Window and door security is the single most impactful area of home protection for UK homeowners. According to Home Office statistics, around two-thirds of domestic burglaries involve entry through a door or window — not through walls, roofs, or garages. Understanding which weak points burglars actually target, and what security measures genuinely address them, is far more useful than spending money on visible deterrents that do not address the entry point. This guide covers the practical upgrades that make a difference, with honest costs.
The Home Office crime outcomes data and Metropolitan Police research consistently show the same pattern of entry methods:
The majority of break-ins are opportunistic. The Metropolitan Police residential burglary guidance notes that most burglars spend fewer than 60 seconds attempting entry before moving on. This means that resistance — buying time — is the primary function of physical security measures. You do not need to make your home impenetrable; you need to make it more effort than the house next door.
PAS 24 is the key British Standard for enhanced security performance of windows and doors. It is tested by applying a defined set of manual attacks — drilling, levering, kicking, and manipulation — and measuring resistance time. Windows and doors that meet PAS 24 are significantly harder to force quickly. They are required by Building Regulations Approved Document Q for new dwellings in England.
If you are replacing windows or external doors in an existing property, specifying PAS 24 certified products is one of the highest-value security upgrades you can make. The cost premium over standard products is typically 10–20%, and the security benefit is substantial. For the full specification, see the GOV.UK Approved Document Q guidance.
Beyond PAS 24, the Secured by Design scheme (the official police security initiative) sets a higher bar — SBD-certified products have passed additional testing and are the standard recommended by Which? home security guidance and police architectural liaison officers for higher-risk properties.
Lock snapping is the most common forced entry method for UPVC doors in the UK. The attacker snaps the euro cylinder (the barrel of the lock) using leverage, which exposes the mechanism and allows the door to be opened in seconds. A huge proportion of UPVC doors installed before 2015 are vulnerable to this attack.
The solution is straightforward: replace the euro cylinder with an anti-snap cylinder. Look for cylinders that carry the TS007 3-star rating or SS312 Diamond grade. These are specifically tested against snapping attacks and offer dramatically better resistance. Fitting takes 20–30 minutes and costs £30–£80 for the cylinder, or around £100–£150 with a locksmith fitting it.
Even a good lock is only as strong as the frame it is mounted in. Kicking or shouldering a door transmits force to the frame, and many standard door frames — particularly on older timber properties — will split at the strike plate under a determined attack. Reinforcement options include:
Multipoint locks engage at three or more points along the door edge — typically top, middle, and bottom — rather than the single bolt of a traditional lock. This distributes resistance across the full height of the door and makes frame failure much harder to achieve by brute force. Most modern UPVC and composite doors already have multipoint locks fitted, but they are only effective when fully engaged. Many homeowners pull the door shut and turn the handle without lifting and turning the key — this leaves only the latch engaged. Always lock the door fully with the key when you leave.
A standard letterbox is a hand-sized gap in your front door. Thieves use letterbox fishing to hook keys left visible on a hallway table, and in some cases use the gap to manipulate the door handle. Solutions include letterbox cages (fitted inside, prevent any reach through), letter plates that restrict opening angle, and simply keeping keys out of sight of the letterbox. A basic letterbox cage costs £10–£25 and fits in minutes.
Many older casement and sash windows have only a simple catch — no real lock. Adding key-operated window locks is a low-cost, high-impact upgrade. Friction stays (the arm that holds a casement window open) can be replaced with lockable versions that also prevent the window being pushed fully open from outside. For sash windows, sash stops and dual screws prevent the sashes being lifted or pushed sideways.
Lock a window on the first floor as well as the ground floor. First-floor windows with accessible drainpipes or flat roofs are regularly used as secondary entry points.
Window restrictors limit how far a window can open, typically to 100mm. They are primarily a child safety measure but provide a useful security benefit — a window held to 100mm opening cannot be used as an entry point by an adult. Key-operated restrictors allow full opening when needed while providing security when the window is on the latch. Cost is £10–£30 per window for quality restrictors.
Standard double-glazing breaks under a sharp impact, and while breaking glass creates noise, a determined burglar can clear a frame quickly. Security glazing options include:
Sliding patio doors and French doors are a common weak point. Sliding patio doors can often be lifted off their tracks, bypassing the lock entirely. Anti-lift devices — simple bolts screwed into the frame above the top of the door — prevent this. Always use a secondary security bar in the floor track as well; they cost around £15 and cannot be defeated from outside.
French doors often have a single multipoint lock but two door panels. The passive panel (the one without the primary lock) relies on shoot bolts at top and bottom — make sure these are always engaged when the doors are locked. Adding a surface-mounted security bar or chain to French doors provides useful backup security, particularly for older installations where the main lock is not of modern quality.
| Upgrade | DIY cost | Fitted cost | Impact |
|---|---|---|---|
| Anti-snap euro cylinder (per lock) | £30–£60 | £90–£150 | Very high — addresses most common forced entry |
| Door frame reinforcement kit | £40–£80 | £100–£200 | High — prevents kick-in |
| Letterbox cage | £10–£25 | £30–£60 | Medium — stops letterbox fishing |
| Window locks (per window) | £10–£25 | £30–£60 | High — prevents opportunistic entry |
| Window restrictor (per window) | £10–£30 | £25–£50 | Medium — prevents access through open windows |
| Security window film (per window) | £15–£30 | £40–£80 | Medium — slows glazing attack |
| Patio door anti-lift and bar | £20–£45 | £50–£90 | High for sliding doors |
| PAS 24 door replacement | N/A | £800–£2,500 | Very high — comprehensive upgrade |
Physical door and window security works best as part of a layered approach. A well-secured door paired with visible external lighting and a burglar alarm creates genuine deterrence — each layer adds time or risk for an intruder. Our guide to the best home alarm systems in the UK covers the alarm options available, including systems that can trigger both locally and to a monitoring centre. For external deterrence, motion sensor lights are a cost-effective first layer that works alongside physical security measures.
If you are planning a broader security upgrade, our complete guide to securing your home gives a systematic framework for assessing and addressing vulnerabilities across the whole property.
Many UK home insurers specify minimum security requirements for contents or buildings cover — typically a five-lever mortise deadlock to BS3621 on external doors and key-operated window locks on accessible windows. Failing to meet these requirements can invalidate a claim. Check your policy schedule carefully, particularly if your home has older locks or single-glazed windows. Upgrading to PAS 24 doors and windows may also attract a discount from some insurers — worth asking about when you renew. The Which? guidance on home insurance security requirements is a useful reference for what insurers commonly require.
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