The site is part of the redevelopment of East London in preparation for the 2012 Olympics due to take place in London that summer.

Balcony Systems was involved in the supply of over 4500 meters of their unique glass railing system and a special facia solution for the balcony structure.

Over 6 different special aluminium profiles were specifically extruded for this project. Handrails were finished in Balcony’s proprietary handrail finish called “Royal Chrome” which the architects found extremely pleasing.

The fascia were finished in a metallic anodize colour that uses a special method to break the light giving it a blue-grey colour.

The glass railing were required to use laminated toughened glasses so the balconies conform to both European and British standards:

A beautiful apartment block with over four hundred meter of glass balustrades were supplied and installed in this project.

The developer, Hamlet Homes, had previously encountered problems with staining and corrosion on stainless steel balconies they had manufactured on a different project that was also in a marine location nearby.

They chose Balcony Systems Royal Chrome handrail system for the glass balustrades after seeing the advantages both in the look and also in the long term resistance to the salty air environment.

Many complex curves and “S” type bends on the top level terraces required some experienced surveying and precision manufacturing.

The results are delightful and parties are well pleased.

Aesthetically however tea staining is not ideal, and so the information herein is in an attempt to help identify the causes and suggest possible solutions.

Stainless Steel

The term “stainless” steel derives from the development of the speciality steels for modern cutlery industry. It has now been adopted as a generic name for steels developed for any corrosion or oxidation (rust) resistant applications.

The corrosion resistant characteristics of stainless steels are a result of chromium-rich oxide film that forms naturally on the metal surface. Although this film is extremely thin, it is chemically stable and ‘self-repairing’.

Other types of steel such as mild steel suffer from general corrosion where large areas of the surface are affected, but stainless steels, due to their oxide film, are normally resistant to this form of attack.

Common stainless steels used in the enclosure industry are 304 and 316. Both are iron alloys with additional chromium, and nickel. The nickel content in 316 grades is slightly higher than with 304 grades, and the chromium content is slightly lower. However, the most important difference is that the 316 grades have molybdenum as an additive, to improve its resistance to pitting corrosion, which is usually the result of chloride or saline attack. 316 stainless is preferred by balcony and handrail manufacturers due to this superior corrosion resistance, even though it is a higher cost material.

Tea Staining of balcony handrails

Tea staining can be defined as the “discolouration of the surface of stainless steel mainly as a result of chloride attack”

As a first step it is useful to try to understand why, and in what circumstances tea staining can occur. Tea staining of stainless steels is a phenomenon that occurs where water with significant chloride content is in regular contact with the metal surface. This is a common occurrence along the coastal areas of the United Kingdom.

How is tea staining caused?

Although research on the root cause of tea staining has been limited, there seems to be little research on the root cause of tea staining. However the mechanisms involved can be inferred by the pattern of the corrosion, and known factors that can help counter the effect. One of the most common factors linked with tea staining is the surface finish of the material. Smoother, polished surfaces often do not show any signs of staining, so from this it can be said that grooves or troughs in the material are a root cause of the problem. Surface roughness (Ra) is measured in units of micrometers (µm), and is defined as the average deviation of the height of the surface from the mean height. Higher Ra values or irregular profiles are often associated with increased tea staining.

It is reasonable to assume that the base cause of this corrosion is similar to that of many of the other common types of corrosion. The association of tea staining with proximity to salt water means that chloride attack is the most likely cause of the problem. However you would not normally expect the low level of chlorides present in sea water, for example, to have such a dramatic effect. The reasons why this occurs can be deduced by the locations and one of the solutions to tea staining problems.

Reducing the effect of tea staining on stainless steel balconies

One of the most common ways to prevent problems associated with tea staining on stainless steel balconies is to ensure that the surface is washed regularly with fresh, clean water. This would infer that the corrosion is being caused not by the initial contact with salt water, but with deposits of salt building up on the surface and pours of the handrails. Though microscopic the chloride concentration would build up in any surface troughs. As the water evaporates it leaves a deposit of salt in the trough, and the next time the surface becomes wet this deposit concentrates the chlorides naturally present, and increases the corrosive effects. Over time therefore the chloride concentration in these troughs can become high enough to cause corrosion. Note that this would be consistent with the effect that an increasing surface roughness will have on the tea staining effect, i.e. a deeper groove will trap more salty water, which will give a higher chloride concentration.

The location of particular areas prone to tea staining also implies that higher temperatures and humidity have an effect, as does intermittent exposure (for example, spray from rough seas). High temperatures increase the rate of corrosion, but elevated humidity will increase the time taken for the water on the surface to evaporate, and hence increase the time that the higher concentration chloride solution will be in contact with the metal, and it is this contact with the solution that causes corrosion rather than with the resultant solids.

