Due to the diversity of methods used by criminals (axes, screwdrivers, drills, hammers, ram cars, etc), how can a glazing system resist break-in? What standards are applicable?
First, we must understand one essential characteristic of glass, that it breaks. After an impact, a glazing system will show cracks, but may resist break-in by holding firmly in place with no openings through it. The breakages may be large and sharp, targeted around the impact, or tiny and non-cutting in the case of tempered glass (for more information: tempered section).
Second, a glazing system cannot be vandal-proof. This is physically and logically impossible because, after a certain time, a criminal with the right tools will manage to break through the glass. That notion of time is therefore important when talking about resistance to break-in.
There are two European standards for the burglar resistance of glazed building elements. EN 356, which measures only the glass, and EN 1627, which measures the complete glazed solution.
EN 356 subjects the glass to different levels of test to measure glass strengths. The lower levels provide only resistance to vandalism3 and, for breaking and entering, the appropriate resistance levels are P6B, P7B and P8B.
For the glass to reach level P6B, it must withstand at least 31 strikes from a hammer and axe. The glass layers may fracture or break but, to pass, the glass must keep its integrity and not develop an opening. For level P7B, the glass receives 51 strikes, and 71 for level P8B. In each case, it is a purely mechanical test, without any notion of resistance time.