Deadlock vs Deadlatch: Which Lock Does Your Door Need?

Walk into any hardware store and you will see shelves of locks labelled deadlock, deadlatch, deadbolt and entrance set. They can look almost identical in the packet, yet they behave very differently on a door. Choosing the wrong one can leave you less secure than you think, or make it harder to get out in an emergency. This guide explains the difference in plain language and helps you decide what your front, back and side doors actually need.

The short answer

A deadlatch locks automatically when the door closes, like a spring latch, but its bolt cannot be pushed back from outside with a card or tool once it is deadlocked. A deadlock (often called a deadbolt) uses a solid bolt that only moves when you turn a key or snib. It does not lock by itself.

Many homes in Burwood East have both on the front door: a deadlatch for everyday convenience and a separate deadbolt for extra strength at night or when away.

How a deadlatch works

A deadlatch has a sloped latch bolt that springs into the strike plate when the door closes. Next to it is a small trigger bolt, sometimes called an auxiliary bolt. When the door closes, the strike holds the trigger in, and that locks the latch bolt so it cannot be slipped back with a credit card or thin tool.

Most residential deadlatches also have a deadlocking function. When you lock it with the key from outside, or press the button on the inside handle, the inside handle can no longer open the door without a key. That stops someone breaking a glass panel and reaching in to open it.

Strengths of a deadlatch

• The door locks every time it closes, so you never forget.
• Easy to open from the inside in normal mode.
• Good everyday protection against slipping the latch.

Weaknesses of a deadlatch

• It is easy to lock yourself out, because the door locks behind you.
• The bolt is shorter than a deadbolt, so a weak frame can give way under force.
• If deadlocked from inside with a key, it can slow your exit in an emergency.

Lockouts caused by deadlatches are the most common call our lockout service receives, especially from townhouses and units.

How a deadlock or deadbolt works

A deadbolt throws a solid, square-ended bolt deep into the frame. It does not spring. It only moves when you turn the key from outside or the key or turn knob from inside. Because the bolt is longer and solid, a properly fitted deadbolt with a reinforced strike plate is much harder to force than a latch.

Single and double cylinder

A single-cylinder deadbolt has a key outside and a turn knob inside. A double-cylinder deadbolt needs a key on both sides. Double cylinders stop someone reaching through glass to unlock the door, but they can trap people inside if the key is not nearby during a fire.

Strengths of a deadbolt

• Strong resistance to kicking and forcing when fitted to a solid frame.
• Cannot be slipped with a card.
• Simple and reliable.

Weaknesses of a deadbolt

• Only secure when you remember to lock it.
• Key-only inside versions can be a fire safety risk.
• Strength depends heavily on the frame and strike.

Safety first: getting out quickly

The main safety question is how fast everyone in the house can get out in a fire. Locks that need a key on the inside are a real risk if the key is not in the lock or nearby. For the main exit doors we usually recommend:

• A deadlatch that opens freely from inside in normal mode, or
• A single-cylinder deadbolt with an internal turn knob.

If you prefer a key-locking inside function for glass doors, keep the key in a fixed, known place near the door, out of reach from outside. Our residential locksmith service talks through how your household uses each door before recommending anything.

Which doors need which lock

Front door

For most homes the best combination is a quality deadlatch with deadlocking plus a separate deadbolt above it. The latch handles everyday coming and going, and the deadbolt adds strength at night and when you are away.

Back door

Back doors are often hidden from the street, so strength matters more. A well-fitted deadbolt with a reinforced strike is the priority. Many back doors in older Forest Hill and Vermont South homes still only have a basic latch.

Garage internal door

If a garage remote is stolen from a car, the door from the garage into the house becomes the main barrier. A deadbolt here is worth considering.

Sliding doors

Sliding doors do not take a deadlatch or deadbolt in the usual way. They need sliding door locks, keyed bolts and anti-lift protection. Our guide to sliding door security covers these.

The frame matters as much as the lock

Most forced entries do not defeat the lock mechanism. The frame splits around the strike plate. A strong deadbolt held by two short screws in soft timber will fail long before the lock does. That is why a security locksmith fits reinforced strikes with long screws that reach the wall framing.

Signs your current lock needs attention

• The deadbolt needs the door pushed or lifted before it will throw.
• The latch does not catch every time the door closes.
• The key is stiff or only works at a certain angle.
• The handle droops or spins.
• The trigger bolt does not deadlock the latch.

These are usually lock repair jobs rather than replacements.

Rentals and minimum standards

Victorian rental minimum standards require external entry doors to be able to be secured with a functioning deadlock, unless an exemption applies. In practice that usually means a deadlatch with a deadlocking function or a deadbolt. Rental providers should check current requirements with Consumer Affairs Victoria, and renters should not change locks without following the rules covered in our landlord and tenant lock guide.

Upgrading without replacing the door

Most upgrades can be fitted to an existing door. A deadbolt can usually be added above an existing deadlatch, and a better deadlatch can often replace an old one in the same cut-out. We check the door thickness, backset and condition before suggesting anything.

Keying them alike

If you add a deadbolt to a door that already has a deadlatch, ask for both to be keyed alike. One key for both locks, and ideally for every external door, makes life easier. See door lock installation for more.

Summary

Talk it through with a local locksmith

If you are not sure which lock suits your door, call 03 4422 2837 or request a quote. We are at 50 Middleborough Rd, Burwood East, open 7 days from 8:00am to 7:00pm (Friday until 7:30pm), with emergency lockouts 24/7.