Most people meet safe grades as a row of Roman numerals on a datasheet and assume they work like stars in a hotel guide — more is better, pick what you can afford. They are stricter than that, and knowing what the number actually measures changes which safe you buy.
What the grade measures
EN 1143-1 grades a safe by tested resistance to attack, expressed in resistance units. A laboratory attacks the body and the door with defined tool sets and records the effort needed for two separate outcomes: partial access — an opening large enough to get valuables out — and complete access. Both figures have to be met before a grade is awarded.
So a grade is a measurement, not an opinion, and it is comparable across manufacturers. Grade IV from one factory and Grade IV from another survived the same test.
What a grade does not tell you is how long a safe will resist a specific attack in your building. Resistance units are a laboratory currency. They are meaningful for comparison and for insurance, and they are not minutes.
The letters after the number
Three suffixes appear across our range, and each answers a different problem:
- LW — a light-weight body that reaches the same graded resistance at a fraction of the weight. This is what makes an upper-floor installation possible without a structural survey of the slab. LW bodies carry no fire rating.
- CD — Core Diamond, tested against diamond-tipped core drilling. Specified where an attacker would have hours and mains power rather than minutes.
- EX — tested resistance to explosives, at the top of the range.
A Grade IV LW and a Grade IV standard body are equally certified. They differ in what else they survive and in what the floor has to carry.
Deposit systems are a different standard
If money goes in without the door opening, EN 1143-1 is the wrong test. EN 1143-2 covers deposit systems: it grades the burglary resistance of the body and, separately, resistance to fishing and manipulation through the deposit opening — the attack that does not touch the door at all.
Ask which standard is on the certificate before you compare two units. A deposit safe certified to EN 1143-2 and a safe certified to EN 1143-1 are not two points on one scale.
Two questions to settle first
What does your insurer require? The sum held overnight sets the grade, and the insurer sets the relationship between the two. Get that figure in writing before you shortlist — it is the only input that can force the decision, and it is cheaper to hear early.
What can the floor carry, and how does the safe get there? Weight is the constraint that most often changes the answer late. A stairwell turn, a lift capacity or a first-floor slab can rule out a body that was otherwise correct. That is what a site survey is for, and why we do one before an order rather than after.
Once those two are answered, the grade is usually obvious.