To the layman, a fully-glazed office building with its coat of glittering aluminium and glass is the epitome of modern building design. But in the world of curtain walling, as with every industry, some systems are more cutting-edge than others.
The traditional method to curtain walling – the so-called ‘stick’ system in which individual panel components are assembled and installed on site – can produce building envelopes that are as technically advanced as they are visually striking.
But UK specifiers and designers are increasingly looking to off-site production to keep ahead of changing Health and Safety and quality criteria.
The UK cladding market is well adapted to the traditional stick system. This is designed by the manufacturer which supplies the extruded profiles and ancillary products to its client, the specialist curtain walling contractor. The client then uses these components to manufacture the elements which create the facade framing according to the design.
Pre-manufactured or ‘unitised’ curtain walling systems effectively take the construction off site. Instead of delivering stock lengths of extruded profile, the company supplies its client with fully assembled glazed panels.
Such is the growing demand for unitised curtain walling systems that leading architectural aluminium systems supplier Kawneer, a global player in curtain walling and part of the multi-billion dollar Alcoa group, has set up a new division in the UK to address it.
Based in Birmingham, the new UK office of Kawneer Global Special Projects (KGSP) is targeting curtain walling contracts where the benefits of unitised production will bring significant advantages over the traditional stick systems.
In terms of speed and efficiency, the benefits of unitised systems can be enormous. Joe Bandy, director of technical sales with KGSP, explained: “A stick system gets to site quicker – typically within 16 to 20 weeks of the order being placed – whereas a unitised system will take 30 to 36 weeks”.
Once on site however, it is a different story.
“A stick system can be installed at a rate of around 50m² a week but a unitised system can be installed at up to 75m² to 150m² a day, depending on the complexity of the application,” said Mr Bandy.
This massive acceleration in installation time more than compensates for the extra time it takes to deliver the system to site. Furthermore, in an integrated construction team where key sub-contract packages are let very early in the design stages, off-site production can easily be scheduled to allow the curtain walling to be delivered promptly on the fastest of fast-track programmes.
The efficiency gains achievable with a unitised system are enhanced by better quality control. Carrying out design, engineering, manufacture, assembly and glazing within its own off-site manufacturing facility gives the manufacturer unprecedented control over the production process and minimises the risk of defects appearing further along the supply chain.
Clients of KGSP estimate the off site process is four to five times quicker than traditional stick systems, taking into account assembly, glazing and installation.
Although unitised curtain walling is hardly new (Kawneer in North America has supplied unitised systems across the world for at least the past two decades) in the UK it is a concept whose time has come.
The so-called “Rethinking Construction” movement, inspired by a critical report published by former Jaguar and BAA chairman Sir John Egan in 1998, encourages the greater use of off-site manufacture and just-in-time delivery as a way of improving productivity and reducing construction defects.
At the same time, industry-led initiatives to cut the number of construction deaths and injuries have also championed off-site manufacture on the basis that it greatly reduces hazardous site work and the dependence on site-based labour. Unitised also takes away the need for scaffolding which has the advantage of a safe working environment and significant cost benefits.
