Box sash windows – with their timeless elegance and functionality – are a popular choice to adorn the windows of traditional and modern homes alike. But understanding the intricate workings of these windows can be daunting, especially when each part is so essential to their operation. To keep them going at their best for years to come, let’s delve into the essential components that make a box sash window function.
Where do sash windows come from?
A quintessential British invention that dates all the way back to the 17th century, box sash windows adorn homes up and down the country. Their name ‘sash’ comes from the French word ‘chassis’, which means frame. They have a simple yet elegant design, along with underrated functionality, which makes them a standard feature in British architecture.
The frame
- Box frame: Let’s start with the namesake. The box frame is made up of rectangular timber casing that houses the two sashes (movable panels) and holds all the other components.
- Top rail: The horizontal bar forming the topmost element of the box frame.
- Bottom rail: The horizontal bar forming the bottom element of the box frame.
- Stiles: The vertical members forming the sides of the box frame.
- Apron: The horizontal board below the window, often projecting outwards for water drainage.
The sashes
- Sash: Each movable panel containing the glass panes. Typically, box sash windows have two sashes: an upper sash and a lower sash.
- Meeting rail: The horizontal rail where the upper and lower sashes meet when the window is closed.
- Sash bar: These wooden or metal bars separate the panes of glass within a sash, creating the characteristic grid-like structure.
- Sash stile: The vertical members forming the sides of each sash.
- Glazing: The glass panes held within the sash frame.
The internal operations
- Weight pocket: A cavity within the box frame that houses the counterweights.
- Sash cord: A strong cord connecting the sash weights to the sashes, allowing them to move up and down smoothly.
- Weight: Cast iron or lead weights that counterbalance the weight of the sash, enabling smooth and effortless operation.
- Pulley wheel: A grooved wheel located at the top of the weight pocket, over which the sash cord runs.
- Parting bead: A narrow strip of wood or metal holding the panes of glass in place within the sash.
- Staff bead: A decorative moulding attached to the inside lining of the box frame, holding the two sashes in place and aiding smooth sliding.
Additional components
- Locking mechanisms: Various types of locks can be installed on the sashes for security and ventilation control.
- Horning: A decorative moulding applied to the meeting rails for an aesthetic touch.
- Astragal bars: Decorative bars applied to the outside of the window panes, simulating divided lights.
By gaining a deeper understanding of the individual components that make up a box sash window, it allows you to appreciate the craftsmanship and intricate mechanics that makes them work. Whether you’re maintaining, repairing, or simply admiring these classic windows, knowing their parts unlocks a deeper appreciation for their form and function.
