Which Doors Are the Safest? A Locksmith's Guide to Door Security

Door security is a product of several factors working together: the material of the door leaf, the strength of the frame and fixings, the quality of the hinges, the specification of any glazing, the design of the letterbox, and finally the lock itself. This guide covers a clear comparison of door types from a trade perspective, an explanation of what standards like PAS 24 and Secured by Design mean in practice, and guidance on where most residential doors fall short — whether you are buying a replacement or assessing what you already have.

Door Material: Solid Timber, Hollow Core, Composite and Steel

Solid timber doors are common in pre-1980 properties across South London. Security depends heavily on the timber species and condition. A solid hardwood door in good condition — oak or sapele — is genuinely difficult to force. Many older timber doors, however, are softwood, and some have been patched or allowed to rot at the bottom rail. A timber door that sounds hollow when knocked is a hollow-core flush door, which provides almost no resistance to a kick-in and should never be used as an external door.

Composite doors are the current standard for new residential installations. They combine a timber or steel subframe with a glass-reinforced plastic (GRP) skin and a foam or solid core. A quality composite door is significantly harder to kick through than most timber alternatives. Reputable manufacturers such as Solidor and Rockdoor produce composite doors with PAS 24 certification, making them a sound choice for insurance compliance as well as security.

Steel-reinforced doors, common in commercial and high-security residential applications, offer the highest physical resistance. For most South London homes, a well-specified composite door set provides adequate protection and is more practical in terms of aesthetics and fitting.

Frame and Hinge Security: The Most Overlooked Element

A strong door in a weak frame is only as secure as its weakest point. The door frame, particularly the strike plate section where the lock bolt engages, must be fixed securely into the structural brickwork or timber stud behind the door lining. Standard strike plates are often supplied with short screws of around 25mm that only reach the softwood lining, not the structure behind it. Replacing these with 75mm or 100mm screws that bite into the stud or masonry significantly increases resistance to a kick-in attack. Research conducted for the Home Office found that the majority of forced-entry burglaries succeed by attacking the frame rather than the lock itself.

Hinges deserve equal attention. A door fitted with standard butt hinges is vulnerable on its hinge side — the door can be levered away from the frame by attacking the gap at the hinge edge. Fitting hinge bolts (also called dog bolts) on the hinge side prevents this. Some composite door systems incorporate continuous security hinges as standard. Anti-jemmy strips, fitted along the lock-side edge of the door frame, prevent a crowbar from being inserted between the door and frame to lever the bolt or latch — these cost under £20 for a set and are straightforward to fit.

What PAS 24 and Secured by Design Actually Mean

PAS 24 is a British Standard published by the British Standards Institution defining enhanced security performance requirements for door sets. A PAS 24 certified door has passed a series of physical attack tests including attempted manipulation, drilling, sustained kicking and levering — tested as a complete unit: door leaf, frame, glazing and lock hardware together.

Secured by Design (SBD) is a police-led accreditation scheme run through the Association of Chief Police Officers. Products approved under SBD must meet or exceed PAS 24 and must be installed in accordance with the manufacturer's specification to retain their certified status. The full approved product database is searchable at securedbydesign.com. Many home insurers either require PAS 24 door sets or offer premium discounts for properties fitted with them.

Glass Panels in Doors: Risks and Solutions

Glass in an external door creates a potential vulnerability. A single pane of plain annealed glass adjacent to a lock or handle can be broken quickly, allowing an intruder to reach through and operate the latch or turn a key left in the lock. Practical solutions: ensure the lock cannot be operated from inside without a key (so breaking the glass does not grant access); and specify laminated glass for door panels rather than toughened (tempered) glass.

Unlike toughened glass, which shatters into small pieces on impact, laminated glass holds together after breaking because of a plastic interlayer bonded between the panes. This significantly increases the time and effort required to create a usable opening. Most PAS 24 certified door panels use laminated glass as a matter of specification. For existing doors with plain glass close to the lock, applying an adhesive security film of at least 100 microns thickness is a practical upgrade that does not change the door's appearance significantly.

Letterbox Security

The letterbox is one of the most exploited vulnerabilities on a front door. The fishing technique — using a hooked rod through the letterbox to retrieve keys left on a hook or hall table — is a documented method used in domestic burglaries. A hand or arm can also be inserted through an oversized letterbox to operate a thumbturn directly.

A letterbox cage or internal letter tidy, fitted on the inside of the door, prevents direct access through the opening. These cost £10 to £25 and take less than 30 minutes to fit. If your current letterbox is larger than 260mm wide, consider replacing it with a smaller, guarded version — this exceeds the standard Secured by Design maximum.

The Lock Itself: Cylinders, Ratings and Vulnerabilities

For euro cylinder locks on uPVC and composite doors, the primary vulnerabilities are:

• Cylinder snapping: the outer section is broken off using a screwdriver, exposing the cam and allowing the lock to be turned open in seconds. Anti-snap cylinders have a sacrificial section that breaks before the cam is reached. Look for cylinders tested to TS007 3-star standard. Ultion, Mul-T-Lock and Yale Superior all produce options at this level.
• Bumping: a bump key is struck into the cylinder to bounce all pins above the shear line. Anti-bump cylinders use modified pin designs that resist this method.
• Picking: anti-pick cylinders use side pins, serrated drivers or false gates to resist manipulation.

For mortice locks on older London properties, BS3621 is the relevant benchmark — a minimum five-lever mechanism required by most UK home insurance policies. If your front door has only a Yale-type nightlatch, check whether a BS3621 mortice is also fitted. A springlatch alone does not satisfy insurer requirements and is far less resistant to attack than a properly engaged deadlock.

Our emergency locksmith service includes on-site cylinder replacement and can supply and fit anti-snap, anti-bump cylinders immediately following a lockout or break-in, ensuring the door is secure before we leave.

Frequently Asked Questions

Is a composite door always more secure than a timber door?

Not automatically. A well-maintained solid hardwood door in a sound frame can match or exceed the security of a poorly specified composite door. The key factors are the core material, the frame condition, the hinge quality, and the lock. A PAS 24 certified composite door set, installed correctly, is currently the most consistent choice available.

How do I know if my cylinder is at risk of snapping?

If the cylinder protrudes more than 3mm beyond the face plate or door handle escutcheon, it presents a larger grip target for a snap attack. A cylinder sitting flush or recessed is harder to lever. Any unrated or single-star cylinder should be replaced with a TS007 3-star anti-snap option as a priority.

What screws should be used in a door strike plate?

The strike plate should be fixed with screws at least 75mm long, ideally 100mm, that reach the structural timber stud or masonry behind the door lining. Standard short screws of 25 to 35mm only hold the plate to the softwood lining, which splits easily under kick-in force.

Does my home insurance require a specific lock standard?

Most UK home insurance policies require at least one BS3621-rated lock on external doors. Some policies also specify that the lock must be engaged for cover to apply when the property is unoccupied. Read your policy schedule carefully and contact your insurer directly if you are uncertain whether your current locks comply.