The Sash Window Service Ltd. - Lead 'Add Weights'

How to calculate approximate weight requirements:
Typically the glass in a re-glazed sash will be 1mm-2mm thicker than the original material. As a general guide you can estimate the weight of glass thus:

  Weight = 2.5kg per square metre per mm thickness.

Therefore the weight of a 4mm-thick sheet of glass measuring 1m2 is estimated to be: 2.5kg x 1 x 4 = 10kg.

Allow 3kg for a standard 1m2 square wooden sash frame (varies with the wood used) to arrive at an approximate weight requirement of 13kg (approximately 30lbs).

Often it is possible to visually check to see what existing weight you have in the cavities by removing the pocket (without dismantling the entire sash) and work out the difference between what you have and what you need.

To accurately measure the required weight.
Prepare your windows in advance (see the DVD or other instructions) by dismantling the sashes and cleaning off the excess paint.
Using bathroom scales weigh the sashes and order your weights, cords and beadings. Temporarily refit your sashes (without cords) and securely fix in place. On arrival of materials strip down and reassemble correctly.

If you intend to fit double gazed units into an existing sash frame we recommend that you scrap the existing weight and use the largest possible Lead weight. It is necessary to measure the pocket opening for width and height. Then measure the depth and width of the box frame. This will give you a maximum dimension of weight(s). Remember to allow for the waggle board (if it exists) and a minimum 5mm internal gap for the weights to pass each other. The best way to fit large weights is to get one weight about 20mm smaller than the height of the pocket and make up the remaining weight using ‘add ons’. This provides maximum flexibility. If you supply us with the detail dimension we can help work out the best approach and weight requirements: Telephone the workshop on: 01453861025
We can supply complete sets of weights to almost any dimension and length. These weights are square and come with a pre-inserted hook to attach the sash cord.