A Demerara window is a wooden top-hung casement made of horizontal louvres (jalousies) that swings outwards from the top and is propped open by a stay or hook. The louvred blade allows air to circulate even when the window is partly closed. It takes its name from the Demerara region in former British Guiana (today’s Guyana), where it was widely used in the 18th and 19th centuries.
How it works
When opened, the louvred blade projects outwards like an awning and performs several functions at once:
- It blocks direct sunlight and keeps the room cooler
- It shelters the facade and window opening from driving rain
- Its awning shape encourages an upward airflow (Bernoulli effect)
- The louvres let air through while screening views from outside
Where it is used
The Demerara window is a typical feature of tropical colonial architecture in South America, the Caribbean and parts of South Asia. It is found particularly in:
- Wooden houses — the iconic verandah houses of Georgetown (Guyana), Paramaribo (Suriname) and Willemstad (Curaçao)
- Public buildings — colonial-era market halls, churches and town halls
- Restoration projects — at listed buildings the windows are often reinstated in their original form
In European architecture it is rare; exceptions are mainly colonial-style villas and orangeries.
Construction
A traditional Demerara window consists of:
- A timber frame — usually of locally available durable hardwood
- A louvred sash — with fixed or adjustable jalousie slats
- Two hinges — mounted on the head rail
- A stay — that holds the window open (often adjustable for various opening angles)
- A latch — usually a hook or bolt at the bottom
Heritage value
The historic centre of Paramaribo — a UNESCO World Heritage site since 2002 — protects the Demerara window as a defining element of its wooden architecture. Replacing them with modern windows requires special permission.
Related terms
- Top-hung casement
- Jalousie
- Awning
- Louvre
- Natural ventilation
Want to learn more about construction terms? Visit the knowledge base at Fred’s DIY Plans.