Timber Sash windows are a beautiful feature in many homes, representing the best in old-world construction. The term 'Timber' refers to the construction of the frame, traditionally made of good solid wood, often pine. These windows are an over and under arrangement, with the individual sashes holding multiple panes of glass, often in two rows. Each pane is separated from the others by thinner slats of wood known as muntins. These beautiful windows saw many innovations during their years of service, and throughout that time multiple forms of opening mechanisms were created.
The basic design of an opening mechanism for these windows involves heavy metal counterweights and pulley system. As the lower sash is raised, the counterweights hung in recessed channels on either side of the window will lower appropriately, holding the sash in place. They are designed in such a way that the windows won't move unless they are moved manually, the weights serving to keep them in exactly the position you set them in. There are multiple problems that can occur with these. If the wood swells or dries out, the tension caused by the friction between the window and its frame can cause the counterweights not to function properly. Similar problems can occur if rot sets in. Perhaps the most inconvenient side effect of this mechanism happens if the cord connected the counterweights to the sash break, resulting in the windows not being able to be properly opened. Repairing this can be more than a little difficult, requiring full deconstruction of the window to get into the channels where the weights are kept to replace the strings, and then getting everything set back in place.
Another method for keeping sash windows opened or closed is the use of compression weatherstripping. This method doesn't work very well with older models of sash windows, as the weight of the wood will easily overcome the tension applied by the weatherstripping. In newer light-weight models made with hollow aluminum frames can use this form of tension based opening mechanism to hold their place in the windows. The benefits of these windows is the weatherstripping serves to keep out drafts and moisture, and the ease of replacement in the event this weatherstripping becomes damaged. When you are looking for a type of window that provides you the best in beautiful construction and a highly efficient method of weather treatment, you might consider a sash window with weatherstripping to keep out the winter cold.
The third common opening mechanism involves the use of springs set into the window frames that provide enough tension to hold the windows in place, but not enough to push them open. These mechanisms are very basic, but work incredibly in the prime of their life. The springs do have the drawback of being susceptible to corrosion, as well as mechanical wear and tear weakening the springs over time. Eventually the springs can give out, making it impossible to keep the window open without something to prop them open. Replacement is, thankfully, simple enough. You need merely replace the springs in the windows, which can be a little tricky, but overall it is a simple fix.
Sash windows are extremely common, and in fact are one of the most recognizable types of windows in the world today. There is something about their old-world elegance that makes them a staple in so many movies trying to represent days gone by, or a home with a long history. A little bit of research will prepare you to take advantage of the beauty in your own home, and keep them working well for many years.