Glass is one of the most significant additions to modern architecture and continues to be one of the most used non-structural materials in building envelopes. Many magical properties of glass provide architects with flexibility and opportunities in design such as, provision for natural light, transparency, absorption/reflection of heat and more. However, the fragile and delicate nature of glass makes it a concern for safety and requires regulations and specifications around the usage of glass. In contemporary times, with the help of technological advancements, stronger, safer and secure versions of ordinary glass are developed.
What is safety glass?
Safety glass or reinforced glass is a special kind of toughened glass which is used to reduce the risk of injuries caused due to the breaking of glass in an accident due to impact or in case of fire. This kind of glass is almost 4 or 5 times stronger than regular glass and can withstand impact up to a certain level, but its main purpose remains to decrease the possibility of injury.
What is secuirty glass?
High security glass on the other hand is a stronger glass which along with reducing the risk of injury has higher capacity to withstand intentional attacks, manual or ballistic in nature.
Classification of safety glass - BS EN 12600
The British Standard for classification of ‘Safety Glasses’ is BS EN 12600. BS EN 12600 specifies a pendulum impact test method for single flat panes of glass for use in buildings.
This standard classifies flat glass products in three principal classes by performance under impact and by mode of breakage.
Classification of safety glass is expressed in the following form:
α - is the highest class of drop height class at which the glass either did not break or broke safely.
β - is the type of breakage.
φ - is the highest class of drop height class at which the glass did not break or broke safely and remained in place.
α is the drop height class at which the glass either did not break or broke safely:
- Class 1 = 1200 mm
- Class 2 = 450 mm
- Class 3 = 190 mm
There are three types of breakage (β)
|Types of breakage
|Numerous cracks appear forming separate fragments with sharp edges, some of which are large
|Annealed (float) glass, heat-strengthened glass
|Numerous cracks appear, but the fragments hold together and do not separate
|Laminated glass, wired glass, annealed glass with applied safety film
|Disintegration occurs, leading to a large number of small particles that are relatively harmless
|Toughened glass (Thermally toughened)
Toughened glass classification
Toughened and toughened heat-soaked glasses meet the criteria set out in standard EN 12600.
Laminated glass classification
Laminated safety glasses are classified as follows in line with standard EN 12600.
Building regulations requirements for safety glass
Requirements for safety glass are monitored by Part N of the Approved Documents of the Building Regulations. According to which, a safety glass should follow at least one of the following conditions:
- Exhibit resistance to the impact without breaking
- Failing to resist without breaking, it should break in ways that minimises the risk of injury.
- Stays shielded or protected from the impact.
In locations where the glazing is transparent or in commercial or institutional applications, features like markings or transfers should be incorporated to make it clear to people moving around the glazing area.
Where to install the safety glass?
Building Regulations Part K4 requirement defines certain locations as “Critical”, where use of safety glass is warranted to protect people from getting injured.
The following are considered as “Critical Locations”:
- Low level areas: Glazing areas which are wholly or partially within 800 mm from finished floor level. (In above diagram: 6, 7, 8, 11)
- Doors: Glazing areas which are wholly or partially within 1500mm from finished floor level. (In above diagram: 5, 8)
- Side panels adjacent to doors: Areas which is wholly or partially within 300mm of the edge of a door and which is also wholly or partially within 1500mm from floor level. (In above diagram: 2, 7 and 4)
- Bathroom Areas: Shower screens or other areas where there is a risk of slipping on wet floor and accidental human impact into a glazed surface, should all be safety glass.
- Protective Barriers: Balconies, railings on staircase or landings should be fitted with safety glazing.
- Furniture and Cabinets: Safety glass should be installed in tables with glass tops, mirrors, shelves and cabinet doors.
To comply with Critical Locations glazing requirements, standards and other codes is the responsibility of the user. It should be noted that the Building Regulations only monitor the glazing that is a part of the building structure and Part 4: 1994 of BS 6262 sets the requirements of other locations.
For further information
For more information, visit the links below:
- CWCT (Centre for Windows and Cladding Technologies)
- Note: BS EN 6206 (Withdrawn in 2006 and superseded by BS EN 12600)