Patio doors look beautiful and flood a room with light. They also have some security characteristics that make a straightforward break-in surprisingly easy — and most homeowners don’t know about them until something goes wrong. A sliding patio door can often be lifted off its track in seconds. A bi-fold door with a worn multi-point lock mechanism can be pushed open with steady pressure. Even modern UPVC units vary enormously in their resistance to attack. The good news is that every vulnerability covered in this guide has a practical, affordable fix — and your insurer is likely to ask about most of them.
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Key Takeaways
- Sliding patio doors can be lifted off their tracks without forcing the lock — anti-lift pins or security blocks cost under £30 and eliminate this vulnerability.
- Bi-fold doors’ security depends almost entirely on the quality of their multi-point locking hardware — if yours are over 10 years old, have the locks serviced or replaced.
- All patio doors should have alarm contacts fitted — a magnetic contact triggered when the door opens is cheap, discreet and one of the most reliable alarm triggers.
- Building Regulations Part Q sets minimum security standards for new patio doors — but older installations may fall well short of these standards.
- What your insurer expects: a British Standard (PAS 24 or BS 7950) certified door, functioning multi-point locks, and ideally an alarm. Check your policy wording carefully.
- For wider home security, see our guides to home alarm systems and window and door security.
Sliding Patio Door Vulnerabilities
Traditional sliding patio doors — the type with one fixed panel and one sliding panel running in a top and bottom track — have two classic vulnerabilities that have been exploited by burglars for decades. The first is the lift-out attack: most sliding doors have a small amount of vertical play in their tracks, allowing the panel to be lifted upward and then swung outward at the bottom, bypassing the lock entirely. The door literally comes off the track — no damage to the lock, no glass breaking, no noise. The second is the basic lock attack: many older sliding doors use a simple hook or lever lock that provides minimal resistance to a jemmy or sustained pressure.
Neither vulnerability is present in a well-specified modern door — PAS 24 tested UPVC sliding doors are specifically tested for lift-out resistance and lock strength. But if your sliding patio door is more than ten years old, or was a budget installation, assume it’s vulnerable until you’ve checked. The Met Police crime prevention guidance specifically identifies patio doors as a priority for secondary security measures.
Bi-Fold Door Vulnerabilities
Bi-fold doors — those wide, accordion-style doors popular in modern extensions — present a different set of security challenges. The folding mechanism means there are multiple panel-to-panel and panel-to-frame joints, each of which needs to be secured by the locking system. A well-designed bi-fold door with quality hardware from Schuco, Smart Systems or Origin is a genuinely secure installation. A budget bi-fold, or one with worn or misaligned multi-point locks, can be forced with surprisingly little effort — the frame is often the weakest point, not the glass.
Common vulnerabilities: worn or misaligned espagnolette bolts that don’t engage their keep plates fully; missing or damaged top and bottom bolts on the inactive leaf; a master door (the one with the handle) whose multi-point lock isn’t fully lifting into engaged position when turned. Have your bi-fold locks adjusted and lubricated annually — most DG companies charge £50–£100 for a service visit and it can make a significant difference to performance and security. If yours are over ten years old and showing signs of wear, replacing the lock hardware (typically £200–£400 including fitting) is a proportionate investment.
Anti-Lift Pins: The Simplest Sliding Door Fix
Anti-lift pins are the most cost-effective single upgrade for any sliding patio door. They’re small bolts or pins screwed into the top channel of the door frame above the sliding panel, reducing the vertical clearance to zero — the panel physically cannot be lifted out of the track with them in place. Fitting typically involves drilling two small holes into the door frame (which can be filled if you remove them later — suitable for renters with landlord permission) and takes about 20 minutes. The Surefire sliding door anti-lift pin set (around £14.99) and the ERA sliding door security pins (£18.99 for four) are both widely available from Screwfix and Toolstation. Fit two per door — one near each end of the panel.
An alternative approach is a door security bar — a length of adjustable steel bar or timber cut to length and placed in the bottom track. This prevents the door from being slid open even if the lock is defeated, though it must be removed manually each time you use the door. The Master Lock 265D adjustable security bar (£29.99) handles patio doors as well as outward-opening doors and windows. It’s a blunt but effective solution, particularly for overnight security or when away on holiday.
Lock Upgrades for Sliding Doors
If your sliding door’s existing lock is a basic hook or hook-bolt type, consider adding a secondary lock. The ERA Fortress sliding door patio lock (£34.99) fits onto the inside of the door frame and provides a substantial drop bolt that cannot be defeated without serious force. The Chubb Battleship sliding door lock and the Fuhr sliding door lock are also worth considering — both add a bolt-style deadlock that operates independently of the primary hook mechanism. For aluminium sliding doors, ensure any secondary lock is compatible with the door frame profile (sizes vary — take measurements before buying).
