A commercial intruder alarm should be specified to the security grade your insurer requires (usually Grade 2 or Grade 3 under EN 50131), installed by an SSAIB or NSI approved company, and connected to a 24/7 monitoring centre with dual-path signalling. Bells-only systems satisfy almost nobody: without monitoring there is no response, and without certification many insurance policies are quietly invalid.
Keeping your commercial premises secure is about more than protecting assets – it's about protecting people, data, and business continuity. Here is what actually matters when you specify a system, in plain English.
Security grades: what Grade 2 and Grade 3 actually mean
European standard EN 50131 grades intruder alarm systems by the sophistication of attack they are designed to resist. Grade 2 assumes intruders with basic tools and some knowledge — appropriate for most offices, retail units and light commercial premises. Grade 3 assumes a planned attack with technical knowledge and equipment, and is commonly required by insurers for warehouses with valuable stock, pharmacies, jewellers and any premises with an attractive target. Your insurance schedule normally states the grade required; if it doesn't, ask before you buy, not after a claim.
Monitored or bells-only?
A bells-only system makes a noise and hopes someone cares. On an industrial estate at 2am, nobody does. A monitored system signals to an alarm receiving centre, where operators confirm the activation — by sensor sequence, audio or live video — and then act: keyholders called, response service dispatched, or police notified. Monitoring typically costs from around £1 a day, which is why we fit very few bells-only systems for business customers.
Police response and URNs
Police forces only guarantee response to confirmed activations from certified, monitored systems holding a Unique Reference Number (URN). URNs are only available through approved installers — one of the practical reasons SSAIB certification matters. Repeated false alarms downgrade and eventually remove police response, which is why modern systems use sequential confirmation and dual-technology detectors to filter out the wind, the wildlife and the delivery driver.
What your insurer expects
- A system installed and maintained by an SSAIB or NSI approved company
- The grade specified in your policy schedule (commonly Grade 2 or 3)
- A current certificate of conformity, renewed through annual maintenance
- Monitored signalling where the policy demands it — often dual-path
- Keyholder arrangements that actually work at 3am
The most expensive intruder alarm is the one that fails an insurance condition you didn't know existed. We see it after the event: a claim queried because the system was uncertified, unmaintained, or the wrong grade for the cover.
Design beats hardware
The difference between a system that works and one that annoys everyone is design: detector choice matched to each space, entry routes that give staff time to unset without false alarms, zoning that lets you part-set the building for out-of-hours working, and app control with a proper audit trail of who set and unset, and when. That is survey work, not catalogue work.
What it costs
For a typical small commercial site, a professionally installed Grade 2 monitored system starts from roughly £1,400–£2,600 installed, with monitoring from around £349 a year. Larger or higher-grade systems scale with detector count and signalling requirements — our pricing guide breaks the numbers down honestly, or use the pricing calculator for an instant range for your site.