What pressures or “loads” do railings and balustrades need to withstand and how are these applied, tested or calculated?
Balustrades and railings are put in place with the basic purpose to protect users of buildings, and other areas, mainly from the danger of falling. In order for the railings to do this they must be designed and built not only to resist pressure on them but also impact.
No matter the materials that make up the balustrade; stainless steel, aluminium, glass or other metals the railing must resist pressure and impact. In order to make sure building users are safe, specific standards and codes of practice have been drawn up to give guidance and limitations as to the level of pressure and impact required on safety railings and balustrades. This is further detailed and specified to different areas and usages of buildings. The reason for this is clear as you would not expect a railing in your lounge to need to be as strong as in a public mall.
In the standard these loads are expressed in kN/m (kilo or thousand Newton meter) in simple terms this is a quantity very similar to 100Kg (220lb) of pressure per meter length. If for example it is stated that there is 1.0kN/m it will be appx the equivalent of 100kg pressure on one meter length.
There are two basic pressures that are required to be met; (a) pressure or load on the handrail of the balustrade and (b) pressure on the material that fills the space (infill) like a glass panel in glass railings for instance. The pressure or load the handrail is a uiformly distributed pressure load on the length of the handrail, basically defining that the load needs to be calculated so that it allows for even distribution of the loads along all the length of the handrail and not add the total load and put it all on one point in the middle of the rail. The lpressure applied to the infill, whether it is glass, bars, metal or plastic, is checked twofold; a spread out pressure and a “point load”. Meaning the glass infill for instance of the balustrade, barrier or railing need to be capable of withstanding an evenly spead out load as well as a sharp concentrated pressure on a small point.
These pressures are tested and calculated insofar as the maximum movement (deflection) under pressure must not exceed 25mm or 1/65 of the length whichever is the smallest.
Standard basic areas
You can say the standard breaks down into these basic areas;
- Private or single family houses for internal stairs/landings etc in which case the handrail loads must be able to take 0.36kN/m For exterior balustrades on balconies or terraces this is doubled to 0.74 kN/m (this can be seen as one person weiging 75kg applying their entire weight on every meter of the handrail – this makes sense as you cannot expect severe overcrowding in a private home)
- Public areas where overcrowding can occur such as retail areas, bars & restaurants the handrail pressure must be able to take 1.5 kN/m. This is further increased to 3.0 kN/m in areas such as malls, discotheques and areas susceptible to overcrowding.
Loadings on the infill
As the point load is the more severe, the loadings on the infill panels of balustrades are as follows:
- Private or single family houses internal stairs/landings etc Point load: 0.25kN/m For external balconies 0.5kN/m.
- On all public areas such as retail areas, malls, discotheques, areas susceptible to overcrowding, bars & restaurants the point load must be able to take 1.5kN/m.
Dealing with glass balustrades
When dealing with glass balustrades one additional element must be taken into the equation and this is resistance of the glass to impact. Ten millimeters (10mm or 3/8th inch) thick glass that has been heat toughened (fully tempered) should be used in areas where there is a space wider than 1.5m.
These are the basics when trying to understand the loads and pressures that railings must resist.