French doors are as secure as any other external door once the inactive leaf is properly bolted, the hinges are protected and the glass is laminated. Their reputation comes from the fact that two leaves meet in the middle with no frame between them, so the join is the natural place to apply force. Everything below is about closing that join and the hinge line, which are the two vulnerabilities a sliding door does not have.
Why French doors get a bad reputation
A standard hinged door closes into a fixed frame on all four sides. Every edge is supported by something structural.
A pair of French doors closes into a frame on three sides only. The fourth side of each leaf meets the other leaf, and that meeting line runs the full height of the opening with nothing behind it but the two door stiles.
If the inactive leaf is not secured to the head and sill, that join can be forced apart. The lock on the active leaf is engaging into a door that is itself free to move, which is the security equivalent of locking a gate to a fence post that is not in the ground.
Properly bolted, the inactive leaf becomes part of the frame and the join is no longer a weak point. Most French door insecurity comes down to that one detail.
The active leaf and the inactive leaf
In a standard pair, one leaf is used daily and the other stays closed.
The active leaf carries the handle and the primary lock. It opens and closes normally, and it locks into the inactive leaf or into the frame depending on the configuration.
The inactive leaf, sometimes called the passive or fixed leaf, is held closed by bolts at the head and sill. It opens only when the full width is needed, for moving furniture or for ventilation.
Understanding which leaf is which matters, because the security measures differ for each and most owners only think about the one they use.
Securing the inactive leaf
This is the most important thing on the page.
Flush bolts or shootbolts are mortised into the edge of the inactive leaf and throw vertically into the head frame above and the sill below. A lever or slide on the leaf edge operates them, accessible only when the active leaf is open, which is by design.
Three details determine whether they actually work.
Both bolts, every time. A leaf bolted only at the top can be levered at the bottom, and the reverse. They are fitted in pairs.
Full engagement. A bolt that enters its keeper by a few millimetres provides far less resistance than one seated fully. If a bolt feels stiff, the cause is usually debris in the keeper hole or a leaf that has dropped, not the bolt itself.
Keeper depth. The hole in the sill and the plate in the head need to be deep enough to hold the bolt properly. Shallow keepers are a common shortcut on cheaper installations.
Automatic flush bolts engage and release themselves as the active leaf opens and closes. They remove the possibility of forgetting, which on a door most people rarely open fully is a real risk.
The astragal
The astragal is the overlapping profile fitted to the meeting stile of one leaf, covering the gap where the two doors meet.
It does two jobs. It closes the gap against weather and draught, and it prevents a tool or card being slipped between the leaves to reach the latch. A pair of French doors without an astragal has a visible vertical gap running the full height, and that gap is an invitation.
On aluminium French doors the astragal is usually integral to the stile section rather than an applied strip. Worth confirming that the leaves overlap rather than simply butting together.
The hinge vulnerability
This is the point most articles miss, and it is specific to hinged doors.
Australian French doors frequently open outward, which suits our climate and saves internal floor space. Outward opening puts the hinge knuckles on the outside of the building, where they can be reached.
If the hinge pins can be driven out, the leaf can be lifted away from its hinge side regardless of how well the lock side is secured.
Three things address it.
Non removable hinge pins, where the pin is retained by a grub screw or a swaged head so it cannot be tapped out.
Hinge bolts, sometimes called dog bolts or security studs. These are fixed pins protruding from the hinge edge of the leaf that engage into holes in the frame when the door closes. Even with the hinges removed entirely, the leaf cannot be lifted out. They are inexpensive and highly effective.
Concealed or security hinges, which place the knuckle inside the rebate where it cannot be reached.
If your French doors open outward, this is worth checking before anything else. It is a straightforward retrofit on most doors and it closes an attack that no amount of locking hardware on the other side prevents.
The primary lock
The active leaf needs a lock that engages at more than one height.
Single point locks engage at handle height only, leaving the top and bottom of a two metre leaf resisting force through the hinges and the astragal alone.
Multi point locks engage at several heights from one handle movement, typically combining hooks or deadbolts with intermediate cams. On a tall leaf this matters considerably, and it also pulls the leaf firmly against its seals along the full stile, which improves weather and draught performance.
