I nevitably, sash windows cord fray and wear out, and eventually, they will snap. The first step to replacing a sash window cord is understanding the anatomy of the window.
Sash Window Construction
A box sash window operates by counterbalancing the weight of the window panel against corresponding weights attached to a cord and passed over a simple pulley. Old weights are usually iron or lead, and are concealed within a box in the window frame, hence the name Box Sash Windows. There is often a dividing strip within the box, rather charmingly called a wagtail after the bird, to prevent the weights from colliding. Access to the weights is via a removable pocket cut into the inside of the box lining, usually behind wooden shutters.
How to Access the Mechanism
A feature called parting beads is set in grooves which run down the middle of the lining and hold the pockets in place whilst also forming a channel for the top, outer sash. The channel for the inner bottom sash is formed by the parting bead and staff bead, which run around the inside perimeter of the frame.
Use a sharp knife and slice along any paint joints between the staff beads and the box frame. This helps reduce any damage to the paintwork. Gently tap the beads inwards towards the centre of the window using a mallet and blunt chisel. Place the chisel tip into the little recess at the back of the staff bead and start midway along the longest bead, as this gives the most flexion. Once a gap has appeared, the bead can be levered off. Repeat this process for the side and bottom beads, leaving the top staff and parting beads in place. Take any nails from the beads to avoid injury. The beads can be reused, or if they are old and worn or have split, then they will need to be replaced.
Removing the Bottom and Top Sash
Hold and cut the cord just where it pokes out from the bottom of the sash and tie a knot in the end. Let the weight drop slowly down inside the frame until the knot sits at the pulley. Then you can remove the sash. Carefully slice along the paint joints of the top sash and tap the window gently until it is free. If your window has sash horns, then it can help to tap upwards on these. Remove the cords and tie knots just as you did with the bottom sash.
Remove the Pockets
Now that the pockets are visible, use the sharp knife to slice along the paint joints around the pockets and gently lever them out. If they offer resistance, then check for nails or screws. Pockets, like parting beads, are designed to simply fit snugly, but many are nailed or screwed into place over the years.
Remove the Weights
You should be able to see the bottom of the weights hanging in the pocket. Untie the knot and carefully remove the weight.
Balancing the Sashes
The weights and the windows should be equally balanced, and whilst the window is dismantled, this is the perfect opportunity to check. Repairs and heavier glazing can unbalance the windows so they won’t run as well, and this also puts more strain on the cord. Weights and the windows can be weighed separately on the bathroom scales. What are called lead ‘make up’ weights can be used to balance out deficiencies. It’s ideal for the top sash weights to be just a bit heavier, as this will help the sash close tightly.
Replacing the Cords
Pass new cords through the pulleys. You may need to use a ‘mouse’, which is a small weight, small enough to fit through the pulley, tied to the end of a piece of string – ‘the mouse’. This acts as a draw wire to pull the larger sash cord through.
Use a suitable knot or hitch to attach the cord to the weight. Cut the cord leaving around 300mm sticking out from the pulley, and tie a loose knot, so it doesn’t slip back inside the frame. Then it’s just a question of rehanging the top sash, replacing the parting beads and then repeating this for the bottom sash.
There will be an element of restoration and making good depending on how difficult it was to access the mechanism and how much of a repair and restoration opportunity you want to turn this into.
What type of rope should I buy?
Don’t buy cheap rope, as you’ll need to go through the process of replacing it more often. White, 6mm braided marine cord is perfect as it lasts forever and doesn’t stretch. Anything that is even slightly elasticised will eventually fray. Even before the cord snaps, if they become too long, then the top sash will not close properly because the weights have bottomed out.
Replacing broken cords on your sash windows is a great opportunity to undertake restoration and repair. If it all sounds too much like hard work, then why not take advantage of our restoration and repair services? We can work in situ or transport the windows to our workshop for more extensive refurbishment. Take advantage of new lightweight thermal glazing and draught-proofing. We also bespoke manufacture new timber sash windows for both contemporary and period properties with a huge choice of styles, shapes and sizes, the very best of traditional craftsmanship matched with modern materials and techniques.
Contact us to find out more about our sash window repair and restoration services.
