Steel Side-Hung Windows – Outward Opening


Also known as the casement window, its sash is attached to the either side of the frame and opens outward. Depending on the design requirements, friction stays or butt hinges are used for hinging the sash to the frame.

With their slim sightlines, steel side-hung windows offer a sleek and modern aesthetic in buildings. Their versatility makes them suitable for various architectural styles,  from classic to contemporary homes.

Design and Aesthetic


  • Thermally broken profiles as standard 
  • A basic depth for thermally broken steel windows is between 50-70mm.
  • Slim sightlines

Materials and Surface Finishes


  • Strip galvanised steel (Allowing full range of standard powder coated RAL colour options)
  • Corten
  • Stainless steel
  • Marine grade powder coated for for use in marine and coastal environments

Size Limitations


  • Standard sash sizes for steel side-hung window are up to 1 metre in width and 2.3 metres in height.
  • A steel side-hung window sash may weigh up to 150kg. 

Opening options


  • Outward opeing side-hung window (with visible butt hinges)
  • Outward opeing side-guided window (with concealed friction stays)
  • Outward opening double side-hung window (also called french windows, no mullion in the centre when both sashes are open)

Safety & Security Options


  • Steel side-hung windows are usually come with multi-point locking systems as a standard feature.
  • Security options include burglar resistance classes of RC2, RC3 or PAS24.
  • Restrictors can be installed on steel side-hung windows to limit the amount of opening for safety.
  • Laminated glass is chosen for the steel side-hung windows requiring extra security.
  • For cases like full height glazing where containment is needed, laminated glass is used for preventing fall through.

Glass Specification


  • Steel side-hung windows can be glazed with double or triple glass units. 
  • Double glass unit: Ug-value of 1.0 W/m2K, built with 4 or 6 mm toughened glass, argon filled cavity, Ug-value of 1.0 W/m2K, low-e coating, warm edge spacers. 
  • Triple glass unit: To achieve better thermal performance (Ug-value of 0.5 or 0.6 W/m2K). 
  • Toughened safety glass: Glass units are built with toughened glass
  • Laminated glass: One pane of glass unit can be built with laminated glass for additional security, safety or noise reduction.

Thermal Performance


  • External steel windows are usually constructed with thermally-broken frames to achieve higher thermal insulation.
  • For existing residential buildings, a steel window must have either a Uw-value of 1.4 W/m2K or lower, or WER Band B to comply with Part L of Building Regulations.
  • For new residential buildings, a steel window must have a notional Uw-value of 1.2 W/m2K (with limiting value of  1.6 W/m2K for SAP calculation) to comply with Part L of Building Regulations.

Product range


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Buyer’s Guide to Steel Windows



Building Regulations for Windows

All windows installed in buildings must comply with the Building Regulations and meet the specified requirements:

  • Windows to be installed in new or existing buildings must meet energy efficiency requirements contained in Approved Document L.
  • In new residential buildings, easily accessible windows are required to meet the security requirements specified in Approved Document Q.
  • Windows must comply with ventilation requirements specified in Approved Document F.
  • Glazing in critical locations must meet the safety requirements specified in Approved Document K.