The cylinder that drives the lock is a separate replaceable component, and choosing one with anti snap and anti drill features is an inexpensive upgrade. Ensuring the cylinder sits flush rather than protruding costs nothing and matters just as much. We cover this in our guide to keyed locks for aluminium sliding doors, and the same principles apply to hinged doors.
The glass
French doors are mostly glazing, and no locking hardware compensates for a pane that can be broken quietly.
Laminated glass is bonded with a plastic interlayer that holds the glass together under impact. Breaking through takes sustained effort and considerable noise rather than a single strike, which defeats most opportunistic attempts.
It is frequently required anyway. AS 1288 requires Grade A safety glass in doors and in panels adjacent to doors, and laminated satisfies that while also delivering the security and ultraviolet benefits. We cover how it behaves in our article on laminated glass for sliding doors.
A 0.76 millimetre interlayer performs better than the standard 0.38 millimetre for security purposes, and it is worth specifying where the doors are concealed from the street.
Security screens
A security screen door fitted over French doors adds a tested physical barrier in front of the glass.
AS 5039 covers security screen doors and window grilles, setting construction, strength and locking requirements, with AS 5040 covering installation. A screen described as a security screen should comply with these.
Two things worth knowing. AS 5039 governs the screen, not the French door hardware behind it, so a door lock cannot be described as AS 5039 compliant. And a compliant screen is only as good as its installation, which is why AS 5040 exists.
Screens also let you leave the French doors open for ventilation while the opening stays secured, which on a warm Sydney evening is often the real reason people fit them.
Confirm current standard requirements, since they are periodically revised.
Egress
French doors are frequently the main access to a garden or courtyard, which makes them an escape route.
The active leaf must open from inside without a key. A cylinder keyed on both sides defeats a reach through attack but means the door cannot be opened without finding a key, which is a serious hazard in a fire.
Laminated glazing plus an internal thumb turn is the better combination. The glass makes reaching through impractical and the door stays openable.
Flush bolts on the inactive leaf raise no egress concern, since the active leaf opens independently of them.
Putting it together
A properly secured pair of French doors has flush bolts top and bottom on the inactive leaf, an astragal closing the meeting stile, hinge bolts or non removable pins if the doors open outward, a multi point lock on the active leaf with a quality cylinder sitting flush, and laminated glazing.
That combination is comparable to any other external door. Missing any one of them, particularly the inactive leaf bolts or the hinge protection, leaves a specific and exploitable weakness.
Our French doors are manufactured in Villawood with multi point locking, flush bolts and laminated glazing options. If you are still deciding on configuration, our article on types of French doors for exterior use covers the options.
Frequently asked questions
Are French doors less secure than other doors?
Not inherently, but they have two vulnerabilities a single door does not: the meeting stile where the leaves join, and the hinge line if the doors open outward. Addressed properly with flush bolts, an astragal and hinge bolts, they are comparable to any other external door.
What is the most important thing to secure on French doors?
The inactive leaf. If it is not bolted top and bottom into the frame, the lock on the active leaf is engaging into a door that can itself be moved, and the join between the leaves becomes the weak point.
What are hinge bolts and do I need them?
Fixed pins protruding from the hinge edge of the door that engage into holes in the frame when it closes. If your French doors open outward, the hinges are on the outside and hinge bolts prevent the leaf being lifted away even if the hinge pins are removed. They are inexpensive and worth fitting.
Should French doors have laminated glass?
Yes. AS 1288 generally requires Grade A safety glass in doors, and laminated satisfies that while also making forced entry through the glass slow and noisy. Standard toughened glass meets the safety requirement but offers far less security benefit.
Can I add a security screen to French doors?
Yes, and it lets you leave the doors open for ventilation while the opening stays secured. Look for compliance with AS 5039 for the screen and AS 5040 for its installation.
Should my French doors be keyed on both sides?
Generally not, if they are a main exit. A key required from inside is a hazard in a fire. Laminated glazing addresses the reach through concern while keeping the doors openable.
How do I know if my French doors have an astragal?
Look at the meeting stile with the doors closed. If one leaf overlaps the other, there is an astragal. If there is a visible vertical gap running the full height between two flush stiles, there is not, and that gap is a vulnerability.
