There are quite a few ways that a snapped sash cord can leave you with a dropped sash that won’t open and shut properly.
How the Cord System Works
Each sash is balanced on two cords, which run over a pulley and are attached to a weight inside the frame (a lead or cast-iron weight). The sashes balance correctly and move up and down and side to side, level and straight, when both sides are correct.
Spotting a Broken Cord
A sash that has dropped and won’t open, or is leaning to one side under its own weight is a clear sign of a broken cord. Check the side channels for signs of wear, for example fraying or that one of the cords is missing.
What the Repair Involves
First the staff bead is removed in order to allow the sash to be removed from the frame. Next, the small pocket piece at the bottom of the frame is opened up in order to allow the weights to be retrieved from within the frame. The new cord (wax-coated cotton or polyester) is then threaded over the pulley at the bottom of the frame and then knotted around the weight within the frame. Finally, the cord is nailed into the groove at the bottom edge of the sash.
Replace Both Cords Together
Many experienced Sash Window Repair Kensington companies would advise replacing both cords for the sash should one only have snapped. The other cord for the sash will be worn to a similar extent and could fail very quickly if left in place.
Test Before the Job Is Finished
The whole thing should be tested up and down before you let the joiner go – it should travel smoothly up and down and stay open at any height without drifting. For information on how to look after your old joinery, see the SPAB’s non-commercial, detailed information on old timber windows. A useful reference for Sash Window Repair Kensington is https://www.sashwindowpreservation.co.uk/services/sash-window-repair/london/kensington/.
A well-replaced cord should give many years of smooth, balanced movement.
