Window replacement prevention from falling

Part K

Provision should be made to ensure that protection from falling is made no worse as a result of a replacement glazing installation.

Domestic and non-domestic buildings

In some situations existing windows act as guarding to prevent building users from falling. In such situations replacement windows should continue to provide appropriate guarding to the bottom edge of a window, opening or otherwise, to ensure protection from falling.

It is recommended wherever possible that guarding is installed to the current minimum size.

Typically accepted standard – current requirements

Ground floors with basement wells or sunken areas next to the building and all upper floors should be provided with ancillary guarding where minimum floor to sill or floor to opening casement heights are less than:


  • Windows/rooflights to loft conversions - 600 mm  
  • All other window/rooflights - 800 mm.  

Note. Fixed glazing panels below 800 mm may also serve as guarding provided they are sufficiently robust.


  • All guarding should be at least 1100 mm high.
  • Windows and Doors (where relevant)
  • Replacement glazing should meet the current minimum standards.

Updated: 5 August 2009