Although Victorian and Edwardian houses are still giving good service today, few have their original windows. Most have been fitted with replacement UPVC windows designed to look like the originals.
My mother's written recollections of life in her childhood in the early 1900s frequently mention sash windows. So I wanted to learn more about what they were. This page is about what I discovered.
A 'sash window' is a window in two sections which opens by sliding one or both of the sections up or down over the other. Little effort is required because of an ingenious system of pulleys and counter balancing weights which keep the window open or closed in any position. Each section is known as a 'sash'. The outer one is the top one.
I understand that sash windows were in use as early as the 17th century, and they were commonplace before the onset of the commercial use of plastics in the middle of the 20th century. In their heyday sash windows always had wooden frames.
Each window section (ie the upper and the lower sash) is hung on cords which pass over pulleys and connect to weights which are concealed inside the window frame.
Sometimes the sash cords would snap with wear while they were being opened or closed. Then the window would crash down onto fingers. It was very heavy and could hurt a lot.
Sash windows in the better-off houses and public buildings tended to have chains instead of cords. These, of course, snapped much more rarely.
The weights counterbalance the weight of the window so that it can be raised and lowered with little or no effort and then stays in whatever position it is left in.
The frames of the sash windows were made of wood. So they expanded in damp weather unless they were painted regularly. The expansion changed the fit, so they often stuck. Then in drier weather the wood contracted and the windows rattled around in the wind.
There are projections called 'horns' at the lower edges of the upper sash window - see the sketch.
These horns prevent the top window from sliding down so far behind the lower sash that it can't be reached from inside.