What is a waaierzwik?
A waaierzwik (Dutch, literally “fan spandrel”) is a fan-shaped ornament in the spandrel of an arched transom light or a round-arched window above a door or window. The glazing bars or mouldings in the curved top part of the frame radiate from one point, forming a half fan or sunburst, much like a classic fanlight. It is often seen on windows with a sliding sash, where the curved top part is fixed.
How to recognise it
- Location: in the semicircular or segmental top part of a window or door opening.
- Form: timber glazing bars or mouldings radiating from the middle of the bottom edge to the arch, sometimes with a half rosette at the centre.
- Combination: frequently above a sash window or a panelled door in 18th- and 19th-century facades.
Restoration tips
- Record the existing shape with photos and a measured drawing or template of each bar before dismantling anything. The angles between the bars are rarely all equal.
- Repair rather than replace. Rot usually sits at the bottom, in the sill of the transom light and the feet of the bars. Cutting out rotten wood and splicing in new wood of the same species keeps the original detailing.
- Keep the glazing in proportion. Insulated glass often requires thicker bars; thin heritage double glazing exists for slender historic bars. For listed buildings, consult the local authority first, as changes usually need consent.
- Maintain the paintwork regularly: the many joints between bars and glass are prone to water ingress.
Related terms
- Transom window
- Round arch
- Sliding sash window
- Tracery
- Y-tracery
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