A casement window is a window type that swings open on a vertical hinge axis, similar to a door, and can be hung to open either inward or outward. It is one of the most common window types in housing and provides a large ventilation opening.
How a casement window works
The sash hangs on two or three hinges along one side of the frame. Turning the handle releases the multi-point lock, after which the sash can swing fully open:
- Inward opening — common in Dutch and German new build, easy to clean from inside
- Outward opening — traditional in the UK and old townhouses, no loss of internal space
Parts of a casement window
- Frame — fixed surround in the wall
- Sash — the opening leaf containing the glass
- Hinge (butt hinge, paumelle) — connection between frame and sash
- Handle and locking gear — multi-point lock with pins engaging in the rebate
- Rebate and weather seal — sealing when the sash is closed
Applications
Casement windows are used in:
- Living rooms — often combined with a fixed bottom light
- Bedrooms — for strong ventilation, sometimes as a tilt-and-turn
- Kitchens — for quick air changes
- Heritage buildings — historic stained or leaded windows often hung as casements
Comparison with other window types
| Window type | Motion | Use |
|---|---|---|
| Casement window | Vertical axis, side | Ventilation and access |
| Tilt window | Horizontal axis, bottom | Safe ventilation |
| Tilt-and-turn | Both motions | Combination |
| Awning window | Horizontal axis, top | Classic facades |
| Sash window | Vertical or horizontal sliding | Space-saving outside |
Related terms
- Tilt-and-turn window
- Tilt window
- Window frame
- Hinge
- Awning window
- Window hardware
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