When ordering stainless steel balconies and handrails, the following is a list of factors that should be considered in particular in areas close to the ocean, or where high levels of chlorides occur naturally, or are found in wash waters.

This starts with basic initial material selections, and proceeds into maintenance of the balustrades to ensure a long life, and therefore maximum value for the balcony.

Material Selection – Initial material selection for the enclosure is of critical importance to the longevity of the balustrades. Stainless steel of grade 316 or above should be used as minimum, as lower grades such as 304 are significantly less resistant to chloride attack due to the absence of molybdenum.

Surface Finish – The rule of thumb for surface finishes is that the smoother the finish, the better will be the resistance to tea staining.

Cleaning stainless steel handrails – Regular washing with clean, fresh water or even rain water has a significant effect on reducing the incidence of tea staining in the environments that can cause concern. Where tea staining still occurs despite regular washing, additional protection can be provided by a special coating procedure using a bespoke polymeric resin

Conclusion

Tea staining of stainless steel handrails, balconies and surfaces can be a problem where there are significant levels of chlorides in water that comes into contact with the metal surface. This can be around the coastal locations, or in the interior where ground water contains significant chlorides. Although it does not look very pleasant it tends to be a surface phenomenon only, and does not affect the structural integrity or longevity of the balcony. The cause of tea staining has been examined in some details to help evaluate the potential remedies for the condition. Recommendations to help prevent tea staining include correct specification of the grade of stainless steel to be used, surface finishes to help reduce the problem as well as maintenance procedures, and preventative coating treatments.

This is the traditional and frequently seen solution for balustrades, glass or not.

Resisting the loads

The glass balustrades supplied by balcony systems has broken this routine and introduced a refreshingly innovative approach to resisting the loads. Rather than cantilevering the load and thus needing to design a very rigid base the handrail is designed to take loads direct at the design height.

Fixing the handrail to the falls allow the handrail to work as a rigid element which resists the loads. When corners are introduced the special way the handrail parts are connected and the way the glass is continuously silicone sealed to the glass along the long edge of the glass uses the shearing load of the glass from the handrail right down to the base rail. Again this “out of the box” approach allows for clean glass corners and for cornered balconies to require less posts than ever.

Spreading the resistance across the curve

To top these designs some curved balconies, depending on the radii, are amazingly strong without posts! The curved glass railing is a very stable element to the greater ability of the curve to resist a load by way of spreading the resistance across the curve, similar to a brick arch. In addition the glass itself lends additional horizontal support in a fashion that each curved glass panel cannot bend along the vertical side.

Glass balustrades are also available from stock or custom made to suit the style and size of property. Available in curved, stepped or straight designs, balustrades add great character and style to homes. And with our systems there are no clamps between each pane of glass to disturb the view and the glass reaches top to bottom to give an uninterrupted, clearer view. Using the same minimal hand rail as the Juliette balcony and available in easy maintenance anodised aluminium, Balcony’s Juliettes and balustrades are easy to install and offer instant improvement to the look of any property.

Balcony is the UK’s leading supplier of curved patio doors and our stunning range is described by homeowners, builders, installers and architects as giving properties the ‘wow’ factor. Each door comes with high weather rating, thermally broken aluminium profiles, multi-point locking, 28mm double curved glazing with safety glass on both sides and a choice of RAL powder coat colours. A special low maintenance coating is available for the external surface of the glass to minimise the need for cleaning.

When it came to choosing the balustrade he knew exactly what he wanted and chose leading supplier Balcony Systems Ltd. The clean lines and round handrail coupled with the uncluttered finish matched the modern exterior. Most importantly, with no clamps or ugly fittings to get in the way the balustrade didn’t interrupt the spectacular view of the coast from the glass-walled sitting room.

A complicated design

Twenty eight metres of balustrade was ordered for the project, Mike Murray explains: “Balcony’s products are very easy to assemble and install yourself but because our design was quite complicated, it may have been better with hindsight to use a professional installer!

“A challenging bit was the slope leading up to the house where the glass had to be cut at an angle to fit the slope,” continues Mike. “The installation was also on natural stone paving which is not a smooth surface. Accurate measuring and cutting was vital, but Balcony helped me at every stage. They even made a mock-up in MDF to be certain we had it right.”

Great results

The installation took four weeks to complete and Mr Murray was delighted with the end result. “It complements the look of the house and adds to the value. I’d happily recommend Balcony’s products and service.”

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.

Required pressures

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;

1. 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)
2. 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.