08.07 Safety glazing

Categories: Glass & Glazing

Introduction
Glass and glazing materials have to be safe in the event of impact by people and others.  This section describes the requirements for safety glazing and the use of safety glazing.

Other safety issues include fire (Section 08.10) and falling glass (Section 08.08).

Safety glazing
Safety glass is defined as glass that:

• Breaks in a safe way

or
• Does not break under impact

Toughened glass to BS6206 is a safety glass that fails by breaking into small semi-angular fragments that cause little harm unless falling from a great height in a concentrated form.  To comply with BS6206 a toughened glass must break such that the mass of the 10 largest crack free particles is less than the mass of a 6500mm² area of the original sample.

Glasses that do not break under human impact include thick sheets of annealed glass, laminated glass, plastic glazing materials and some wired glasses.

BS6206 describes an impact  test in which an impactor is alowed to swing against the glass.  The categories given in BS6206 are:
 

A safety glass only complies with BS6206 if it is marked in a permanent manner showing the classification achieved.
 

Building regulations
Requirement for safety glass
The building regulations Approved Document N defines critical areas in which safety glass must be used.  These are the areas that may be struck by a person falling or mistaking a doorway.  Critical areas are:

• Any glass below 800 mm above finished floor level, image.
• Any glass below 1500 mm above finished floor level and, image;
• Within a door
• Within 300 mm of a door

However, glass within a door does not have to be a safety glass if the glass is no more than 250 mm wide, image.  Generally glasses should meet the requirements of Class C of BS6202 unless they are greater than 900mm wide in which case they should meet the requirements of Class B of BS6206.

The Building Regulations allow the use of plain annealed glass in all areas such as shop fronts provided it is strong enough to resist impact.  This requires that the size of the glass sheet is limited according to its thickness as follows:
 

For an insulated glazing unit both sides of the unit have to comply with Part N of the Building Regulations.

An alternative to using safety glass is to put a barrier in front of the glass to prevent impact against the glass.  Part N of the Building Regulations requires protective barriers 800 mm  high with a maximum opening of 75 mm in the absence of safety glass, image.
 

Glass manifestation
To reduce the risk of pedestrians wlking into glass walls and doors Part N of the Building Regulations requires that glass is marked in a way that it can be clearly seen.  This 'manifestation' as it is known has to comply with the dimensions shown here.  It can take any form and may be simply aesthetic or may be a company logo or similar marking.