For doors that are still fit for purpose but have an ageing primary lock, a lock upgrade from a UPVC door and window specialist (often £80–£150 fitted) can bring performance significantly closer to current PAS 24 standards without replacing the entire door. This is usually the right answer for 10–15-year-old doors that are otherwise structurally sound. For our wider guidance on door lock standards and specifications, see our detailed door locks guide.
Alarm Contacts and Sensors
Fitting an alarm contact to a patio door is cheap, unobtrusive, and one of the most reliable alarm triggers in any system. A standard magnetic door contact consists of two small components — a magnet and a sensor — fixed either side of the door and frame. When the door opens, the magnetic field breaks and the alarm triggers. On a sliding door, contacts sit at the end of the sliding panel and the fixed frame; on a bi-fold, they go on the master door leaf and its jamb. Wireless contacts for DIY alarms (compatible with Ring Alarm, Yale Smart Home, Ajax, etc.) typically cost £15–£25 each from the manufacturer or from Screwfix. Wired contacts for professionally installed alarms cost roughly the same in hardware plus labour to install.
A shock sensor is a useful addition: it detects the vibration of glass being struck or a frame being forced, triggering the alarm before the door actually opens. The Ajax DoorProtect Plus (£59.99) combines magnetic contact with shock sensing in a single unit — particularly useful for bi-fold doors where a forced entry might not initially open the door cleanly. Pair with a PIR covering the area immediately inside the door as a belt-and-braces approach. For more on alarm system options, see our NSI-approved alarms guide.
Reinforcing Frames
The lock is only as good as the frame it locks into. UPVC frames can crack or deform under sustained attack; aluminium frames are stronger but can be levered at the join between frame sections. A few practical measures significantly improve frame resistance. Security hinge bolts on the hinge side of any door — including the active door panel of a bi-fold — prevent the door being forced off its hinges. Anti-crowbar plates (around £15–£30) fit behind the lock keep plate and spread the load of any levering attack across a wider area of the frame. For aluminium bi-fold and sliding doors with long unsupported sill tracks, additional steel bolting into the sill can be specified during installation on new builds — something worth requesting explicitly from your installer.
What Your Insurer Expects
Home insurers are increasingly specific about patio door requirements, particularly as bi-fold doors have become common in mid-to-high value properties. The following table summarises what most standard and premium home insurance policies expect:
| Security measure | Standard home insurance | Premium/high value home insurance |
|---|---|---|
| Multi-point locking on patio/bi-fold doors | Usually required | Required — often specified as PAS 24 certified |
| Anti-lift measures on sliding doors | Recommended, not always required | Often required |
| PAS 24 or BS 7950 door certification | Recommended for new installations | Often required for new installs |
| Alarm contact on each patio/bi-fold door | If alarm is fitted, this is usually required | Required if any alarm discount applied |
| Alarm system (monitored) | Discount offered, usually not required | Often required for full cover |
| Key-operated secondary lock or security bar | Not usually required | May be required on isolated or accessible doors |
Always read the physical security conditions section of your policy carefully. Many insurers include a “policy conditions” clause that voids cover if you fail to lock or secure a door through which entry was gained — in the event of a claim, an unsecured patio door can be used to deny payout. For broader guidance on what UK home insurers require from security hardware, the Which? home insurance and home security guide is an authoritative starting point. The Building Regulations Approved Document Q sets the minimum security standard for doors in new dwellings — useful context even if you’re upgrading an existing door.
Product Recommendations Summary
| Product | Purpose | Approx. Price |
|---|---|---|
| ERA sliding door anti-lift pins (pack of 4) | Prevent sliding panel lift-out | £18.99 |
| Master Lock 265D adjustable security bar | Secondary track lock for sliding doors | £29.99 |
| ERA Fortress sliding patio lock | Secondary deadbolt for sliding doors | £34.99 |
| Ajax DoorProtect Plus | Magnetic contact + shock sensor | £59.99 |
| Yale door alarm magnetic contact (wired) | Basic magnetic door contact for alarm system | £14.99 |
| Anti-crowbar strike plate reinforcer | Frame reinforcement behind lock keep | £18–£30 |
| Multi-point lock service (specialist) | Realign, lubricate and adjust existing locks | £50–£100 |
| Multi-point lock replacement (bi-fold, fitted) | Replace worn locking mechanism | £200–£400 |
Final Thoughts
Patio doors are one of those areas where the security shortfall between how they look and how they perform can be quite stark. The vulnerabilities are real and well-known to opportunist burglars. But every one of them is fixable — and the total cost to comprehensively secure a sliding patio door with anti-lift pins, a secondary lock, an alarm contact and a shock sensor is under £150. That’s a proportionate investment for any door that covers a garden, patio or ground-floor access point. Don’t overlook the basics: lock the door every time you leave the room, even during the day. The majority of break-ins are opportunist — a locked door with visible security measures is usually enough to send someone elsewhere.