Floating an idea

Architectural glass specialist OAG gives an insight for designers into the possibilities, as well as practical implications, of ‘oversize’ glass float runs

During the past two decades, feature glass entrances and double height ground and first floor facades have risen in popularity. Due to this increase, glass itself is becoming synonymous with some of London’s best-known landmarks and prestigious institutions. From over 13,000 m² of glass being installed at the Battersea Power Station redevelopment in phases two and three, to the 250 metre long facade at London Bridge station, new build and redevelopments alike are becoming accustomed to the increasing trend for stronger, larger higher performing glass types. For both domestic and multinational contractors sourcing, designing and installing oversize glass units is a challenge in itself.

Within the specialist glazier trade, handling and situating oversize glass is now a necessary part of firms’ repertoire, with demand ever-increasing. From 7 metre high glass fins on the recent Aviva Tower project, to 7.6 x 3 metre toughened panes at Warner Bros Head Office, Grays Inn Road, the bespoke and oversized nature of the glass specialists now have to handle makes them the authority on ‘Jumbo’ glass sheets, measuring 6000 mm x 3210 mm. Sheets over this size are produced subject to the manufacturer initiating an oversize ‘glass float run’, usually only permitted three or four times a year. However, as manufacturers plan oversize runs, they canvas the glass processors to gauge what the demand is. If there is sufficient demand, they will then carry out the scheduled run. Other factors such as strong buyer relations often also influence the outcome. Buyer relations are paramount for glass suppliers in approving float runs, as they must have unwavering confidence in the supplier’s ability to handle, install and properly care for the glass provided. During a production run, when the glass sizes proposed are over and above standard jumbo size, often the actual make up of the DGUs (double glazed units) still needs to be determined. Glass specialists can engineer this throughout the design process – finite calculations are prepared to suit the specification requirements. A vast number of methodological deliberations must be taken into account, outside the ordinary construction compliance. On site logistics must be carefully thought over, especially when delivering oversized DGUs into a built-up area.

Road closures lift options and weight must all be high up on your glazing specialist’s agenda. All this highlighting the importance of early involvement and logistical planning as well as well trained specialist on site operatives to carry the task, from delivery right through to installation. When minimising risk, the worst-case scenario must always be the starting point for any method statement, outlining the most hazardous dangers first. For example, when contemplating safety within a glass lift plan, risks can be minimised when determining the makeup of the DGU itself. Laminated glass panes will not shatter, helping prevent an unsafe site environment as well as avoid delaying yourself and other contractors. Laminated DGUs only crack within the laminate and glass will be retained within a single pane. This demonstrates a risk that can be eliminated not only in the logistics, but as early as the design phase. For example, the DGU is likely to be made from glass sheets laminated together on both the outside and inside faces. The thickness of glass panes such as these is something that was determined through innovative design engineering. The glass thicknesses and DGUs will be prepared and specified to project-specific requirements before approaching the glass processors and seeking float run availability and subsequent time frames. This would normally be tackled by appointing a glazing specialist early, so that the design and engineering process can be progressed. The advantage is you can plan well ahead and tie into an oversize float run at the first opportunity. Load bearing on glass sheets needs to be high on the list of design considerations.

Glass fins and support systems are becoming more common within glass feature entrances and facades. Structural glazing specialists can advise on considerations and limitations of structural glass support structures and should be heavily integrated with your team during the design phase right through to handover. Glass ordered well in advance can be stored and held in reserve – this is common practice for specialist glaziers and also allows a thorough product check of all units prior to install. This minimises the risks associated with availability and potential postponement of a float run through lack of demand. Glazing specialists also allow inspection by all involved parties to minimise any risk of wasted time and resource on busy, multi-contracted sites. After the glass is received well ahead of time, specialists are able to observe and plan with the glass coating plants, who have distinct criteria for oversize coating runs. They are applied to certain surfaces of the glass to assist with solar and thermal control; in addition anti-reflection and self-cleaning coatings are becoming more common in today’s market. Again, these coatings are run on cycles and require well thought out logistical planning and resource allocation to achieve the required finish.

The emphasis has to be on engaging with design process early, which permits a longer, more methodical lead into the oversize campaigns and coating runs. This allows all risks associated with the manufacture and installation of oversize glass to be managed and minimised.