Patio Doors and French Doors: The Security Upgrades That Actually Work

Patio doors and French doors are one of the most common weak points I deal with across Coventry. They look great, they let light in, and they give you easy access to the garden. They also give burglars easy access to your house if they are not properly secured.

The problem is not that these doors are inherently insecure — modern ones with good multipoint locks are decent. The problem is that many homes in Coventry have older patio or French doors with basic locks, worn mechanisms, or design vulnerabilities that make them relatively easy to defeat.

Here is what I see on the job, the specific weaknesses to look for, and the upgrades that actually make a difference.

Patio Door Vulnerabilities

Lifting Off Tracks

Older sliding patio doors can often be lifted straight up and off their bottom track. The rollers sit in a channel, and if there is enough clearance at the top, the entire door can be raised and pulled inward. I have demonstrated this to shocked homeowners more times than I can count — it takes about 5 seconds with no tools.

The fix: Anti-lift devices. These are pins, blocks, or strips that sit in the top track and prevent the door being raised high enough to clear the bottom rail. Cost: about £15-£25 fitted. It is one of the cheapest and most effective security upgrades you can make.

Weak Standard Locks

Many patio doors come with a simple latch lock — a hook or claw that engages when you push the handle down. These are designed to keep the door closed, not to resist forced entry. A firm tug or a screwdriver levered into the gap can defeat them.

The fix: Fit a dedicated patio door lock. These are key-operated locks that bolt through the frame, independent of the main latch. Brands like Yale and ERA make purpose-designed patio door locks. Cost: about £30-£50 fitted.

Track Manipulation

On some sliding doors, the track can be bent or deformed with a pry bar, creating enough room to slide the door past the lock engagement point. Older aluminium tracks are particularly vulnerable.

The fix: A foot bolt or drop bolt at the base of the sliding panel adds an anchor point independent of the track. Security bars that sit in the track behind the sliding panel are another option — the door simply cannot be opened far enough to allow entry. Cost: £20-£40.

Glass Panel Attacks

Most patio doors have large single or double-glazed panels. Standard float glass breaks easily and relatively quietly (a spark plug fragment can silently shatter toughened glass, and standard float glass can be broken with a simple tool wrapped in a cloth).

The fix: If you are replacing the glass for any reason, specify laminated glass. Unlike toughened glass (which shatters into small pieces), laminated glass holds together when broken — the interlayer keeps the fragments in place, making it much harder to create an opening large enough to climb through. For existing glass, security film can be applied to the inside surface. It is not as good as laminated glass but significantly better than nothing. Laminated glass replacement starts from around £150-£250 per panel depending on size.

French Door Vulnerabilities

The Passive Leaf Problem

French doors have two doors, but typically only one is used daily (the active leaf). The other (the passive leaf) is held in place by flush bolts or shoot bolts at the top and bottom. If these bolts are missing, broken, or not engaged, a burglar only needs to force one bolt point instead of dealing with the full multipoint lock.

The fix: Ensure the passive leaf has working flush bolts or rack bolts at the top and bottom. Key-operated rack bolts are more secure than simple flush bolts because they cannot be vibrated open. Cost: £15-£25 per bolt fitted, so about £30-£50 for top and bottom.

Multipoint Lock Failure

French doors typically have a multipoint locking system operated by lifting the handle. Over time, the hooks, bolts, and compression points can wear, misalign, or break. If the handle lifts but feels loose or does not click into a positive lock at multiple points, the mechanism needs attention.

The fix: The multipoint lock gearbox or individual locking points can be replaced without changing the door. This is a specialist job and costs from £95-£175 depending on the mechanism. Much cheaper than a new set of French doors. Check our [uPVC lock repair service](/services/upvc-lock-repair) for more details.

Hinge Vulnerability

If French doors open outward, the hinges are exposed on the outside. Standard hinges can be unbolted, allowing the door to be removed entirely even if the lock is engaged.

The fix: Hinge bolts (also called dog bolts) — fixed pins on the hinge side of the door that engage with holes in the frame when the door is closed. Even if someone removes the hinge pins, the door cannot be pulled away from the frame. Cost: about £10-£15 per pair fitted.

Cylinder Attacks

If your French doors have a euro cylinder (the standard keyhole found on uPVC and composite doors), it is vulnerable to the same [lock snapping attacks](/blog/what-is-lock-snapping) as any front door with a standard cylinder. An anti-snap cylinder is essential.

The fix: Replace with an anti-snap, anti-bump, anti-pick cylinder. I recommend Ultion, ABS, or Yale Platinum. Cost: from £90-£120 fitted. See my [anti-snap lock comparison](/blog/anti-snap-locks-compared) for a detailed breakdown.

Glazing Upgrades

For both patio and French doors, the glass is a potential entry point. Here are the options from least to most expensive:

Security Film (from £50 per panel)

A thick polyester film applied to the inside of the glass. It holds the glass together when smashed, making it much harder to create an entry hole. Not as effective as laminated glass but a good retrofit option.

Laminated Glass (from £150-£250 per panel)

The gold standard. Two layers of glass bonded with a tough plastic interlayer. When struck, the glass cracks but stays in the frame. It takes sustained, noisy effort to break through — exactly the kind of time and noise a burglar wants to avoid. If you are replacing glass for any reason, always specify laminated.

Toughened Glass

Often assumed to be "security glass," but it is not. Toughened glass is stronger than float glass, but when it breaks it shatters completely into small pieces, creating an immediate opening. It is required by building regulations in doors for safety reasons (the pieces are not sharp), but it provides minimal security against forced entry.

Specific Upgrades: Summary and Costs

Here is a quick reference for what each upgrade costs, supplied and fitted, in the Coventry area:

|---------|-------------|

For a typical set of patio or French doors, a comprehensive security upgrade — anti-lift, auxiliary lock, rack bolts, and an anti-snap cylinder — costs in the region of £150-£250 total. That is a significant improvement for a modest outlay.

What I Recommend for Coventry Homes

Most of the patio and French doors I see in Coventry fall into two categories:

1. Doors from the 1990s-2000s — These typically have basic locks, no anti-lift devices, and standard euro cylinders. They need the full set of upgrades listed above. The doors themselves are usually fine structurally, so replacing them is unnecessary.

2. Doors from 2010 onward — These usually have multipoint locks and better glass, but may still lack anti-lift devices and often have standard (snappable) euro cylinders. Upgrading the cylinder and adding anti-lift devices is usually sufficient.

If you are not sure which category yours falls into, or you want me to check the current security of your patio or French doors, call me on 07735 336175. I cover all areas of Coventry and Warwickshire, and I can usually give you an assessment and fit the upgrades in a single visit.

See the full [home security checklist](/blog/home-security-checklist-2026) for everything else to check while you are securing your home, or visit the [prices page](/prices) for our complete list of services and costs.