Aluminium cill types for windows

By covering window outdoor area, window sills prevent water flow from entering into the premises and protect the window structure against moisture and premature destruction. Windows sills provide also aestetic look for the windows and building. 

Window sills are installed together with windows into the bottom part of window opening. They come in various shapes and made from usually 2mm aluminium sheet. They can be supplied in any RAL colours.


Aluminium sill types for windows

There are three types of sill types for windows: 

  1. Sub-cill: This is the most comman type of cill and it sits beneath the window frame.  The measurement of an aluminium sub-cill is taken from the back of the cill to the front of the drop-nose.
  2. Extension cill: An aluminium extension cill locks in behind a drip on the window or door.  
  3. Cill pressing: Usually designed and fabricated to bespoke dimensions, cill pressing is fixed to the bottom part of window frame with screws. 


Measuring for window cill pressing 


Part of a window sill: 

  1. Upstand (back fringe): Standard upstand is usually 25mm. 
  2. Overhang 
  3. Front downstand (drip cap or front fringe): Standard downstand is usually 25 or 40mm. 
  4. End cap


Depth: From the front edge of the window to the external face of the wall.

Drip cap: 



the edge of sill projects 30 mm past the face of the wall. 


Taking measurements for window sills 

You need to measure the following: 

Depth of the sill: The depth of the sill depends on where the window is sitting within the opening. 

The length.