House History Tool – Architecture
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3. Windows
As it’s deemed that ‘eyes are the windows of the soul’, windows are arguably the soul of a building. Everyone needs light and ventilation, and so the technology of windows has been at the forefront of building developments, from stained glass set in lead to hinged wooden casements, sliding sashes, double glazing, and today we can make glass so strong it can be used as a structure in its own right.
As a result, windows can tell you a lot about a house’s history. The sash is perhaps the classic British window, consisting of two halves, set one above the other, at least one of which slides vertically (unless it’s painted shut!). The sash was invented either in Britain or the Low Countries during the middle of the seventeenth century, and in the UK it went on in use throughout the nineteenth century- a tradition of over 200 years. So how do you know if it’s an early or late sash window? The answer could help you to date the house. Well, there were some subtle changes along the way which offer useful clues.
How can you tell if a sash window is early (during their first hundred years of use) or late (the second hundred years)?
There are actually three ways to check if a sash is early or late. The first is to see whether the window is flush with the façade: if it is, it’s usually early.
In London, legislation was passed in 1709 which stated that windows must be recessed into their openings by at least four inches to help prevent fire spreading up the façade, and this rule gradually spread to other towns and cities.
The second clue is to see if there is a thick frame surrounding the sashes: this is called a sash box, made of hollow timber to contain the pulley mechanism. Up to the middle of the eighteenth century the whole caboodle was slotted into the straight sides of an opening in the wall. But in 1774, another round of fire legislation was passed, which said that sash boxes must be hidden in the thickness of the wall so that only the sliding sash frames were exposed to fire. Now, the builders of Bath already did this- but elsewhere, if there’s no sash box visible- it’s late.
The third clue is to check the size of the window panes. Smaller panes set in a 3 across x 2 deep arrangement for each sash tend to be Georgian, but advances in glass manufacture in about 1840 meant that larger panes could be made, and big sheets of glass were substituted so that many Victorian sashes hold just one or two panes.
