What are alarm grades 1 to 4, and which do I need?

The grades in BS EN 50131 describe the level of intruder a system is designed to resist, from Grade 1 for low risk to Grade 4 for high-value or high-risk premises. Most UK homes are specified at Grade 2, and most commercial premises at Grade 2 or Grade 3.

Grade 1 assumes an intruder with little knowledge and no tools, and is rarely specified for anything that matters. Grade 2 assumes an intruder with some knowledge and basic tools — the normal domestic specification. Grade 3 assumes an intruder who understands alarm systems and carries a range of tools, and is typical for commercial premises and higher-value homes. Grade 4 covers high-risk sites where the intruder is expected to plan and to bring specialist equipment.

The grade drives real requirements, not just a label: detector types and tamper protection, how much standby battery is needed, how quickly a lost signalling path must be noticed, and how the system must behave when part of it fails.

Grade is chosen from a risk assessment of your property and contents. Your insurer may specify a minimum, and if so that specification wins — ask them before you buy rather than after a claim.

Higher is not automatically better for you. A Grade 3 system on a normal house costs more, and its stricter tamper and fault requirements can mean more nuisance faults, without a corresponding gain.