The Thrill of the Cill

Cills are an essential component for all window and bifolding door systems. Cills mainly serve to direct rain water away from the wall beneath a window or door, protecting a structure’s interior and all its inhabitants. However, cills also aid towards the structural integrity of a window load while providing additional visual and decorative purposes.

  • Our aluminium cills are available in a range of colours and sizes to suit the vast majority of fabrication systems. With a current lead time of 5-7 working days, our cills are not only rapidly available they also offer many outstanding technical values.
  • As a universal ancillary product, we can offer our cill range in mixed stillage format. Offering further bulk savings with a range of mixed stocked colours within the stillage.
  • Stock colours: 7016 Grey, 9005 Black, 9016 White, Grey on White dual colour, Black on White dual colour, textured Grey 7016


The main purpose of a cill and by far its greatest benefit to any glazing fabrication. Without the humble cill, moisture, rain and snow would seep into a building’s structure causing issues of mould and rot. The simple yet brilliant design directs water away from the window or door track, effectively keeping interiors dry and leak-free. Our cill’s overhang is also a vital water protection feature. Providing further weather protection to the surrounding walls. Our range can accommodate a concealed drainage feature from within the chambers, for exceptional hidden weather-proofing.

The side of a cill is wedged between the left and right of a window, creating a complete weather block at the foundation of the pane. Our aluminium cills’ two-layer lacquer coating, with separate burning, creates total resistance to the worst that Great British weather has to throw at it. Our cills utilise aluminium screw-in end caps, rather than traditional uPVC caps which need to be glued on, and pre-drilled screw ports. Ensuring our products remain both strong and robust, while making for a hassle-free fabrication and installation.


Cills also play an important role in a building’s structure. They serve as the framing of a window – keeping it securely in place. Without such, as a foundation shifts and settles, the window would shift too, affecting its normal operation and opening. Thanks to aluminium’s unique combination of lightweight and strong properties, aluminium cills can support the heavy glass and framework of a window or door.

The impressive durability of aluminium can guarantee this stability for a long time. Aluminium cills are built to last and are naturally resistant to corrosion. The life-span of aluminium outlives that of uPVC (an impressive 20-45 years more), and is far less likely to rot or warp than uPVC or timber. Aluminium’s durability and ability to withstand outside elements means the material requires little maintenance. It’s effective against temperature fluctuations and can withstand rain and wind more than competing materials.


Cills serve an important visual purpose. It provides an enhanced overall appearance to a window and can be utilised as a shelf feature, making it the perfect spot for plants and decor. To complement the decorative aspect of cills, our cills with pre-drilled screw ports are finished in a high quality powder coat available in Black, White or Anthracite Grey. Powder-coating creates a robust finish which is highly thermal and UV and corrosion resistant, lasting for many years with minimal maintenance.

Our cills are universal to match many bifold or window systems, including Alutech’s BF73 bi-folding door and window range. Our new range is available in a variety of different sizes, ranging from 90mm to 230mm and can be ordered with or without pre-drilled screw ports.


Despite the current unprecedented environment, we can offer fantastic lead times on our new range of cills. Your custom-made cills will be ready for you to use on-site within 5 to 7 working days from ordering, helping you to meet your fabrication and installation needs.

For more information on our range of aluminium cills view our product range or give our friendly sales teams a call on 01924 350110.

Related Posts

Are Aluminium doors and windows sustainable?
Alutech bifolds
Alutech impresses at Harrogate home
Leave us a Review on Trustpilot
Sign up to our mailing list

Signup today for free and be the first to get notified on new product updates and news from Alutech Systems.

Sign up