A cloister window — Dutch kloostervenster or kloosterkozijn — is a window type with two roughly equal openings stacked one above the other within a single frame: the upper opening was glazed, the lower one originally closed with a timber shutter. A horizontal transom (Dutch kalf) separates the two.
The layout is purely practical. The upper light gives daylight even when the shutter below is closed; the lower opening provides ventilation and can be shut against weather, prying eyes and intruders. Glass was expensive in the sixteenth and seventeenth centuries, so glazing only the upper light kept a window affordable.
How it differs from related types
- Cross window — divided by both a mullion and a transom, giving four openings: two glazed lights above, two shuttered below
- Bolkozijn — the glazed part and the shuttered part sit side by side rather than stacked
- Cloister window — two openings stacked, with no central mullion
Where you find it
- Dutch Renaissance — the type appeared around 1520 and stayed in use for roughly two centuries
- Houses, farmhouses and gatehouses in brick architecture
- Restoration work on historic facades, where the window type is often a listed characteristic
- New build in a historic idiom, for example in conservation areas
These frames often carried load, which is why they are heavy in section: the brickwork above bears on the head of the frame or on a relieving arch.
Practical tips
- Do not change the subdivision — removing the transom or glazing the lower opening destroys the character and normally needs consent on a listed building
- Check the transom and the sill first — that is where water stands and where rot starts
- Use durable timber — oak or a hardwood with a good durability class for the weathered members
- Insulating glass is usually too thick for original slim glazing bars; secondary glazing or thin insulating glass are the common alternatives
Related terms
- Cross window
- Window frame
- Transom
- Leaded glass
- Shutter
- Relieving arch
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