Home Security for London Extensions: Alarms, Smart Locks, CCTV, and Insurance

A home extension changes the geometry of the existing alarm system, and the existing system must be reviewed and updated as part of the extension project. Key principles for alarm system design in an extended property: Zone coverage of new spaces: the extension creates new interior spaces (open-plan kitchen-dining, new ground-floor rooms, new loft rooms) that must be covered by the alarm system. Each new space requires at least one passive infrared (PIR) motion detector. Larger open-plan spaces may require two PIR detectors positioned to eliminate shadow zones (dead spots not covered by the PIR's cone of detection). New access point protection: every new external door (bifold doors, utility room back door, roof terrace door) must have a door contact switch that triggers the alarm if the door is opened while the system is set. Casement windows in extension ground-floor or easily accessible rooms should have window contact switches. Roof windows in loft conversions should have window contacts if they are within reach of a flat roof or fire escape ladder. Grade 2 BS EN 50131 alarm system: for a London property with a significant extension (over £100,000 rebuild value), a Grade 2 alarm system compliant with BS EN 50131 and installed by an NSI or SSAIB approved company is recommended. NSI or SSAIB approved installation is typically required by home insurers for premium cover and is the standard required by most police Alarm Receiving Centre (ARC) monitoring agreements in London. Monitored alarm: a Grade 2 system with 24/7 ARC monitoring, verified alarm response (where the ARC attempts phone or visual verification before contacting police), and a keyholder service is the appropriate specification for a London extended property. Monthly monitoring cost: £20-£50 depending on the monitoring company and response level. Smart alarm integration: smart alarm systems (Texecom Connect, Bosch, Ajax, Orisec) that allow the homeowner to arm, disarm, and view zone history from a smartphone app, receive push notification alerts for triggered zones, and integrate with smart home systems are well-suited to London extended properties where the homeowner wants remote monitoring and control. Smart alarm costs: installation of a new Grade 2 smart alarm system with full coverage of an extended property (4-6 bedroom, 2-storey rear extension, loft conversion) is typically £1,500-£4,000 installed, depending on the number of sensors and the control panel specification.

CCTV cameras protect the extended property and can satisfy home insurer security requirements. The key considerations for CCTV on a London extended property: Camera placement for an extended property: the extension creates new rear elevation, new side access, and in the case of a loft conversion, new roof-level views. A well-designed CCTV system for an extended London property typically includes: front elevation (covering the front door, driveway, and street approach); rear elevation (covering the rear garden, the extension's bifold/sliding doors, and the side access gate); side elevation or side gate (covering the side return passage if there is one); internal cameras are a personal choice — some homeowners choose internal cameras for the garage or utility room; a camera covering the rear lane or alley is worth considering if the property backs onto a shared alley. Camera specification: IP cameras (PoE or Wi-Fi) with 1080p or 4K resolution, night vision (IR or colour night vision), weatherproof rating IP66 or IP67 for external use, wide-angle lens to maximise coverage per camera. Cloud storage or local NVR: cloud storage (subscription-based, £5-£20/month) provides off-site backup of recordings. A local NVR (Network Video Recorder) with an HDD provides local storage without a subscription but is on-site — if the NVR is stolen or destroyed in a fire, the recordings are lost. A combination of local NVR and cloud storage is the most secure arrangement. Planning consent for CCTV: domestic CCTV cameras on a private property do not require planning permission under permitted development rights — installing a camera on the wall or soffit of a dwelling-house is permitted development (Class C, Part 1, Schedule 2, Town and Country Planning (General Permitted Development) Order 2015), provided the camera does not cover a neighbour's land or public space further than necessary for security purposes. In a conservation area, additional restrictions may apply (planning permission may be required for cameras visible from the street). The ICO CCTV Code of Practice: domestic CCTV that captures images of public spaces (the public pavement or road) or neighbours' private land is subject to the UK GDPR and the ICO's CCTV Code of Practice. Cameras should be positioned, where possible, to capture images of the homeowner's own property only. If a camera does capture a public space, the homeowner should register with the ICO (nominal annual fee) and display a CCTV notice. Failure to comply is a civil matter — council enforcement of this is relatively uncommon for domestic systems — but good practice is to minimise capture of non-owned spaces. CCTV installation cost: a 4-camera IP PoE system (2 external, installed) with an NVR and 1TB HDD is typically £600-£1,200 installed by a security contractor. A 6-8 camera system for a larger extended property: £1,000-£2,500 installed.

Smart locks are increasingly common in London extended properties where the extension creates additional external doors (rear door to garden, side gate, utility room access). Key points for smart locks on London extensions: Multi-point locking — all external doors on a London property should have multi-point locking mechanisms that engage at least 3 points (top, bottom, and latch) when the door is locked. This applies to the extension's bifold doors, patio doors, and any other external door. Single-point locking (only at the handle) is inadequate for security. British Standard locks — BS 3621 night latch or deadlock (for hinged doors) is the standard required by most home insurers. Mortice deadlocks and cylinder deadlocks to BS 3621 are specified by the police's Secured by Design scheme. Smart cylinder locks — smart cylinder locks (August, Yale Conexis, Ultion Smart, Abloy, EVVA) replace the existing cylinder on a standard mortice lock and add keypad, NFC, or app-based unlocking. This allows keyless access for tradespeople during the build (time-limited codes), guest access, and remote locking and unlocking via the homeowner's smartphone. Bifold and sliding door security — the most common weakness in London extension security is the bifold or sliding door — the handles and multi-point locking must be tested in the installed position (some large bifold sets are difficult to lock fully when the floor or frame is not perfectly aligned). The extension contractor must carry out a final door alignment and locking test before handover. Door specification — for security, the door specification should include: multi-point locking; BS PAS 24 door set or SBD-compliant door set; secured by design glazing if bifold or patio doors have accessible glass panes; anti-lift pins or shootbolts at the top and bottom of the bifold/patio door to prevent the door from being lifted off the track. Smart access cost: a smart cylinder lock (high security, Yale or Ultion) is typically £150-£350 including installation. A video doorbell (Ring, Nest, Arlo) at the front door is £150-£350 including installation.

A home extension has direct implications for home insurance: notifying the insurer, rebuilding cost update, and policy review. Notify the insurer before construction starts: as noted in the pre-start checklist, notification to the home insurer before construction starts is essential. Standard buildings and contents insurance policies exclude cover during significant structural works, or require a specific endorsement for the construction period. The insurer may require: confirmation of the contractor's public liability insurance; a site risk assessment; an increased premium during the construction period; or a site-specific construction insurance policy (if the main project contract uses a JCT form, the contractor normally takes out Joint Contract Works insurance). After construction — update the rebuilding cost: the extension increases the total rebuilt cost of the property (the sum insured for buildings insurance). The rebuilding cost is not the market value of the property — it is the cost of demolishing the existing structure and rebuilding it from scratch to the same specification. For a 20-25m² rear extension, the increase in rebuilding cost is typically £75,000-£120,000 for a London quality extension with full structural works and fit-out. Failing to update the sum insured results in under-insurance, which means the insurer pays only a proportion of any claim (the proportion representing the insured amount divided by the actual rebuilding cost). After construction — security specification: many London home insurers require specific security standards for cover, including: minimum lock specification (BS 3621 deadlocks on external doors); smoke alarms on every floor; in some cases a monitored alarm system (NSI or SSAIB approved) for full cover or for cover of high-value contents. After an extension, the property's total floor area increases, and the insurer may reassess the property's risk category. A new security assessment and security upgrade to the extension's external doors and windows is worth carrying out at extension completion to ensure ongoing insurer requirements are met.