DIY guide to replace sash cords

Do It Yourself Sash Window Cord Replacement

 Should you wish to completely recondition a sash window or simply need to remove the sashes to get large furniture into the property then these guidelines can be utilized.  These guidelines are for the most common sliding box sash windows encountered.  It should be remembered however that not every sash window is exactly the same and regional variations are not uncommon. 

These guidelines are written for work to be undertaken from inside of the property.  This information is given to the best of our ability, but is given expressly without any liability on our part.

How a sash window works

A box sash window operates by counterbalancing the weight of the sash against weights attached to a cord and passed over a pulley. These weights (generally cast iron or lead) travel up and down in a box, concealed within the window frame, hence the name Box Sash Windows. A dividing strip is often suspended within the box to prevent collision of the weights.  
Access to the weights is by means of a removable pocket, usually cut into the inside of the box lining but occasionally found in the box face behind wooden shutters.  
Parting beads are set into grooves running down the length of the linings, holding the pockets in place and separating the top (back) sash into its own channel. The channel for the bottom (front) sash is formed by the Staff Bead running around the perimeter of the lining.

Disassemble Sash Window

Remove the staff beads – Using a sharp knife carefully slice along the paint joint formed between the staff beads and the box frame, this will minimize disruption to the paintwork.   Using a mallet and a blunt chisel (25mm+) gently tap the beads in towards the centre of the window –  The chisel should be sat into the small recess at the back of the staff bead, starting midway along the longest bead.  Once the bead is free it can then be removed being sure to avoid injury on the protruding nails.  Repeat this procedure for the remaining beads.  De-nail the beads and set aside for reuse or disposal.

If new cords are to be fitted: one at a time cut the cord from the bottom sash and tie a knot in the end still attached to the weight, allow the weight to be lowered until the knot is at the pulley:  Remove the sash.  If the cords are not to be replaced then gently remove the pins attaching the cord to the sash (or untie the knot as appropriate) and tie a knot in the cord, slowly allow it to rest at the pulley.  Remove the sash.

Remove the parting beads – Using a sharp knife slice along the paint joint between the parting beads and the box frame.  Gently prise the parting beads from their narrow grooves – again being careful of nails or sharp paint. 

Remove the top sash – If the top sash is inoperable it is usually painted shut, but also check for nails or screws fixing it into place.  Carefully slice along the paint joints with a sharp knife, and tap the sash gently until it is free. BEWARE it may have been fixed shut because of broken cords and might drop when released.  Remove the cords & knot as you did with the bottom sash.

Remove the Pockets – The pockets should now be visible, using a sharp knife slice along the paint joints around the pockets and gently prise them out. (Traditionally pockets and parting beads are a snug fit, requiring no fixings but over the years many have been pinned/screwed into place).

Remove the weights – The weights should be visible in the pocket, untie the knot suspending it and carefully remove it.  Be very careful when handling weights as they can easily cause an injury, it is advisable to wear protective gloves.

Repairs – Carefully inspect the sashes and the frame for any damage.  Chop out all damaged wood and repair with an epoxy filler or splice in fresh timber.  Do not forget to treat the effected area with a multi purpose wood preservative.  If any of the sash joints are loose re-secure them by gluing & re wedging the tenons.   2 part epoxy filler also helps to bond open joints.

Preparing the frame – Using a scraper remove any excessive paint build up and sand the inner surfaces of the box ready for repainting. Ensure that all of the pulleys are free rolling, use a spray lubricant on the bearing to eliminate squeaking.  Prime/undercoat any bare wood before repainting the frame, acrylic paints are well suited to this purpose because of their fast drying times.  Ensure exterior grade paint is used.

Preparing the sashes – You may also decide to repair broken glass and/or re-paint the sashes whilst they are out.  Any missing or loose putty should also be replaced.

 

Reassemble Sash Window

Balancing the sashes – For the sashes to slide easily it is important that the weights and sashes are balanced. Weigh the pair of weights and then the sash (ensuring that any glass repairs are already complete), bathroom scales are suitable. Adjust deficiencies in the sash weights with lead ‘make up’ weights.  It is recommended that the top sash weighting be a couple of pounds over weight to ensure a tight fit at the head.

Replacing the cords – Pass replacement sash cords through the pulleys and down out of the pocket.  Often a mouse is required – Simply attach a small weight to the end of a piece of string (the mouse), drop it over the pulley and out of the pocket use this as a draw wire to then pull  the larger sash cord through.  Securely attach the weight with a suitable knot, including any make up weights required and replace into the frame.  Cut the cord leaving approx. 300mm protruding from the pulley & tie a loose knot to prevent it slipping back inside the frame.  If there is no dividing strip between the weights it may be necessary to cut a strip of hardboard or thin plastic sheet and pass it up between the weights and pulleys. This strip prevents the weights from snagging each other.  Carefully replace the pockets.

Re-hanging the top sash – Individually pull the rear cords until the weight is at the top of the box, against the pulley.  Pin the cord to the box frame, leaving the head protruding for easy removal – Put the pin where the staff bead will sit & well above the height of the sash meeting rails.  The weight is now suspended allowing you to attach the cord to the sash. Sit the sash in position and tilt forward to fix cords.  Cords are fixed either by being pinned into a groove (1” carpet tacks are ideal) or suspended on a knot.  For knots simply pass the cord down the channel & through the hole. Tie a knot large enough not to pull back through, leave a short tail and cut of excess cord.   For pinned cords ensure that tacks are low enough to enable the pulley to pull the sash to the top of the box without snagging, (If the distance between the top of the box and the bottom of the pulley is X cm make sure your top tack is X+20 mm from the top of the sash.)  Remove the pins attaching the cords to the frame and allow the top sash to slide into place.  Pull the sash through it’s full travel, if excessive side to side movement occurs then the sashes should be packed accordingly using timber fillets; if it binds it will need to be planed down.  NOTE: If the window is wider than it is tall then the length of the cords may have to be reduced which will also reduce the opening of the sash.

Replace the parting beads – Parting beads may need to be planed to ensure that they fit snug in their grooves.  Seal any gaps with decorators caulk.

• •   The parting beads  that we supply with built in draught seals are fitted in 2 pieces.  Measure the distance from the top of the sash to the centre of the meeting rails and fit with the seal facing outside.  The parting bead is reversed for the bottom sash, with the seal facing inwards.  The join is not visible when work is complete but a tight fit should be ensured reduced draughts.

Replace bottom sash – Re-hang the bottom sash as you did with the top.  The bottom sash may need planing so as to bring the meeting rails of the sashes level.

Replace staff beads – Either re-fix the original beads in place or measure the 4 dimensions of the box and cut replacement staff beads to suit. These should be securely nailed into place, ensuring that they are not so close as to restrict sash operation and not so wide as to allow the sash to rattle.  Use decorators caulk to seal the gap between the staff bead and box, this will further help to reduce draughts. 

Hardware – Check that catches and locks are correctly aligned and fully functioning

Lubricate – Use of silicone spray on the running stiles will help to improve performance.

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