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Have you ever wondered what relevance an Italian designer, the early Egyptians, The Great Fire of London, and the developments of glass production, has had on the fabric, structure, and construction of today’s buildings and how these seemingly unconnected events have influenced the development of sash windows?

There cannot be a more quintessential British style of window, simple in design, elegant in proportion, sash windows remain the most beautiful and naturally effective style of window, ever made. That’s why their design has remained so popular and has traveled the world over, especially those parts of the Colonies, India, Australia, and the United States.

Although no record exists of who the inventor was, sash windows seem to have first appeared in the mid-1600s, and very soon this evocative style became very fashionable with royalty and landed gentry. The earliest known examples at Ham House, Hampton Court, and Kensington Palace circa 1670-1680.

Whilst the early Egyptians (7th and 8th century BC) are credited with inventing glass for early lenses, Palladio the Venetian scholar developed his theory around 1550, becoming popular in the mid 17th century. Believe it or not, the replacement window market was founded in the 18th century!

There are examples of new windows replacing older ones, it was very fashionable to replace wrought iron or cast-iron, metal casement windows on the front elevation of a building, with small leaded light windows (in 16th-century properties) or with wooden sash windows, as these new products were aesthetically very pleasing and immensely more efficient ventilating the rooms.

Homeowners wanted to emulate the rich merchants building grand townhouses and stately mansions to display their wealth. The larger the glazed area of the windows in their mansion, the wealthier they were. Hence the window tax first imposed in England in 1696. It was eventually repealed but after being “the primary cause of much sickness and mortality’ through poor ventilation

The Great Fire

The prominence of oak timbered box sash windows, timber shop signs, and exposed beams, which were all generally fitted on the front face of buildings, meant the spread of fire in 1666, was able to spread rapidly across London affecting many buildings.

This event alone is probably responsible for changing the architecture of so many of today’s buildings because within 50 years or so,  London changed its Building Regulations (1709) insisting that timber windows must be recessed back at least 4” from the face of the building, and then (1774) that sash windows should be behind the outside face of bricks, thus reducing the threat of fire considerably.

Many followed this new construction style, as it maximised daylight, solar gain, and ventilation, properties which are still important today.