Different to the modern window frame the sliding sash window does not have hinges, rather, it has vertical sliding openers (sashes), produced as 'Double-Hung' sash windows, that is; with top and bottom openers. The sashes run in a wide channel within the window stiles which is formed by the outer timber lining, and the internal staff beading, which is then divided into two channels by a parting bead.
For the sashes to be able to move smoothly within the side channels, cast iron weights are present on each side of both sashes. The weights are connected to the sashes by a cord, so that the sashes actually hang from the cords, and when raised or lowered the weights which are the same weight always keep the frame of the sash in the correct position so that it does not rock from side to side and stick. The weights also assist the user by taking up most of the weight of the sash when being elevated.
As you may already appreciate, a great deal of thought went into this design, which enabled everything to work perfectly.
For the sliding sash window frame to be able to accommodate the weights, the side of the window frame is hollow, and divided into two compartments by the wagtail. Built into the top inside face of the stile are two pulleys over which the cord runs and connect the sashes to the weights. These weights move down as the window moves up, and vice versa.
In the past, the sliding sash window was the norm, but has since declined and is now rarely seen, being superseded by the modern window frame with its simple frame design and hinged opening sashes.
One of the reasons for their decline is to do with the amount of work required in their manufacture, and the amount of different components in their make-up. In addition to this, they need regular maintenance to keep them working smoothly. This would mean the maintenance of the pulleys, and the renewal of the cord. Lack of maintenance will bring about many problems, such as worn and snapping cords resulting in the weight dropping to the bottom of the window box cavity. Poor maintenance of the pulleys and the incorrect painting procedure also causes the sashes to stick making them difficult to move. They are also liable to rattle in the wind as well as being draughty.
I'm happy to say that in recent times there has been a revival in this type of window, with many newly built properties installing them to reflect the retro style. There are manufacturers who are now producing them to the original specification, and provide a renovation service; providing added features such as draught proofing and security.
I like the old sash window for a number of reasons; such as its interesting design features and its practicality. I also think it is of interest how this old classic has survived the test of time and is still with us today all be it in lesser numbers.