The sliding sash window has vertical moving openers (sashes), produced as 'Double-Hung' sash windows, that is; with top and bottom openers. The sashes run in channels on the window stiles formed by the outer lining, and the internal staff beading, it is then divided into two channels by the parting bead.
The movement of the sashes is aided by cast iron weights, which are hidden from view within the window frame. This is why both sides of the sliding sash window are hollow, a box section.
Built into both top inside faces of the window stiles are pulleys over which the cord that connect the sashes to the weights run. The weights moved down as the window moves up over these pulleys and vice versa. Also, because the weight for each sash is the same, the sashes are balanced and move smoothly within the tracks in which they run preventing them from sticking, and make them lightweight to operate.
This design of window needs to be well maintained for it to be kept in good working order, and care must be taken in particular when painting. It is recommended that the painting of sash windows be done professionally. Despite this, over time the cords can wear, perish, and eventually snap, allowing the weights to drop to the bottom of the window box cavity. This has the effect of making the sashes difficult to operate, heavy, with no control as to their positioning, in which case, the cords will need to be renewed.
Cord renewal requires both sashes to be removed, which is only possible by removing both (side) staff beads. The staff bead is the surround beading that forms the shoulder of the rebate, and can only be removed from the internal side of the window frame for the obvious security reasons. With the beading removed, the internal sash can be removed from the frame.
With this sash removed, you will notice that both edges are grooved to receive the cord, and the cord is fixed into the groove with small galvanised nails. Cut both cords just above the sash, and lower the weights to the bottom of the cavity.
With the internal sash removed, the parting beads that divide the channels can also be removed. This will allow the external sash to be removed in the same way, and the cords cut.
The length of the new cord will need to be determined, and this is done by measuring the distance from the bottom of each sash to the bottom of the cord in the groove as shown on the the drawing on the right. This measurement is then be transferred onto the pulley stiles. The drawing (below left) shows both marks on the stile for the top and bottom sashes. When the stage is reached to cut the cord, the final measurement will be taken from these marks.
At the bottom of each stile, there is what is known as 'Pockets'. These are removable elongated inserts, which when removed; allow access to within the box section of the frame in which the weights are situated. When removed, access the weights, untie the cord and mark each one so that each pair can be re-installed back to their original position when re-cording. To enable the new cord to be introduced into the cavity, a device known as a 'Mouse' will be required. This is simply a piece of lead weight that will simplify the re-cording process. The mouse consists of a small piece of lead about 30mm long, which is rolled up with a length of string within it. The diameter of the lead should be that it can be passed through and over the pulley. The weight of the lead allows it to drop to the bottom of the box section of the window frame, and accessible through the pocket, while at the same time holding the string at the top.
Working from the inside, tie the end of the mouse string to the new sash cord and feed it through the top inner pulley (A), and allow it to drop to the bottom of the cavity (position B), and pull it through. Next, feed the mouse through the opposite top pulley (C) so that the cord runs diagonally and allow it to drop and pull it though pocket (D). From this position, feed the mouse out of the pocket so that it also runs diagonally from corner to corner of the window frame through the outside pulley (E), and down out of pocket (F). Now, feed the mouse through the opposite inside pulley (G), and out of the bottom pocket (H), as illustrated.
The mouse can now be removed from the end of the cord and the fastened to the sash weight. Pull the weight right up to the top, and pin it through the cord into the pulley stile close to the pulley to stop the weight dropping back. The cord can now be cut to the length marked on the pulley stile.
Repeat with the opposite weight at pocket (F), and cut the cord to the length marked on the opposite pulley-stile. Both cords can now be fixed into the grooves at the side of the sash, using the appropriate nails. (Use the same amount of nails that was taken out). At this point, remove the two retaining pins, and raise the sash to the top position, ensuring that it works correctly. The parting bead can then be reinstalled, and the sash tested again. Repeat the process with the inner weights for the inner sash, testing before replacing the staff beading.