Floors and Stairs

Glass floors and stairs are specifically calculated combinations of glasses designed to create a walkable structure in association with structural supports.

They are designed for pedestrian use only. Underlighting and individuality of design in the production process of the glass allow the interplay of transparency, reflection and refraction of light.

Design criteria

The building use and location define the performance specification. When considering glass as a flooring material, reference should be made to two British Standards which will have a bearing on the installation:

• BS 6399 : Part 1, 1996, Code of Practice for dead and imposed loads, gives guidance to design loads

• BS 5395 : Part 1, 1977:2000, Code of Practice for the design of straight stairs, makes reference to the danger of slippage and specifies minimum coefficients of friction.

Approved Document K of the Building Regulations 1991(1998 Edition), Stairs, Ramps and Guards, controls safety and design.

Firstly, it is necessary to consider the location of the floor and whether it spans a dangerous drop. Breakage of the floor could result in a fall from a high level, or cause injury to the lower leg even when the drop is quite small. The nature of the building and the likely behaviour of its users must be taken into account, with drops in excess of 300mm being categorised as ‘dangerous’.

Other points for consideration are:

  • the avoidance of point or concentrated loadings with hard objects of small contact area, such as castors on furniture
  • artificial lighting beneath glass floors can generate significant heat. Excessive temperatures can cause delamination or breakage of the glass
  • people whose footwear is still wet may walk on glass floors near entrance areas. Whilst the use of small panels and a slip retardant surface such as sandblasted glass may be beneficial, the provision of suitable matting should be considered
  • clear glass floors at high levels may cause users to be nervous. Techniques to help overcome this problem, as well as addressing the issue of modesty, include the use of a grill beneath the glass, a decorated or obscured upper surface, or the use of a tinted or diffused interlayer in the laminated glass
  • fire resistance may be required where the glass is being used to allow light to pass between different floors of a building
  • it is recommended that the nosings of stair treads are protected by a suitable flange projecting upwards from the tread support
  • the design and maintenance specification for the building must allow for the provision of suitable floor protection if heavy pedestrian or other traffic will be passing over the area from time to time.

Glass specification

In most situations only thick annealed glass SGG PLANICLEAR or thick laminated annealed glass SGG STADIP should be considered. SGG SECURIT toughened glass is not generally considered suitable due to its breakage characteristics and subsequent loss of integrity.

A single thickness of glass may be used if the floor does not protect a dangerous drop. For example, where it is required for people to view something immediately below the glass, or for use as a dance floor.

If the floor protects a dangerous drop, which could result in serious injury, a laminated glass is normally required.

If there is no access to the underside a single thickness may be used but with secondary protection by means of a suitable grill 10-30mm below the glass. This grill must be designed to withstand the same loading as the floor together with the weight of the glass. It must be restricted to a grid size which will prevent a foot passing through, with a maximum size of 100 x 100mm.

If there is a risk of a dangerous drop and there is unrestricted access to the underside, such as a pedestrian bridge, laminated solutions must be used. The lower glass of the laminate will prevent glass fragments falling should breakage of the upper glass occur. The use of laminated glass also permits larger pane sizes.

Support structure

The frame should provide continuous support to the perimeter of each individual element of glazing, and must be capable of withstanding both the design loading and the self weight of the glass without excessive deflection.

The weight of the glass may be taken as approximately 2.5kg/m2 /mm of thickness. Therefore 1m2 of 10mm thick glass weighs 25kg.

The frame may be of metal, masonry or wood and the glass must be cushioned from it by 3mm thick neoprene rubber or other material similar in hardness. The clearance between the edge of the glass and the frame, or between adjacent glasses, should be 3mm minimum and infill strips of a material such as wood, cork or neoprene should be inserted to finish just below the upper surface of the glass.

To provide a flush finish a compatible high grade synthetic rubber, polysulphide or silicone sealant can be used as a top pointing. The edges of the glass should be either flat-ground and arrissed or water-jet cut. The frame should support all edges by the overall thickness of the glass as a minimum.

Key criteria when considering glass floors and stairs:

  • Overall size and dimensions
  • Loading details
  • Depth of drop
  • Glass specification
  • Surface finish
  • Fixing substrate

For more information, contact SOLAGLAS CONTRACTING.