Sash window repairs

Summary: Learn how to replace broken sash cords on a window.

A broken sash cord on a sash window is common. Faced with this problem you may want to consider replacing the traditional weight-and-pulley system with a modern spiral balance mechanism. Fitting instructions will come with the spiral balance system that you buy, but it is important to weigh the sashes before you make your purchase to ensure you get the right size of balance for the window.

Replacing the cords

To replace the cords in a weight-and-pulley system, follow the instructions below.

  • Working from the inside of the building, use the blade of a slot-head screwdriver to prise away the beading holding the bottom sash in place. With care the beading can be removed in one piece.
  • Cut the unbroken sash cord and lift the inner sash clear of the window. It is advisable to replace both sash cords to avoid replacing one, then having to replace the other a few weeks later.
  • If the cord is broken on the outer (top) sash you need to prise away the central staff bead before you can remove it. Then cut the unbroken cord and lift the outer sash clear of the window.
  • The old cords will still be attached to the sashes, which should now be removed. They will be either knotted through retaining holes or nailed or screwed to the sash.
  • At the bottom of the frame on either side there will be two weight covers. These need to be removed to gain access to the weights. Each sash has a weight on both sides of the frame, so there are four weights in total.
  • Detach the old cords from the weights. To calculate the length of new cord for each weight, measure from the top of the window down to the sill. Then add two thirds of this length to the measurement to allow enough spare cord for attaching it to the sash and the weight. 
  • At this point it is a good idea to make sure the pulley mechanisms are running smoothly, applying a little aerosol lubricant to them if they are stiff.
  • To thread the new cord over the pulley tie the end of the cord to a piece of string. Tie a small weight to the other end of the string (a small screw or nail will do as long as it can be fed behind the pulley). Thread the string over the pulley and, as it drops down, it will take the cord with it.
  • Tie the cord to the weight and replace the weight in the frame. Do the same on the other side of the window.
  • Rest the outer sash in the frame on the window ledge, and get a helper to pull the cord down so the weight rises and is just touching the pulley.
  • If the sash has a retaining hole for the cord, thread it through and pull it taught before knotting the end. Do the same on the other side, ensuring the sash sits squarely in the frame.
  • If the cord is attached to the sash with clout nails or galvanised screws, the cord must not be fixed in position too close to the top of the sash. The top nail or screw must be no higher than the distance from the mid point of the pulley to the top of the frame, otherwise the sash will be prevented from sliding to the top of the frame.
  • Check the mechanism works smoothly before refitting the central staff beads.
  • Attach the new cords to the inner (lower) sash employing the same method you used for the outer sash. Having done this, refit the beading around the inner sash.
  • Ensure the inner sash fits squarely in the frame and operates smoothly. If the lower sash rattles in the frame this indicates that there is too big a gap between it and the beading. To rectify this move the beading closer to the frame.
  • Finally, replace the weight covers but do not nail or glue them, as this makes it difficult to gain access to the weights.

Tools needed

  • Slot-head screwdriver
  • Craft knife

Materials needed

  • New Sash cord
  • Aerosol lubricant

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