How to Secure French Doors and Patio Doors

French doors and patio doors are one of the most overlooked weak points in a Manchester home. They sit at the back of the house, out of sight of the street, they're largely made of glass, and many of them are still secured with whatever the builder fitted years ago. That combination is exactly what an opportunist burglar is looking for. If you want to know how to secure French doors so they stop being the easy option, this guide walks through the real weak points and the upgrades that actually make a difference.

Doors are the most common way into a home during a break-in — far more so than windows — and a rear set of French or patio doors gives a burglar room to work unseen. The good news is that almost every weakness can be fixed without replacing the doors, usually in a single visit.

Why French and patio doors attract burglars

A front door faces the street, neighbours and passing cars. A set of French doors onto the garden faces a fence. Once someone is over that fence or through a side gate, they can take their time, and that privacy is the single biggest reason these doors get targeted.

There's more to it than that, though. French doors have two leaves that meet in the middle, which is a join that can be levered. They're mostly glazed, so there's a temptation to smash or pop the glass. And because they're often seen as a secondary exit rather than a main entrance, homeowners tend to spend less on securing them — sometimes the only thing holding the pair shut is the handle and a single cylinder.

We see this across the city, from Victorian terraces in Chorlton with French doors knocked through into a garden, to modern flats in Salford and the city centre with full-height balcony doors. The age of the property changes the details, but the vulnerabilities are remarkably consistent.

Where French doors are actually weak

Before you spend money, it helps to understand what a burglar is looking at. There are five common weak points.

The Euro cylinder

Most uPVC and composite French doors run a multipoint mechanism driven by a Euro cylinder — the same lock barrel you'll find on a back door. If that cylinder is a basic, unrated one, it can be snapped in seconds with simple tools, and the whole door swings open. This is the quickest, quietest way in and it's the first thing to fix. We cover the technique and the defence in more detail in our guide to whether anti-snap locks are worth the cost.

The central meeting stile

Where the two leaves meet, one door (the "slave" leaf) is held shut by bolts top and bottom, and the other (the "master") locks against it. If those bolts are short, worn, or thrown into soft or unreinforced frame material, the pair can be prised apart at the join. Strong bolts engaging reinforced keeps are what stop this.

The hinges

On older or outward-opening French doors, the hinge pins can sit on the outside. Knock the pins out and the door lifts away from the frame on the hinge side, lock or no lock. Even on inward-opening sets, tired hinges allow enough play to lever.

The glass and beading

On units made before internal beading became standard, the strips holding the glass in (the beading) are on the outside. Lever those off and the sealed glass unit can be lifted out cleanly, with very little noise. Newer doors bead from the inside, which removes this route entirely.

The keeps and frame

A lock is only as strong as what it bolts into. Many factory keeps are thin pressed metal screwed into the plastic frame. Upgrade the cylinder all you like — if the keeps tear out under a shoulder barge, the door still opens.

How to secure French doors: the upgrades that matter

You don't need to do everything at once, but the order below gives you the most protection for each pound spent.

Fit a 3-star anti-snap cylinder. This is the single most valuable upgrade. A cylinder carrying the TS007 3-star rating (or a 1-star cylinder paired with 2-star security door furniture) is built to resist snapping, drilling, picking and bumping. Expect roughly £60–£120 fitted per door depending on the cylinder and the measurement of your door — and measuring matters, because a cylinder that sticks out past the handle gives an attacker something to grip. Our article on how to measure a Euro cylinder explains how to get the size right.

Add hinge bolts (dog bolts). These are fixed steel pegs on the hinge edge that locate into the frame when the door is shut, so even if the hinge pins are removed the door stays anchored. They're inexpensive, quick to fit, and they close off the hinge-side weakness completely.

Sort out the shoot bolts and keeps. The bolts at the top and bottom of the slave leaf should throw deep and land in solid, reinforced keeps — not thin metal in soft plastic. Where the original keeps are flimsy, replacing them with reinforced ones makes a real difference to how the door resists levering.

Consider sash jammers. A sash jammer is a simple, low-cost stop fitted to the frame that physically blocks the door from being forced or sliding open. They're not a substitute for a good cylinder and bolts, but as an extra layer — particularly on a door you rarely use — they're cheap insurance.

Upgrade the glass if you can. Where budget allows, laminated glass (the type that holds together when struck, rather than shattering) turns the glazed area from a weak point into a real obstacle. New PAS 24 doors already include at least one laminated pane for exactly this reason. If replacing the glass isn't practical, a quality security film on the inside of the existing pane is a sensible middle ground.

Lock it properly, every time. This costs nothing. On a multipoint door, lifting the handle only engages the latch — the door isn't actually secure until you turn the key and throw the bolts. Plenty of break-ins succeed simply because the door was pulled to but never keyed. Get into the habit, especially with rear doors.

Sliding patio doors are a different job

Older aluminium sliding patio doors have their own classic weakness: the leaf can sometimes be lifted up off its track and out of the frame, even when locked. Anti-lift blocks fitted into the top channel stop this, and a foot-operated patio bolt at the bottom of the frame adds a second locking point that's awkward to reach from outside.

If your sliding doors are decades old and the lock is a single hook in the centre, they're worth a proper look. In many cases a locksmith can add anti-lift devices and an extra bolt far more cheaply than you'd expect, without replacing the whole unit.

What about insurance?

This trips a lot of people up. For wooden French doors, most insurers want a BS3621 five-lever mortice deadlock — the same British Standard they ask for on timber front and back doors. For uPVC and composite French doors, there's usually no mortice lock; instead the insurer is looking for a working multipoint mechanism with a key-operated final lock and, increasingly, an anti-snap cylinder.

The detail varies between policies, so read your wording or ring your insurer before you assume you're covered. If you're unsure what your policy is actually asking for, our explainer on what BS3621 means for your insurance breaks it down in plain terms. The principle is simple: the door has to be locked with a key, not just latched, for a claim to stand.

Manchester homes where this comes up most

In the leafier suburbs — Didsbury, Chorlton, Withington — a lot of period houses have had French doors fitted into a rear reception room or an extension, opening onto a long garden screened from the road. Those are prime candidates for the full set of upgrades, because the privacy that makes them lovely to live with is the same privacy a burglar relies on. If you're in one of these areas, our locksmiths cover Didsbury and the surrounding suburbs daily and can assess a rear door on the spot.

In Salford, the city centre and around Old Trafford, the pattern is different: newer flats and balcony doors where the mechanism and cylinder are sound but rarely upgraded from the developer's basic spec. Here the win is usually a cylinder swap and a habit change — always keying the door.

When to call a locksmith

If your French or patio doors are stiff, dropped, no longer lock without a fight, or still wearing the cylinder the builder fitted, it's worth getting them looked at before they fail or get tested by someone you'd rather keep out. A locksmith can measure and fit an anti-snap cylinder, add hinge bolts, replace worn keeps and adjust a dropped door — and if the multipoint mechanism itself has failed, our uPVC door repair service replaces the gearbox rather than the whole door.

If you've already had an attempted break-in, don't wait. We can secure the doors the same day and fit British Standard and anti-snap hardware as part of our burglary repair work, with a written report for your insurer.

The bottom line

French and patio doors don't have to be your weak link. The fixes are well understood and most cost far less than people imagine: a rated cylinder, hinge bolts, solid bolts into reinforced keeps, and the discipline to lock the door with the key every time. Get those right and a door that used to be the soft option becomes one of the harder ways into your home.

If you'd like your French or patio doors assessed and upgraded, get in touch for a no-obligation quote. We'll tell you exactly what each door needs — and what it doesn't — before any work starts.