on the latch; the deadbolt adds the real resistance to force.

Some single lock bodies, often called entrance sets or deadlatches with deadlocking functions, try to do both jobs in one unit. Many are perfectly good. What matters is the quality of the product and how well it is fitted.

Which is better for your door?

There is no single right answer. These are the questions we ask on site:

How is the door used?

A busy family home where children come and go benefits from a deadlatch so the door locks itself. A home that is empty all day benefits most from a deadbolt that is thrown every morning.

What is the door made of?

A deadbolt needs a solid door and a solid frame. Hollow-core doors, sometimes found as back doors in older renovations, may not be suitable for a deadbolt without reinforcement or a door replacement.

What does the frame look like?

A strong bolt is only as good as the strike plate and the timber around it. We often recommend a reinforced strike plate with long screws that reach the wall framing. This is one of the most cost-effective upgrades on any door. See security locksmith.

Who lives there?

If anyone in the house would have trouble finding a key in an emergency, a double-cylinder deadbolt is not a good idea. A single-cylinder deadbolt with an inside turn is safer for most homes.

Is it a rental?

In a rented home, changing locks usually needs agreement between landlord and tenant. Our guide to NSW landlord and tenant lock rules explains why.

Shops and offices

Commercial doors follow the same principles, with extra considerations. A shopfront may need a lock that allows free exit from inside for safety while staying locked from outside. Glass and aluminium doors use narrow-stile locks designed for their thin frames. Our commercial locksmith page covers those.

Signs your current lock needs attention

• The key has to be jiggled or the door pushed before the lock will turn.
• The latch does not catch every time the door closes.
• The deadbolt will not throw fully unless you lift or push the door.
• The lock feels loose on the door.
• You can see daylight between the door and frame near the lock.

Most of these are alignment problems that can be fixed without new hardware. Our lock repair page explains what is usually involved.

Upgrading from a latch to a deadbolt

If your front door only has a spring latch or an old rim lock, adding a deadbolt is one of the most useful upgrades available. It involves drilling the door, cutting a pocket for the bolt in the frame and fitting a strike plate. Done properly, it looks tidy and works smoothly for years. See door lock installation.

Common questions

Is a deadlatch enough on its own? For a well-fitted, good-quality deadlatch on a solid door, it is much better than a plain latch. Adding a deadbolt gives better resistance to force.

Can a deadlatch and deadbolt use the same key? Often, yes, if both come from a compatible range or are rekeyed to match.

Are deadbolts hard to use? No. A single-cylinder deadbolt is a quarter or half turn of a thumb knob from inside.

Talk to us about your door

If you are not sure what is on your door now, take a photo of it from both sides and send it to [email protected], or call 02 4503 6922. We work across Lidcombe, Auburn, Berala, Regents Park, Homebush and Strathfield, open 7 days, 7:00 AM to 12:00 AM, and we quote before we start. You can also request a quote.